Posts Tagged ‘3-D bioprinting’

3-D Printed Organs

Curator: Larry H. Bernstein, MD, FCAP




The Future of 3-D Printing in Medicine

Today’s 3-D printed plastic models of hearts may one day translate into on-demand printed, functional replacement organs


A 3-D printed vessel-like lumen made from living cells as part of the research at The South Carolina Project for Organ Biofabrication.

Science fiction offers a lot of ideas for creating new body parts on demand, and the advancement of 3-D printing (also called additive manufacturing) is slowly translating this idea into science fact. Today, the 3-D printed anatomic models created from patient computed tomography (CT), magnetic resonance imaging (MRI) or 3-D ultrasound imaging datasets are used for education and to plan and navigate complex procedures. These models are used to teach about complex or rare cardiac or congenital conditions that up until recently could only be seen using examples extracted from cadavers. Today, anatomical models of rare cardiac anatomy can be printed on demand from CT scans of surviving patients.  That concept can now be translated into 3-D printing of implantable devices customized to a specific patient using their imaging. Experts at several medical conferences are also saying printing functional biological replacement tissues is already in development.

Video interview with Dee Dee Wang, M.D., FACC, FASE, Henry Ford Hospital, explaining the use of 3-D printing to aid procedural planning and guidance in complex structural heart cases.

See video examples of 3-D printed hearts as part of the editor’s choice of the most innovative new teachnology at ACC.16. – See more at: http://www.dicardiology.com/article/future-3-d-printing-medicine?eid=333021707&bid=1408765#sthash.M7AYV16i.dpuf

Early Experience Printing Implantable Devices Printed 3-D models are currently used for surgical planning in complex cases, especially in pediatric congenital heart procedures, said Richard G. Ohye, M.D., professor of cardiac surgery, head, section of pediatric cardiovascular surgery, surgical director, pediatric cardiovascular transplant program, co-director, Michigan Congenital Heart Center, C.S. Mott Children’s Hospital, Ann Arbor, Mich. However, he explained 3-D printing will soon allow the creation of customized implantable medical devices, including actual tissue or vessel replacements.  In fact, 3-D printed devices are already being used on a small scale.

He presented a case of a three-month-old patient whose airway was underdeveloped and required a splint to hold it open. The patient underwent a CT scan and a 3-D reconstruction of the airway allowed doctors to create a virtual airway splint implant customized to fit into the small anatomy. The design included a “C”-shaped tube that had numerous holes to use as suture anchor points. The shape was designed to allow it to expand outward as the patient grew. They then 3-D printed the splint from bioresorbable plastic and implanted it in the patient. He said the material it was made from is expected to dissolve within three to four years.

The Finnish dental equipment maker Planmeca recently introduced a 3-D printer that allows dental laboratories and large clinics to create dental splints, models and surgical guides. In the near future, the Planmeca Creo printer will also support the creation of intricate, customized temporary fillings. The jump to printing full organs to transplant is much more complex, but the groundwork is being laid today. Ohye said engineered heart tissue created using cardiac stem cells has already been created, but it is limited to a size of about 200 microns. Anything larger requires blood vessels to keep the cells alive, he explained.

3-D Printing of Biological Tissue Implants Research is being conducted to enable 3-D printing of blood vessels, where cells are deposited by the robotically driven printer in patterns that build up layer-by-layer to create a lumen. That same concept is being tested at a few centers to create 3-D print heart valves. Ohye said the process currently being investigated used a printed matrix of biocompatible material, in which stem cells can then be deposited. If the process can be worked out to create engineered, printed organs, these might be used to create benchtop model organs for new drug testing in the next few years. Implantable 3-D printed living organs for transplant into human patients are also a very real possibility.

“Bioprinting is likely to be a huge field for the future of medicine,” said Roger Markwald, Ph.D., director, Cardiovascular Developmental Biology Center, Medical University of South Carolina. He is involved with The South Carolina Project for Organ Biofabrication, one of the groups at the forefront of 3-D bioprinting research. He explained there are too few organ donors to meet demand and there is an even greater need for soft tissues for reconstructive surgeries for things such as injuries, burns, infections, tumor resections and congenital malformations.  “There are too few organ donors to meet the needs,” Markwald said. “At least 21 people die each day because of the lack of implants.”  This organ shortage might be solved in the future by bioprinting organs on demand.

Biomaterials can be printed using current technology, but there is a fatal flaw. “The Achilles heel of tissue engineering today is the need to create vascularity in the structure, and that has been the focus of what we have been trying to do,” Markwald said.   The key to printing vascularizable micro-organs may involve chemical modifications of alginate hydrogels. Markwald’s lab created an oxidized alginate, which is biodegradable and provides stability for 3-D bioprinting. It also is bioactive, allowing cells to migrate and remodel. They created “plug and play” molds to prepare micro-organ constructs for surgical implantation. These are made with the biodegradable alginate, which contain small molecules to promote host vascular in-growth and suppress inflammatory responses.

Bioprinting is enabled using a “biopaper” made of bioresorbable hydrogels. These allow printing of the cells against gravity and allow the cells to grow, interact and function physiologically. Markwald said research is leading to the development of hydrogels specific to each type of organ tissue.  The “bioink” is made from 300 micron diameter spheroids that contain between 8,000-12,000 autologous adipose-derived stem cells. He said it takes about 7 million cells to make 840 spheroids, and it takes thousands of these spheroids to print a 1 mm cube.

Just as 3-D printing allows simultaneous printing of several different colors of materials to build a color 3-D model, bioprinting is being developed to allow use of several different cell types to create complex tissue units.  “Eventually we will be able to make functional hearts or livers,” Markwald said. “What we can print right now are cardiac patches and small- to medium-sized blood vessels, skin tissue, soft tissue (adipose, muscle) for reconstructive surgery, and vascularized micro-organs that can be grown in a bioreactor and used to supplement the function of a diseased organ like the liver.”

Creating 3-D Printable Files Creating files for 3-D printing from medical imaging datasets starts with good imaging, said Shuai Leng, Ph.D., associate professor of medical physics, Mayo Clinic, Rochester, Minn. “If you start with garbage in, you get garbage out, so you need good image quality,” he stressed.   To create a usable 3-D file, he suggests using 0.6 mm thin imaging slices. This allows for very smooth surfaces. By comparison, he said use of 6 mm slices will make the printed object very rough and textured, appearing pixelated, when it is printed in 3-D.  He said dual-energy CT is great for 3-D printing because it can easily exclude bone so only blood vessels or soft tissue remain in the image area.

Metal implants commonly cause problems when creating 3-D printing files, but dual-energy systems have metal artifact reduction software to separate the metal and artifacts from the anatomy to allow creation of better models.  When using 3-D models for procedural planning and navigation, you need to ensure the precision of the model by using U.S. Food and Drug Administration (FDA)-cleared 3-D printing software, such as programs offered by Stratasys or Materialise. The resulting printed models also should be compared to the original images to ensure quality control. Before printing, images should be checked in three planes and approved by a radiologist or the ordering physician.  The final imaging files are converted into STL/CAD files that can be read by the 3-D printers and translated into the final 3-D object.

Legal Considerations Regarding 3-D printing The field of 3-D printing comes with a new set of legal questions hospitals using the technology will need to consider, said Bruce Kline, a technology licensing manager who oversees patents for new technology developed at Mayo Clinic. For starters, he said the STL files printers use are a lot like MP3 music files, in that they can be protected under copyright and require licensing to use. Copyright violations can occur if a purchased STL anatomical model file for rare disease is illegally shared with another institution that did not purchase the file from the vendor that created the file. Under the law, if a device has a functional use it falls under patent law. If it is not functional, it falls under copyright law. Kline said most medical 3-D printing for educational models and complex anatomy evaluation currently falls under copyright. But, he said that will rapidly change in the coming years as customizable 3-D printable medical devices see wider use. Additive manufacturing allows the creation of patient-specific devices at the point of care. Kline said an interesting fact is that these devices are FDA 510(k)-exempt if produced by a hospital instead of a medical device vendor. He said this blurs the lines between traditional vendor relationships, since the hospital can now become the manufacturer. However, if a hospital makes a device, it also becomes liable for it.

He advised that it might be better for a commercial vendor to make the device for the hospital so the vendor assumes the liability of the device.   Custom-made medical devices are also exempt under FDA regulations, Kline said. So, if a physician creates or modifies a device to meet the clinical needs of a specific patient’s anatomy, he said it is acceptable to use under current FDA rules. This may leave the door wide open for use of 3-D printed devices that are customized for each patient using their own 3-D imaging datasets.  It is possible printable device files may become available in the next few years to customize and print on demand. However, Kline said it will be much more difficult to enforce patents on these types of devices. He explained if someone makes one or two devices, there is no economical way for the creator of those device files to go after the user/maker of unlicensed copies of the device to claim lost profits. Currently, Kline said surgical planning models created with 3-D printing are not reimbursable. No CPT code exists for their use, because he said CPT codes are based on clinical trial data showing clinical efficacy to justify reimbursement.

Proposed FDA Guidance for 3-D Printing   In May, the FDA released the draft guidance “Technical Considerations for Additive Manufactured Devices,” for public comment. It is a leapfrog guidance document to provide FDA’s initial thoughts on technical considerations specific to 3-D printed devices. Specifically, this draft guidance outlines technical considerations associated with additive manufacturing processes, and the testing and characterization for final finished devices fabricated using 3-D printing. It is intended to serve as a mechanism by which the agency can share initial thoughts regarding the content of premarket submissions for emerging technologies and new clinical applications that are likely to be of public health importance very early in product development. The draft document was created following a fall 2014 workshop where 3-D printing experts discussed all the facets of 3-D printing and attempted to anticipate the issues and questions that will be raised as 3-D printable devices begin to come before the FDA for review in the coming years. 

The FDA notes that in medical device applications, 3-D printing has the advantage of facilitating the creation of anatomically matched devices and surgical instrumentation by using a patient’s own medical imaging. The FDA said another advantage is the ease in fabricating complex geometric structures, allowing the creation of engineered open lattice structures, tortuous internal channels and internal support structures that would not be easily made or possible using traditional manufacturing approaches.  However, the FDA stated the unique aspects of the printing process, such as the layer-wise fabrication and the relative lack of history of medical devices manufactured using 3-D printing techniques, pose challenges in determining optimal characterization and assessment methods for the final finished device. There are also questions as to the optimal process validation and verification methods for these devices. The FDA is gathering public feedback on the draft document through August, 2016. The draft document can be found online at www.fda.gov/ucm/groups/fdagov-public/@fdagov-meddev-gen/documents/document/ucm499809.pdf

Partnerships Make 3-D More Accessible The setup and maintenance costs for 3-D printing are more involved than many hospitals want to get involved with. This is especially true at centers where there is very limited application. This has led to partnerships between advanced imaging vendors and 3-D printer vendors to create contract services for one-off printing projects.  Advanced visualization software company Vital Images announced a partnership with 3-D printer company Stratasys at the Radiological Society of North America (RSNA) 2015 annual meeting. They created the industry’s first print-on-demand service using Vital’s Vitrea advanced visualization software and Stratasys’ 3-D printing services. Vital Images’ software takes patient scans and converts them into STL files that can be sent directly to a 3-D printer, improving workflow efficiency and 3-D printing accessibility.

GE Healthcare is working with 3-D printer vendor Materialise to develop a software package that will allow the easy creation of 3-D printable files from GE 3-D ultrasound sound systems. GE hopes to have commercial product launch for this technology later in 2016.  Materialise already offers its Mimics Innovation Suite software to create 3-D printer files from medical imaging. Its latest version includes the ability to create images not only from MRI and CT datasets, but also from fluoroscopic imaging from C-arms. It also includes a virtual X-ray tool to allow engineers to create projects to find the optimal angle for 2-D/3-D registration. This allows for an evaluation of the 3-D position of bones and implants without a post-operative CT or MRI scan. It has an automated heart segmentation tool to easily separate the cardiovascular anatomy for advanced research and analyses. The vendor said on a good quality dataset, segmentation now requires only a few mouse clicks rather than several hours of tedious work.

Editor’s Choice of the Most Innovative Trends and Technologies ACC.16 – See more at: http://www.dicardiology.com/article/future-3-d-printing-medicine?eid=333021707&bid=1408765#sthash.M7AYV16i.dpuf

Stratasys to Present Power of 3-D Printing at HIMSS 2016 – See more at: http://www.dicardiology.com/article/future-3-d-printing-medicine?eid=333021707&bid=1408765#sthash.M7AYV16i.dpuf


Selecting the Right Material for 3D Printing

This industrial 3D printing white paper explores the properties of thermoplastic and metal materials available with direct metal laser sintering, selective laser sintering and stereolithography technologies. It also includes a quick-reference guide of material attributes that can steer you toward the proper grade.


Click to access 3D-Printing-Materials-WP-US-Final.pdf

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Update on FDA Policy Regarding 3D Bioprinted Material

Curator: Stephen J. Williams, Ph.D.

Last year (2015) in late October the FDA met to finalize a year long process of drafting guidances for bioprinting human tissue and/or medical devices such as orthopedic devices.  This importance of the development of these draft guidances was highlighted in a series of articles below, namely that

  • there were no standards as a manufacturing process
  • use of human tissues and materials could have certain unforseen adverse events associated with the bioprinting process

In the last section of this post a recent presentation by the FDA is given as well as an excellent  pdf here BioprintingGwinnfinal written by a student at University of Kentucky James Gwinn on regulatory concerns of bioprinting.

Bio-Printing Could Be Banned Or Regulated In Two Years

3D Printing News January 30, 2014 No Comments 3dprinterplans







Cross-section of multi-cellular bioprinted human liver tissue Credit: organovo.com

Bio-printing has been touted as the pinnacle of additive manufacturing and medical science, but what if it might be shut down before it splashes onto the medical scene. Research firm, Gartner Inc believes that the rapid development of bio-printing will spark calls to ban the technology for human and non-human tissue within two years.

A report released by Gartner predicts that the time is drawing near when 3D-bioprinted human organs will be readily available, causing widespread debate. They use an example of 3D printed liver tissue by a San Diego-based company named Organovo.

“At one university, they’re actually using cells from human and non-human organs,” said Pete Basiliere, a Gartner Research Director. “In this example, there was human amniotic fluid, canine smooth muscle cells, and bovine cells all being used. Some may feel those constructs are of concern.”


Bio-printing uses extruder needles or inkjet-like printers to lay down rows of living cells. Major challenges still face the technology, such as creating vascular structures to support tissue with oxygen and nutrients. Additionally, creating the connective tissue or scaffolding-like structures to support functional tissue is still a barrier that bio-printing will have to overcome.

Organovo has worked around a number of issues and they hope to print a fully functioning liver for pharmaceutical industry by the end of this year.  “We have achieved thicknesses of greater than 500 microns, and have maintained liver tissue in a fully functional state with native phenotypic behavior for at least 40 days,” said Mike Renard, Organovo’s executive vice president of commercial operations.

clinical trails and testing of organs could take over a decade in the U.S. This is because of the strict rules the U.S. Food and Drug Administration (FDA) places on any new technology. Bio-printing research could outplace regulatory agencies ability to keep up.

“What’s going to happen, in some respects, is the research going on worldwide is outpacing regulatory agencies ability to keep up,” Basiliere said. “3D bio-printing facilities with the ability to print human organs and tissue will advance far faster than general understanding and acceptance of the ramifications of this technology.”

Other companies have been successful with bio-printing as well. Munich-based EnvisionTEC is already selling a printer called a Bioplotter that sells for $188,000 and can print 3D pieces of human tissue. China’s Hangzhou Dianzi University has developed a printer called Regenovo, which printed a small working kidney that lasted four months.

“These initiatives are well-intentioned, but raise a number of questions that remain unanswered. What happens when complex enhanced organs involving nonhuman cells are made? Who will control the ability to produce them? Who will ensure the quality of the resulting organs?” Basiliere said.

Gartner believes demand for bio-printing will explode in 2015, due to a burgeoning population and insufficient levels of healthcare in emerging markets. “The overall success rates of 3D printing use cases in emerging regions will escalate for three main reasons: the increasing ease of access and commoditization of the technology; ROI; and because it simplifies supply chain issues with getting medical devices to these regions,” Basiliere said. “Other primary drivers are a large population base with inadequate access to healthcare in regions often marred by internal conflicts, wars or terrorism.”

It’s interesting to hear Gartner’s bold predictions for bio-printing. Some of the experts we have talked to seem to think bio-printing is further off than many expect, possibly even 20 or 30 years away for fully functioning organs used in transplants on humans. However, less complicated bio-printing procedures and tissue is only a few years away.


FDA examining regulations for 3‑D printed medical devices

Renee Eaton Monday, October 27, 2014


The official purpose of a recent FDA-sponsored workshop was “to provide a forum for FDA, medical device manufacturers, additive manufacturing companies and academia to discuss technical challenges and solutions of 3-D printing.” The FDA wants “input to help it determine technical assessments that should be considered for additively manufactured devices to provide a transparent evaluation process for future submissions.”

Simply put, the FDA is trying to stay current with advanced manufacturing technologies that are revolutionizing patient care and, in some cases, democratizing its availability. When a next-door neighbor can print a medical device in his or her basement, it clearly has many positive and negative implications that need to be considered.

Ignoring the regulatory implications for a moment, the presentations at the workshop were fascinating.

STERIS representative Dr. Bill Brodbeck cautioned that the complex designs and materials now being created with additive manufacturing make sterilization practices challenging. For example, how will the manufacturer know if the implant is sterile or if the agent has been adequately removed? Also, some materials and designs cannot tolerate acids, heat or pressure, making sterilization more difficult.

Dr. Thomas Boland from the University of Texas at El Paso shared his team’s work on 3-D-printed tissues. Using inkjet technology, the researchers are evaluating the variables involved in successfully printing skin. Another bio-printing project being undertaken at Wake Forest by Dr. James Yoo involves constructing bladder-shaped prints using bladder cell biopsies and scaffolding.

Dr. Peter Liacouras at Walter Reed discussed his institution’s practice of using 3-D printing to create surgical guides and custom implants. In another biomedical project, work done at Children’s National Hospital by Drs. Axel Krieger and Laura Olivieri involves the physicians using printed cardiac models to “inform clinical decisions,” i.e. evaluate conditions, plan surgeries and reduce operating time.

As interesting as the presentations were, the subsequent discussions were arguably more important. In an attempt to identify and address all significant impacts of additive manufacturing on medical device production, the subject was organized into preprinting (input), printing (process) and post-printing (output) considerations. Panelists and other stakeholders shared their concerns and viewpoints on each topic in an attempt to inform and persuade FDA decision-makers.

An interesting (but expected) outcome was the relative positions of the various stakeholders. Well-established and large manufacturers proposed validation procedures: material testing, process operating guidelines, quality control, traceability programs, etc. Independent makers argued that this approach would impede, if not eliminate, their ability to provide low-cost prosthetic devices.

Comparing practices to the highly regulated food industry, one can understand and accept the need to adopt similar measures for some additively manufactured medical devices. An implant is going into someone’s body, so the manufacturer needs to evaluate and assure the quality of raw materials, processing procedures and finished product.

But, as in the food industry, this means the producer needs to know the composition of materials. Suppliers cannot hide behind proprietary formulations. If manufacturers are expected to certify that a device is safe, they need to know what ingredients are in the materials they are using.

Many in the industry are also lobbying the FDA to agree that manufacturers should be expected to certify the components and not the additive manufacturing process itself. They argue that what matters is whether the device is safe, not what process was used to make it.

Another distinction should be the product’s risk level. Devices should continue to be classified as I, II or III and that classification, not the process used, should determine its level of regulation.



Will the FDA Regulate Bioprinting?

Published by Sandra Helsel, May 21, 2014 10:20 am

(3DPrintingChannel) The FDA currently assesses 3D printed medical devices and conventionally made products under the same guidelines, despite the different manufacturing methods involved. To receive device approval, manufacturers must prove that the device is equivalent to a product already on the market for the same use, or the device must undergo the process of attaining pre-market approval. However, the approval process for 3D printed devices could become complicated because the devices are manufactured differently and can be customizable. Two teams at the agency are now trying to determine how approval process should be tweaked to account for the changes.

3D Printing and 3D Bioprinting – Will the FDA Regulate Bioprinting?

This entry was posted by Bill Decker on May 20, 2014 at 8:52 am










The 3d printing revolution came to medicine and is making people happy while scaring them at the same time!

3-D printing—the process of making a solid object of any shape from a digital model—has grown increasingly common in recent years, allowing doctors to craft customized devices like hearing aids, dental implants, and surgical instruments. For example, University of Michigan researchers last year used a 3-D laser printer to create an airway splint out of plastic particles. In another case, a patient had 75% of his skull replaced with a 3-D printed implant customized to fit his head. The 3d printing revolution came to medicine and is making people happy while scaring them at the same time!

Printed hearts? Doctors are getting there
FDA currently treats assesses 3-D printed medical devices and conventionally made products under the same guidelines, despite the different manufacturing methods involved. To receive device approval, manufacturers must prove that the device is equivalent to a product already on the market for the same use, or the device must undergo the process of attaining pre-market approval.

“We evaluate all devices, including any that utilize 3-D printing technology, for safety and effectiveness, and appropriate benefit and risk determination, regardless of the manufacturing technologies used,” FDA spokesperson Susan Laine said.
However, the approval process for 3-D printed devices could become complicated because the devices are manufactured differently and can be customizable. Two teams at the agency now are trying to determine how approval process should be tweaked to account for the changes:


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The Stuff of Innovation – 3D Bioprinting and FDA’s Possible Reorganization

Weil Product Liability Monitor on September 10, 2013 ·

Posted in News

Contributing Author: Meghan A. McCaffrey

With 3D printers, what used to exist only in the realm of science fiction — who doesn’t remember the Star Trek food replicator that could materialize a drink or meal with the mere press of a button — is now becoming more widely available with  food on demand, prosthetic devices, tracheal splintsskull implants, and even liver tissue all having recently been printed, used, implanted or consumed.  3D printing, while exciting, also presents a unique hybrid of technology and biology, making it a potentially unique and difficult area to regulate and oversee.  With all of the recent technological advances surround 3D printer technology, the FDA recently announced in a blog post that it too was going 3D, using it to “expand our research efforts and expand our capabilities to review innovative medical products.”  In addition, the agency will be investigating how 3D printing technology impacts medical devices and manufacturing processes.  This will, in turn, raise the additional question of how such technology — one of the goals of which, at least in the medical world,  is to create unique and custom printed devices, tissue and other living organs for use in medical procedures — can be properly evaluated, regulated and monitored.
In medicine, 3D printing is known as “bioprinting,” where so-called bioprinters print cells in liquid or gel format in an attempt to engineer cartilage, bone, skin, blood vessels, and even small pieces of liver and other human tissues [see a recent New York Times article here].  Not to overstate the obvious, but this is truly cutting edge science that could have significant health and safety ramifications for end users.  And more importantly for regulatory purposes, such bioprinting does not fit within the traditional category of a “device” or a “biologic.”  As was noted in Forbes, “more of the products that FDA is tasked with regulating don’t fit into the traditional categories in which FDA has historically divided its work.  Many new medical products transcend boundaries between drugs, devices, and biologics…In such a world, the boundaries between FDA’s different centers may no longer make as much sense.”  To that end, Forbes reported that FDA Commissioner Peggy Hamburg announced Friday the formation of a “Program Alignment Group” at the FDA whose goal is to identify and develop plans “to best adapt to the ongoing rapid changes in the regulatory environment, driven by scientific innovation, globalization, the increasing complexity of regulated products, new legal authorities and additional user fee programs.”

It will be interesting to see if the FDA can retool the agency to make it a more flexible, responsive, and function-specific organization.  In the short term, the FDA has tasked two laboratories in the Office of Science and Engineering Laboratories with investigating how the new 3D technology can impact the safety and efficacy of devices and materials manufactured using the technology.  The Functional Performance and Device Use Laboratory is evaluating “the effect of design changes on the safety and performance of devices when used in different patient populations” while the Laboratory for Solid Mechanics is assessing “how different printing techniques and processes affect the strength and durability of the materials used in medical devices.”  Presumably, all of this information will help the FDA evaluate at some point in the future whether a 3D printed heart is safe and effective for use in the patient population.

In any case, this type of hybrid technology can present a risk for companies and manufacturers creating and using such devices.  It remains to be seen what sort of regulations will be put in place to determine, for example, what types of clinical trials and information will have to be provided before a 3D printer capable of printing a human heart is approved for use by the FDA.  Or even on a different scale, what regulatory hurdles (and on-going monitoring, reporting, and studies) will be required before bioprinted cartilage can be implanted in a patient’s knee.  Are food replicators and holodecks far behind?


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FDA Plans Meeting to Explore Regulation, Medical Uses of 3D Printing Technology

Posted 16 May 2014 By Alexander Gaffney, RAC

The US Food and Drug Administration (FDA) plans to soon hold a meeting to discuss the future of regulating medical products made using 3D printing techniques, it has announced.



3D printing is a manufacturing process which layers printed materials on top of one another, creating three-dimensional parts (as opposed to injection molding or routing materials).

The manufacturing method has recently come into vogue with hobbyists, who have been driven by several factors only likely to accelerate in the near future:

  • The cost of 3D printers has come down considerably.
  • Electronic files which automate the printing process are shareable over the Internet, allowing anyone with the sufficient raw materials to build a part.
  • The technology behind 3D printing is becoming more advanced, allowing for the manufacture of increasingly durable parts.

While the technology has some alarming components—the manufacture of untraceable weapons, for example—it’s increasingly being looked at as the future source of medical product innovation, and in particular for medical devices like prosthetics.

Promise and Problems

But while 3D printing holds promise for patients, it poses immense challenges for regulators, who must assess how to—or whether to—regulate the burgeoning sector.

In a recent FDA Voice blog posting, FDA regulators noted that 3D-printed medical devices have already been used in FDA-cleared clinical interventions, and that it expects more devices to emerge in the future.

Already, FDA’s Office of Science and Engineering laboratories are working to investigate how the technology will affect the future of device manufacturing, and CDRH’s Functional Performance and Device Use Laboratory is developing and adapting computer modeling methods to help determine how small design changes could affect the safety of a device. And at the Laboratory for Solid Mechanics, FDA said it is investigating the materials used in the printing process and how those might affect durability and strength of building materials.

And as Focus noted in August 2013, there are myriad regulatory challenges to confront as well. For example: If a 3D printer makes a medical device, will that device be considered adulterated since it was not manufactured under Quality System Regulation-compliant conditions? Would each device be required to be registered with FDA? And would FDA treat shared design files as unauthorized promotion if they failed to make proper note of the device’s benefits and risks? What happens if a device was never cleared or approved by FDA?

The difficulties for FDA are seemingly endless.

Plans for a Guidance Document

But there have been indications that FDA has been thinking about this issue extensively.

In September 2013, Focus first reported that CDRH Director Jeffery Shuren was planning to release a guidance on 3D printing in “less than two years.”

Responding to Focus, Shuren said the guidance would be primarily focused on the “manufacturing side,” and probably on how 3D printing occurs and the materials used rather than some of the loftier questions posed above.

“What you’re making, and how you’re making it, may have implications for how safe and effective that device is,” he said, explaining how various methods of building materials can lead to various weaknesses or problems.

“Those are the kinds of things we’re working through. ‘What are the considerations to take into account?'”

“We’re not looking to get in the way of 3D printing,” Shuren continued, noting the parallel between 3D printing and personalized medicine. “We’d love to see that.”

Guidance Coming ‘Soon’

In recent weeks there have been indications that the guidance could soon see a public release. Plastics News reported that CDRH’s Benita Dair, deputy director of the Division of Chemistry and Materials Science, said the 3D printing guidance would be announced “soon.”

“In terms of 3-D printing, I think we will soon put out a communication to the public about FDA’s thoughts,” Dair said, according to Plastics News. “We hope to help the market bring new devices to patients and bring them to the United States first. And we hope to play an integral part in that.”

Public Meeting

But FDA has now announced that it may be awaiting public input before it puts out that guidance document. In a 16 May 2014 Federal Register announcement, the agency said it will hold a meeting in October 2014 on the “technical considerations of 3D printing.”

“The purpose of this workshop is to provide a forum for FDA, medical device manufacturers, additive manufacturing companies, and academia to discuss technical challenges and solutions of 3-D printing. The Agency would like input regarding technical assessments that should be considered for additively manufactured devices to provide a transparent evaluation process for future submissions.”

That language—”transparent evaluation process for future submissions”—indicates that at least one level, FDA plans to treat 3D printing no differently than any other medical device, subjecting the products to the same rigorous premarket assessments that many devices now undergo.

FDA’s notice seems to focus on industrial applications for the technology—not individual ones. The agency notes that it has already “begun to receive submissions using additive manufacturing for both traditional and patient-matched devices,” and says it sees “many more on the horizon.”

Among FDA’s chief concerns, it said, are process verification and validation, which are both key parts of the medical device quality manufacturing regulations.

But the notice also indicates that existing guidance documents, such as those specific to medical device types, will still be in effect regardless of the 3D printing guidance.

Discussion Points

FDA’s proposed list of discussion topics include:

  • Preprinting considerations, including but not limited to:
    • material chemistry
    • physical properties
    • recyclability
    • part reproducibility
    • process validation
  • Printing considerations, including but not limited to:
    • printing process characterization
    • software used in the process
    • post-processing steps (hot isostatic pressing, curing)
    • additional machining
  • Post-printing considerations, including but not limited to:
    • cleaning/excess material removal
    • effect of complexity on sterilization and biocompatibility
    • final device mechanics
    • design envelope
    • verification

– See more at: http://www.raps.org/regulatory-focus/news/2014/05/19000/FDA-3D-Printing-Guidance-and-Meeting/#sthash.cDg4Utln.dpuf


FDA examining regulations for 3‑D printed medical devices


Renee Eaton Monday, October 27, 2014

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The official purpose of a recent FDA-sponsored workshop was “to provide a forum for FDA, medical device manufacturers, additive manufacturing companies and academia to discuss technical challenges and solutions of 3-D printing.” The FDA wants “input to help it determine technical assessments that should be considered for additively manufactured devices to provide a transparent evaluation process for future submissions.”

Simply put, the FDA is trying to stay current with advanced manufacturing technologies that are revolutionizing patient care and, in some cases, democratizing its availability. When a next-door neighbor can print a medical device in his or her basement, it clearly has many positive and negative implications that need to be considered.

Ignoring the regulatory implications for a moment, the presentations at the workshop were fascinating.

STERIS representative Dr. Bill Brodbeck cautioned that the complex designs and materials now being created with additive manufacturing make sterilization practices challenging. For example, how will the manufacturer know if the implant is sterile or if the agent has been adequately removed? Also, some materials and designs cannot tolerate acids, heat or pressure, making sterilization more difficult.

Dr. Thomas Boland from the University of Texas at El Paso shared his team’s work on 3-D-printed tissues. Using inkjet technology, the researchers are evaluating the variables involved in successfully printing skin. Another bio-printing project being undertaken at Wake Forest by Dr. James Yoo involves constructing bladder-shaped prints using bladder cell biopsies and scaffolding.

Dr. Peter Liacouras at Walter Reed discussed his institution’s practice of using 3-D printing to create surgical guides and custom implants. In another biomedical project, work done at Children’s National Hospital by Drs. Axel Krieger and Laura Olivieri involves the physicians using printed cardiac models to “inform clinical decisions,” i.e. evaluate conditions, plan surgeries and reduce operating time.

As interesting as the presentations were, the subsequent discussions were arguably more important. In an attempt to identify and address all significant impacts of additive manufacturing on medical device production, the subject was organized into preprinting (input), printing (process) and post-printing (output) considerations. Panelists and other stakeholders shared their concerns and viewpoints on each topic in an attempt to inform and persuade FDA decision-makers.

An interesting (but expected) outcome was the relative positions of the various stakeholders. Well-established and large manufacturers proposed validation procedures: material testing, process operating guidelines, quality control, traceability programs, etc. Independent makers argued that this approach would impede, if not eliminate, their ability to provide low-cost prosthetic devices.

Comparing practices to the highly regulated food industry, one can understand and accept the need to adopt similar measures for some additively manufactured medical devices. An implant is going into someone’s body, so the manufacturer needs to evaluate and assure the quality of raw materials, processing procedures and finished product.

But, as in the food industry, this means the producer needs to know the composition of materials. Suppliers cannot hide behind proprietary formulations. If manufacturers are expected to certify that a device is safe, they need to know what ingredients are in the materials they are using.

Many in the industry are also lobbying the FDA to agree that manufacturers should be expected to certify the components and not the additive manufacturing process itself. They argue that what matters is whether the device is safe, not what process was used to make it.

Another distinction should be the product’s risk level. Devices should continue to be classified as I, II or III and that classification, not the process used, should determine its level of regulation.

If you are interested in submitting comments to the FDA on this topic, post them by Nov. 10.

FDA Guidance Summary on 3D BioPrinting

fdaregulationguidelinesfor3dbioprinting_1 fdaregulationguidelinesfor3dbioprinting_2 fdaregulationguidelinesfor3dbioprinting_3 fdaregulationguidelinesfor3dbioprinting_4 fdaregulationguidelinesfor3dbioprinting_5 fdaregulationguidelinesfor3dbioprinting_6 fdaregulationguidelinesfor3dbioprinting_7 fdaregulationguidelinesfor3dbioprinting_8 fdaregulationguidelinesfor3dbioprinting_9 fdaregulationguidelinesfor3dbioprinting_10 fdaregulationguidelinesfor3dbioprinting_11






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Bio-inks and 3D BioPrinting

Curator: Stephen J. Williams, Ph.D.


Bio-ink is a material made from living cells that behaves much like a liquid, allowing people to “print” it in order to create a desired shape. This material was developed by researchers at the University of Missouri, Columbia, with the goal of someday being able to do things like print replacements for failing organs. This technology is only in the very early stages of testing and development, but it shows promise.

To make bio-ink, scientists create a slurry of cells that can be loaded into a cartridge and inserted into a specially designed printer, along with another cartridge containing a gel known as bio-paper. After inputting the standards for the thing they want to print, the researchers trigger the printer, and the cartridges alternate layers to build a three dimensional structure, with the bio-paper creating a supportive matrix that the ink can thrive on.

Through a process that is not yet totally understood, the individual droplets fuse together, eventually latticing upwards through the bio-paper to create a solid structure. Understanding this process and the point at which cells differentiate to accomplish different tasks is an important part of creating a usable material; perhaps someday hospitals will be able to use it to generate tissue and organs for use by their patients.


The most obvious potential use for bio-ink is in skin grafting. With this technology, labs could quickly create sheets of skin for burn victims and other people who might be in need of grafts. By creating grafts derived from the patient’s own cells, it could reduce the risk of rejection and scarring. Bio-ink could also be used to make replacements for vascular material removed during surgeries, allowing people to receive new veins and arteries.

Eventually, entire organs could be constructed from this material. Since organs are in short supply around the world, bio-ink could potentially save untold numbers of lives, as patients would no longer have to wait on the transplant list for new organs. The use of such organs could also allay fears about contaminated organ supplies or unscrupulous organ acquisition methods.



Universal Matrix for 3D Tissue Printing

BioInkTM is a chemically-defined hydrogel to support growth of different cell types. It allows cell adhesion, mimics the natural extracellular matrix and is biodegradable.

BioInkTM is provided as a ready-to-use chemically-defined hydrogel to print 3D tissue models. Exclusively designed for regenHU’s BioFactory® and 3DDiscovery® tissue and bio-printers.

A versatile, chemically-defined hydrogel, supporting cell attachment, growth, differentiation and migration. The BioInkTM is suitable for long-term tissue cultivation (in vitro human dermis for up to 7 weeks).








A versatile bioink for three-dimensional printing of cellular scaffolds based on thermally and photo-triggered tandem gelation

  • a Cartilage Engineering + Regeneration Laboratory, ETH Zürich, Otto-Stern-Weg 7, 8093 Zürich, Switzerland
  • b Biomaterials Department, INNOVENT e.V. Jena, Prüssingstrasse 27 B, 07745 Jena, Germany
  • c AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos Platz, Switzerland


Layer-by-layer bioprinting is a logical choice for the fabrication of stratified tissues like articular cartilage. Printing of viable organ replacements, however, is dependent on bioinks with appropriate rheological and cytocompatible properties. In cartilage engineering, photocrosslinkable glycosaminoglycan-based hydrogels are chondrogenic, but alone have generally poor printing properties. By blending the thermoresponsive polymer poly(N-isopropylacrylamide) grafted hyaluronan (HA-pNIPAAM) with methacrylated hyaluronan (HAMA), high-resolution scaffolds with good viability were printed. HA-pNIPAAM provided fast gelation and immediate post-printing structural fidelity, while HAMA ensured long-term mechanical stability upon photocrosslinking. The bioink was evaluated for rheological properties, swelling behavior, printability and biocompatibility of encapsulated bovine chondrocytes. Elution of HA-pNIPAAM from the scaffold was necessary to obtain good viability. HA-pNIPAAM can therefore be used to support extrusion of a range of biopolymers which undergo tandem gelation, thereby facilitating the printing of cell-laden, stratified cartilage constructs with zonally varying composition and stiffness.

bioink presentation_1 bioink presentation_2 bioink presentation_3 bioink presentation_4 bioink presentation_5 bioink presentation_6 bioink presentation_7 bioink presentation_8 bioink presentation_9 bioink presentation_10 bioink presentation_11 bioink presentation_12 bioink presentation_13 bioink presentation_14 bioink presentation_15



For more information see:



And for more information on biopaper and methodology please see this pdf file courtesy of The First Symposium on BioPrinting in Tissue Engineering (see file) biopaper presentation



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Lab Grown Brains and more from Twittersphere on 3D Bio-Printing News

Curator: Stephen J. Williams, Ph.D

How Tiny Lab-Grown Human Brains Are Giving Big Insights Into Autism and more from the Twittershpere




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3-D Printed Liver

Larry H. Bernstein, MD, FCAP, Curator



This is an interesting topic.  We already have liver transplantation.  When the procedure was introduced, a liver transplant could deplete the blood supply in a small state.  Kidney transplantation did not pose that problem, and we are now much beyond classic dialysis with intraperitoneal dialysis at home on a daily basis.   Liver transplantation raises issues about who receives the benefit.  Alcoholism is self destructive, but undoubtedly they are among the recipients.  Hepatocarcinoma is uncommon, and it has a poor prognosis.  Patients who have a transthyretin gene mutant associated with neurodegeneration who are likely to have a family history descending from Portugal, Sweden, Brazil, and a locality in Japan are receiving liver transplants.  The 3-D bioprint model would clearly apply. It becomes of great interest in those who have received blood transfusions or have become infected with HCV.


3D Printed Liver Models Save Lives at Cleveland Clinic

Currently, 3D printing models of patients’ organs is becoming a pretty common and easy practice that is being used in an increasing variety of surgeries. At the time, however, it was still very experimental and required a lot of testing.

“We went through a process for every patient who underwent liver surgery where we resected a portion of the liver, took it out, [and] prior to surgery, we prepared a 3D printed version of it,” said Dr. Zein

Dr. Zein believes that the 2012 trials resulted in the first-ever 3D printed liver. At that time, it took six weeks to print, which seems incredible when you consider how fast 3D printers are today, only three years later. Now, the hospital can print a replica liver in less than 48 hours. As 3D printing technology has improved, so have the models the hospital is able to print. The early models were yellowish and hazy, but now they are as clear as glass, enabling doctors to easily see blood vessels and bile ducts. In 2014, the hospital was using the models regularly during surgeries, and they’ve continued to improve. Different components can be printed individually, removed from the model for closer examination, and then replaced within the larger organ model using a series of magnets. At this point, Zein has printed over 20 liver models.

Having perfected the method of 3D liver modeling, the clinic was able to offer hope to a patient with a liver tumor who had already been turned down by other hospitals. Dr. Zein is thrilled with the possibilities that 3D printing offers for saving lives that could not have been saved before.

“My career has been as a clinical investigator so medical research and investigation is part of my life and it’s probably the most exciting part of my life,” he said. “So I’m very proud of what we did. What comes out of it, in the end, I’m not sure, but I have a feeling that there will be a role for these technologies, 3D printing, in complex surgeries.”


Researchers 3D Print Artificial Liver-like Device to Detoxify The Blood

Nanoengineers at the University of California, San Diego have been taking a different approach to creating a liver, an artificial one. They have been successful in creating a device which functions in a similar manner as the human organ, but is designed to be used outside the body, sort of like dialysis.

Recently engineers have used nanoparticles, tiny particles which are between 1 and 100 nanometers in size, to neutralize pore-forming toxins in the blood. These toxins can either be released by bacteria during an infection, or by insect or snake venom after a bite or sting. The toxins are released into the bloodstream, causing illness, or even death by destroying cells.  They do this by basically poking holes in the cell membranes. The method developed to neutralize the toxins has been heralded as a success, however there is a major risk of secondary poisoning, which can come about when the nanoparticles enter the liver and accumulate.




A team of researchers, led by nanoengineering professor Shaochen Chen, have come up with a solution. Their solution is a matrix, which they 3D print out of a hydrogel material. This matrix is used to house the nanoparticles, and neutralize any pore-forming toxins. This mimicks the functions of the human liver.

“The concept of using 3D printing to encapsulate functional nanoparticles in a biocompatible hydrogel is novel,” said Chen. “This will inspire many new designs for detoxification techniques since 3D printing allows user-specific or site-specific manufacturing of highly functional products.”

The bioprinting technology used by Chen and his team is called, dynamic optical projection stereolithography. Similar to the stereolithography technology used within the resin based 3D printer you may have at home, Chen’s printers use a liquid solution which contains cells as well as a photosensitive biopolymer. It then directs light towards the solution, which solidifies. Layer by layer, the printer gradually builds up the material until they have a finished structure. Chen has been developing this technology thanks to a grant of $1.5 million from the National Institute of Health.  Ultimately this technology could be used in a variety of important applications, producing various medical implants, devices, and human tissues.  Discuss this story at the forum thread at 3DPB.com related to Chen’s 3D printed liver-like device.


Professor Shaochen Chen

Professor Shaochen Chen




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FDA Guidance On Source Animal, Product, Preclinical and Clinical Issues Concerning the Use of Xenotranspantation Products in Humans – Implications for 3D BioPrinting of Regenerative Tissue

Reporter: Stephen J. Williams, Ph.D.


The FDA has submitted Final Guidance on use xeno-transplanted animal tissue, products, and cells into human and their use in medical procedures. Although the draft guidance was to expand on previous guidelines to prevent the introduction, transmission, and spread of communicable diseases, this updated draft may have implications for use of such tissue in the emerging medical 3D printing field.

This document is to provide guidance on the production, testing and evaluation of products intended for use in xenotransplantation. The guidance includes scientific questions that should be addressed by sponsors during protocol development and during the preparation of submissions to the Food and Drug Administration (FDA), e.g., Investigational New Drug Application (IND) and Biologics License Application (BLA). This guidance document finalizes the draft guidance of the same title dated February 2001.

For the purpose of this document, xenotransplantation refers to any procedure that involves the transplantation, implantation, or infusion into a human recipient of either (a) live cells, tissues, or organs from a nonhuman animal source, or (b) human body fluids, cells, tissues or organs that have had ex vivo contact with live nonhuman animal cells, tissues or organs. For the purpose of this document, xenotransplantation products include live cells, tissues or organs used in xenotransplantation. (See Definitions in section I.C.)

This document presents issues that should be considered in addressing the safety of viable materials obtained from animal sources and intended for clinical use in humans. The potential threat to both human and animal welfare from zoonotic or other infectious agents warrants careful characterization of animal sources of cells, tissues, and organs. This document addresses issues such as the characterization of source animals, source animal husbandry practices, characterization of xenotransplantation products, considerations for the xenotransplantation product manufacturing facility, appropriate preclinical models for xenotransplantation protocols, and monitoring of recipients of xenotransplantation products. This document recommends specific practices intended to prevent the introduction and spread of infectious agents of animal origin into the human population. FDA expects that new methods proposed by sponsors to address specific issues will be scientifically rigorous and that sufficient data will be presented to justify their use.

Examples of procedures involving xenotransplantation products include:

  • transplantation of xenogeneic hearts, kidneys, or pancreatic tissue to treat organ failure,
  • implantation of neural cells to ameliorate neurological degenerative diseases,
  • administration of human cells previously cultured ex vivo with live nonhuman animal antigen-presenting or feeder cells, and
  • extracorporeal perfusion of a patient’s blood or blood component perfused through an intact animal organ or isolated cells contained in a device to treat liver failure.

The guidance addresses issues such as:

  1. Clinical Protocol Review
  2. Xenotransplantation Site
  3. Criteria for Patient Selection
  4. Risk/Benefit Assessment
  5. Screening for Infectious Agents
  6. Patient Follow-up
  7. Archiving of Patient Plasma and Tissue Specimens
  8. Health Records and Data Management
  9. Informed Consent
  10. Responsibility of the Sponsor in Informing the Patient of New Scientific Information

A full copy of the PDF can be found below for reference:


An example of the need for this guidance in conjunction with 3D printing technology can be understood from the below article (source http://www.geneticliteracyproject.org/2015/09/03/pig-us-xenotransplantation-new-age-chimeric-organs/)

Pig in us: Xenotransplantation and new age of chimeric organs

David Warmflash | September 3, 2015 | Genetic Literacy Project

Imagine stripping out the failing components of an old car — the engine, transmission, exhaust system and all of those parts — leaving just the old body and other structural elements. Replace those old mechanical parts with a brand new electric, hydrogen powered, biofuel, nuclear or whatever kind of engine you want and now you have a brand new car. It has an old frame, but that’s okay. The frame wasn’t causing the problem, and it can live on for years, undamaged.

When challenged to design internal organs, tissue engineers are taking a similar approach, particularly with the most complex organs, like the heart, liver and kidneys. These organs have three dimensional structures that are elaborate, not just at the gross anatomic level, but in microscopic anatomy too. Some day, their complex connective tissue scaffolding, the stroma, might be synthesized from the needed collagen proteins with advanced 3-D printing. But biomedical engineering is not there yet, so right now the best candidate for organ scaffolding comes from one of humanity’s favorite farm animals: the pig.

Chimera alarmists connecting with anti-biotechnology movements might cringe at the thought of building new human organs starting with pig tissue, but if you’re using only the organ scaffolding and building a working organ from there, pig organs may actually be more desirable than those donated by humans.

How big is the anti-chimerite movement?

Unlike anti-GMO and anti-vaccination activists, there really aren’t too many anti-chemerites around. Nevertheless, there is a presence on the web of people who express concern about mixing of humans and non-human animals. Presently, much of their concern is focussed on the growing of human organs inside non-human animals, pigs included. One anti-chemerite has written that it could be a problem for the following reason:

Once a human organ is grown inside a pig, that pig is no longer fully a pig. And without a doubt, that organ will no longer be a fully human organ after it is grown inside the pig. Those receiving those organs will be allowing human-animal hybrid organs to be implanted into them. Most people would be absolutely shocked to learn some of the things that are currently being done in the name of science.

The blog goes on to express alarm about the use of human genes in rice and from there morphs into an off the shelf garden variety anti-GMO tirade, though with an an anti-chemeric current running through it. The concern about making pigs a little bit human and humans a little bit pig becomes a concern about making rice a little bit human. But the concern about fusing tissues and genes of humans and other species does not fit with the trend in modern medicine.

Utilization of pig tissue enters a new age 


A porcine human ear for xenotransplantation. source: The Scientist

For decades, pig, bovine and other non-human tissues have been used in medicine. People are walking around with pig and cow heart valves. Diabetics used to get a lot of insulin from pigs and cows, although today, thanks to genetic engineering, they’re getting human insulin produced by microorganisms modified genetically to make human insulin, which is safer and more effective.

When it comes to building new organs from old ones, however, pig organs could actually be superior for a couple of reasons. For one thing, there’s no availability problem with pigs. Their hearts and other organs also have all of the crucial components of the extracellular matrix that makes up an organ’s scaffolding. But unlike human organs, the pig organs don’t tend to carry or transfer human diseases. That is a major advantage that makes them ideal starting material. Plus there is another advantage: typically, the hearts of human cadavers are damaged, either because heart disease is what killed the human owner or because resuscitation efforts aimed at restarting the heart of a dying person using electrical jolts and powerful drugs.

Rebuilding an old organ into a new one

How then does the process work? Whether starting with a donated human or pig organ, there are several possible methods. But what they all have in common is that only the scaffolding of the original organ is retained. Just like the engine and transmission of the old car, the working tissue is removed, usually using detergents. One promising technique that has been applied to engineer new hearts is being tested by researchers at the University of Pittsburgh. Detergents pumped into the aorta attached to a donated heart (donated by a human cadaver, or pig or cow). The pressure keeps the aortic valve closed, so the detergents to into the coronary arteries and through the myocardial (heart muscle) and endocardial (lining over the muscle inside the heart chambers) tissue, which thus gets dissolved over the course of days. What’s left is just the stroma tissue, forming a scaffold. But that scaffold has signaling factors that enable embryonic stem cells, or specially programed adult pleuripotent cells to become all of the needed cells for a new heart.

Eventually, 3-D printing technology may reach the point when no donated scaffolding is needed, but that’s not the case quite yet, plus with a pig scaffolding all of the needed signaling factors are there and they work just as well as those in a human heart scaffold. All of this can lead to a scenario, possibly very soon, in which organs are made using off-the-self scaffolding from pig organs, ready to produce a custom-made heart using stem or other cells donated by new organ’s recipient.

David Warmflash is an astrobiologist, physician, and science writer. Follow @CosmicEvolution to read what he is saying on Twitter.

And a Great Article in The Scientist by Dr. Ed Yong Entitled

Replacement Parts

To cope with a growing shortage of hearts, livers, and lungs suitable for transplant, some scientists are genetically engineering pigs, while others are growing organs in the lab.

By Ed Yong | August 1, 2012

Source: http://www.the-scientist.com/?articles.view/articleNo/32409/title/Replacement-Parts/

.. where Joseph Vacanti and David Cooper figured that using

“engineered pigs without the a-1,3-galactosyltransferase gene that produces the a-gal residues. In addition, the pigs carry human cell-membrane proteins such as CD55 and CD46 that prevent the host’s complement system from assembling and attacking the foreign cells”

thereby limiting rejection of the xenotransplated tissue.

In addition to issues related to animal virus transmission the issue of optimal scaffolds for organs as well as the advantages which 3D Printing would have in mass production of organs is discussed:

To Vacanti, artificial scaffolds are the future of organ engineering, and the only way in which organs for transplantation could be mass-produced. “You should be able to make them on demand, with low-cost materials and manufacturing technologies,” he says. That is relatively simple for organs like tracheas or bladders, which are just hollow tubes or sacs. Even though it is far more difficult for the lung or liver, which have complicated structures, Vacanti thinks it will be possible to simulate their architecture with computer models, and fabricate them with modern printing technology. (See “3-D Printing,” The Scientist, July 2012.) “They obey very ordered rules, so you can reduce it down to a series of algorithms, which can help you design them,” he says. But Taylor says that even if the architecture is correct, the scaffold would still need to contain the right surface molecules to guide the growth of any added cells. “It seems a bit of an overkill when nature has already done the work for us,” she says.

Other articles of FDA Guidance and 3D Bio Printing on this Open Access Journal Include:

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3-D Medical BioPrinting Overview

Curator: Larry H. Bernstein, MD, FCAP



Osteo3D Opens Marketplace for 3D Printable Medical Models from Real Patient Data   

 BY ON FRI, JULY 24, 2015


There are many companies dedicated to improving the use of 3D printing in the medical sector, and one of them Osteo3D, just released an amazing online repository of medical 3D models. Of course, patient information is private, so some of the “live models” have been made anonymous.  But there are now over 100 3D models available to doctors and other registered medical professionals online, which allows them t0 compare their own patient’s 3D files with Osteo3D models.  In fact, they can 3D print these models at home or wherever they have access to a 3D printer.

But, if a doctor or medical student doesn’t have a 3D printer, they can order a print directly from Osteo3D.  The online platform is powered by cloud printing site df3d and is meant to increase awareness of the usefulness of 3D printing among healthcare professionals.  Osteo3D hopes that, by collaborating with healthcare professionals, the tech industry, and academic institutions, they will help facilitate access and lower costs for the use of 3D printing in the healthcare field.

Currently the models are divided into the following categories:

  • Head and neck
  • Spine
  • Chest
  • Abdomen and pelvis
  • Extremities

When you click on 3D view, you don’t get quite the same level of control and depth asSketchfab, and some of the models look like pixels are growing out of them, but I didn’t pay to download any of the models, so I can’t say for sure. They are currently on the lookout for 3D printing partners who can help them deliver these 3D prints from their cloud platform to their customers around the world.





We’ve covered a number of stories that revolve around the combination of scanning/sensing technologies, great 3D modeling software, and 3D printing.  This combination has arguably had the most impact on the quality of human life as it is seen in the medical sector.  Diagnoses are made to a patient with a life-threatening condition.  Doctors, then, use 3D scanning technology to capture the reality data of a patient’s affected area, whether it be an organ, vasculature, bone structure, or combination of all three.  Next, a 3D model is created and manipulated using innovative software, and the model is 3D printed.  Surgery is practiced and visualized on the model, and then performed on the patient.  After doctors have all of this information, they use it to teach other doctors and nurse practitioners.  So, why not spread this wealth of information?  This is digital information, after all.  Any 3D model that is successfully used to print a 3D model of a diagnosed patient can be transferred anywhere, to anyone.

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Biofabrication with Stem Cells

Curator: Larry H. Bernstein, MD, FCAP



Biofabrication  Special Issue:  Dec 2015; 7(4).    http://iopscience.iop.org/1758-5090/7/4


Three-dimensional bioprinting of embryonic stem cells directs highly uniform embryoid body formation

Liliang Ouyang1,2,6, Rui Yao1,2,6, Shuangshuang Mao1,2, Xi Chen3, Jie Na3 and Wei Sun1,2,4,5
Biofabrication, Volume 7(4)    http://iopscience.iop.org/article/10.1088/1758-5090/7/4/044101/meta

With the ability to manipulate cells temporarily and spatially into three-dimensional (3D) tissue-like construct, 3D bioprinting technology was used in many studies to facilitate the recreation of complex cell niche and/or to better understand the regulation of stem cell proliferation and differentiation by cellular microenvironment factors. Embryonic stem cells (ESCs) have the capacity to differentiate into any specialized cell type of the animal body, generally via the formation of embryoid body (EB), which mimics the early stages of embryogenesis. In this study, extrusion-based 3D bioprinting technology was utilized for biofabricating ESCs into 3D cell-laden construct. The influence of 3D printing parameters on ESC viability, proliferation, maintenance of pluripotency and the rule of EB formation was systematically studied in this work. Results demonstrated that ESCs were successfully printed with hydrogel into 3D macroporous construct. Upon process optimization, about 90% ESCs remained alive after the process of bioprinting and cell-laden construct formation. ESCs continued proliferating into spheroid EBs in the hydrogel construct, while retaining the protein expression and gene expression of pluripotent markers, like octamer binding transcription factor 4, stage specific embryonic antigen 1 and Nanog. In this novel technology, EBs were formed through cell proliferation instead of aggregation, and the quantity of EBs was tuned by the initial cell density in the 3D bioprinting process. This study introduces the 3D bioprinting of ESCs into a 3D cell-laden hydrogel construct for the first time and showed the production of uniform, pluripotent, high-throughput and size-controllable EBs, which indicated strong potential in ESC large scale expansion, stem cell regulation and fabrication of tissue-like structure and drug screening studies.

With the capability of self-renewal and differentiating into all somatic cell types, embryonic stem cells (ESCs) hold great promise as an in vitro model system for studies in early embryonic development, as well as a robust cell source for applications in diagnostics, therapeutics, and drug screening [1]. Derived from the inner cell mass of a blastocyst, ESCs requires delicate culture condition and trend to cluster together, and in particular, forms three-dimensional (3D) cellular spheroids termed embryoid body (EB) [2]. In order to better understand stem cell niche and regulation of ESC differentiation and reprogramming, in vitro recapitulation of the spatial distribution of cells, cell–cell and cell–matrix interactions, is of paramount importance [35]. Compared with 2D monolayer culture, 3D cell culture is believed to confer a higher degree of clinical and biological relevance to in vitro model [6, 7], since the spatial arrangement of cells and extra-cellular matrix could influence cell differentiation and function both in vivo [8] and in vitro[9]. Therefore, reconstruction of 3D cell microenvironment is critical to directing stem cell fate and generating cell sources for tissue engineering, regenerative medicine and drug screening studies.

By mimicking some of the spatial and temporal aspects of in vivo development, EB is a basic 3D model for ESCs culture and differentiation studies. It was reported that the size and uniformity of EBs could vastly influence stem cell fate [1012]. Various methods have been used to fabricate such cellular spheroid, basically including static suspension, hanging-drop and multiwell culture, most of which doesn’t involve biomaterials. Static suspension method inoculate suspension of ESCs onto non-adhesive plate to allow cells spontaneously aggregate into spheroid. This method is easy to operate, but showed limited control over the EBs size and shape due to the probability that ESCs encounter each other accidentally [13]. Hanging-drop is a common method to produce size-controlled homogeneous EBs, where droplets of ESCs suspension are pipetted onto the lid of a Petri dish and EBs was generate by gravity after overturning the dish [14]. However, manual pipetting is labor intensive and the reproducibility varies with operators. Multiwell culture offers high-throughput solution for EB formation through cell aggregation in uniformly shaped microwell arrays but requires expensive microwell culture plates [10, 15]. Besides, there are few customized microwell culture plates available in the market.

Recent advances in bioprinting technologies facilitated the precise deposition of ESCs in a reproducible manner. Xu et al [16] and Shu et al [17] printed ESCs suspension solution into 2D patterns as hanging-drop approach for EB formation, without the cell-biomaterial interaction. Corr and Xie [18, 19] applied laser direct-write method in bioprinting of mouse ESCs together with gelatin. ESCs maintained the pluripotency while proliferation and formed EB. EB size can be controlled by cell density and colony size. However, these studies just generated 2D cellular array without 3D cell–matrix interactions, and cell–cell interaction happens within one drop but not among different drops. To better recapitulate the characteristics of in vivo cell microenvironment, 3D customized cell/matrix construct with macro-porous structure might be a preferred choice. To our knowledge, there has been no report about bioprinting of ESCs into 3D cell-laden constructs.

The extrusion-based temperature-sensitive 3D bioprinting technology was developed in our lab and has been utilized for bioprinting of hepatocytes [20], adipose tissue-derived stem cells (ADSCs) [21], C2C12 cells [22], hela cells [23] and 293FT cells [24]. Most commonly used biomaterials for this technology are gelatin and alginate. Gelatin, a type of denatured collagen, is widely used as a coating for feeder layer-free mouse ES cell culture. Alginate, extracted from brown algae, is proving to have a wide applicability in tissue engineering and drug delivery and also used in embedding mouse ESCs for EB formation [25]. It has been proved in many studies that encapsulation of ESCs in hydrogels would direct EB formation with the maintenance of pluripotency [2628]. Hence, we hypothesized that the bioprinting of 3D ESC-laden construct would maintain the stem cell pluripotency and address the challenges associated with the current methods for EB formation.

In this study, we investigated the feasibility of applying extrusion-based temperature-sensitive 3D bioprinting technology in bioprinting of ESCs with hydrogels into 3D macro-porous structure, with the maintenance of viability, pluripotency, cell growth and to direct EB formation. Printing process parameters were optimized to obtain a high cell survival rate (90%) after printing process and construct formation. Stem cell pluripotency was examined by the expression of stem cell markers (octamer binding transcription factor 4 (Oct4), stage specific embryonic antigen 1 (SSEA1) and a homeodomain-bearing transcriptional factor (Nanog)) and the ability to form EBs. The regulation of EB formation in the 3D bioprinted construct was systematically compared with commonly used methodology, where EB formation relies on cell aggregating as well as cell proliferation. Results demonstrated that this novel technology generated pluripotent, high-throughput, highly uniform and size controllable EBs under static culture condition without complex equipment. This study established the feasibility of fabricating 3D in vitro tissue-like model using ESCs for the first time, creating engineered microenvironment for pluripotent stem cells with the ability of placing cells and materials spatially in a reproducible manner.



3.1. 3D bioprinting and cell viability optimization

In this study, many process parameters, e.g. nozzle inner diameter, nozzle insulation temperature and chamber temperature were examined to optimize cell viability after 3D construct fabrication. It was demonstrated that larger nozzle diameter resulted in higher cell viability (figure 2(A)). Specially, the cell viability under Nozzle-160 μm (81.59% ± 1.74%) was lower than those under Nozzle-260 μm (88.06% ± 1.98%), Nozzle-410 μm (89.59% ± 0.71%) and Nozzle-510 μm (90.84% ± 1.02%), with significant differences. Nozzle diameter of 260 μm, 410 μm and 510 μm showed no significant differences in terms of cell viability.

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Figure 2. The influence of bioprinting parameters on ESC viability is determined by fluorescence live/dead staining. (A) The influence of printing nozzle inner diameter on ESC viability (Insu-30 °C and Cham-10 °C). (B) The influence of nozzle insulation temperature and chamber temperature on ESC viability. Insu-25 °C means keeping the nozzle insulation temperature at 25 °C. Cham-4 °C means setting the chamber temperature at 4 °C, and so as others. (C) The fluorescent staining images show the live (green) and dead (red) cells at different days during culture period. Scale bar: 100 μm.

Insulation and chamber temperatures were altered to study their influences on cell viability (figure 2(B)). As a positive control, ESCs/hydrogel mixture without bioprinting were stained with fluorescence live/dead reagent, and showed 93.14% ± 1.31% cell viability. When insulation temperature was set at 25 °C (labeled as ‘Insu-25 °C’), cell viability increased with the chamber temperature from 55.52% ± 2.37% under 4 °C (labeled as ‘Cham-4 °C’) to 78.22% ± 2.55% under 10 °C (labeled as ‘Cham-10 °C’) with significant differences. When the insulation temperature was set at 30 °C (labeled as ‘Insu-30 °C’), nearly 90% ESCs remained alive under the chamber temperature of 7 °C and 10 °C (labeled as ‘Cham-7 °C’ and ‘Cham-10 °C’), significantly more than that under Cham-4 °C (72.40% ± 2.46%). To achieve both high ESC viability and a clear construct configuration, the process parameter combination of Nozzle-260 μm, Cham-10 °C and Insu-30 °C was chosen.

After culturing for three days, few cells were found dead, which were isolated from living EBs (figure 2(C)). On day 5 and day 7, a few dead cells were observed on the edge of EBs. About 5% ESCs were stained dead on day 7. As the static culturing continued, 9.69% ± 1.77%, 17.72% ± 2.91% and 40.64% ± 2.06% were found dead on day 8, day 9 and day 10, respectively (supplement 2). So, we chose 7 days as the culture period in the following analysis.

3.2. Construct structural stability and EB formation

A 3D cellular construct with the cross section of 8 mm × 8 mm and height of 1 mm was fabricated under the optimized process parameter. The 3D construct demonstrated macro-porous grid structure in which the hydrogel threads were evenly distributed according to the computer design (figure 3(A)). Both the width of the threads and the gap between the threads were homogeneous, that is 728.2 μm ± 24.9 μm and 424.3 μm ± 17.8 μm, respectively, suggesting 3D cellular construct formation in a highly controlled manner. ESCs were embedded uniformly in the hydrogel matrix threads, developing a specific 3D microenvironment.

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Figure 3. Images of the printed cellular model with grid structure. (A) Full view of the cellular construct. (B) Phase-contrast images demonstrating the cell morphology and distribution of different cell density at day 3, day 5 and day 7. Scale bar: 1 mm.

During the culture period, ESCs tended to grow as spheroid cellular aggregates, also known as EB. The cell density in the 3D hydrogel construct were determined by the initial cell density in the ESC/alginate/gelatin mixture and showed significant influence on the yield and density of EBs formed in the construct (figure 3(B)). It was demonstrated by semi-quantitative analysis of figure 3(B) that, the percentage of area occupied by EBs varied from 52% to 85% when initial cell density changed from 0.5 mln mL−1 to 2.0 mln mL−1 . Most of the EBs were contained in the hydrogel threads in the culturing period. However, when the initial cell density was as high as 2.0 mln ml−1, some of the EBs were observed running off from the threads into the throughout holes.

3.3. Cell proliferation

ESCs formed spheroid EBs in the 3D hydrogel construct and the diameter of the EBs enlarged with culturing time while keeping their spatial location in the hydrogel thread, indicating EB formation by ESC proliferation rather than aggregation (figure 4(A)). Compared with traditional 2D culture, ESCs showed different proliferation rate indicated by the OD value measure by CCK-8 kit (figure 4(B)). The normalized OD value of the 3D in situ group grew faster than that of 2D from day 1 to day 3, while slowing down after day 3 and being much less than that of 2D at day 7. However, 3D harvest group showed a generally faster growth rate than 2D during the one week culturing, with a significant difference. In addition, the diameter of EB was also measured to indicate ESC proliferation rate. When comparing the normalized EB volume with normalized 2D OD value, 3D samples also maintained a significantly faster growth rate than 2D, though the EB volume had huge variance (figure 4(B)).

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Figure 4. EB growing and cell proliferation. (A) Magnified images of the same location in 3D printed cellular construct at different times. (B) ESC proliferation in the 3D construct compared with 2D culture. All the date were normalized to the value of day 1. Scale bar: 200 μm.

Pluripotency markers, i.e. Oct4, SSEA1 and Nanog were analyzed to determine the pluripotency maintenance of ESCs after 7 day culture in the 3D hydrogel construct. Immunofluorescence staining and flow cytometry analysis showed that almost all of the cells within the EB were successfully stained both Oct4 and SSEA1. Because of the limitation of confocal capacity when dealing with large scale aggregates, the central part of the EB was darker than the edge (figure5(A)). Flow cytometry analysis demonstrated that 97.2% and 99.0% cells were positively stained with Oct4 and SSEA1 respectively (figure 5(B)). The qRT-PCR results demonstrated that the gene expression level of Oct4 and Nanog in our 3D samples were close to those in 2D (within the deviation of ±3%), without significant difference, confirming that cells have maintained pluripotency (figure 5(C)).

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Figure 5. ESC pluripotency at day 7 was determined by CLSM, flow cytometry and qRT-PCR. (A) Immunofluorescence images of EBs stained with Oct4, SSEA1 and DAPI. (B) Quantification of 3D dissociated cells marked with Oct4 and SSEA1 by using flow cytometry. (C) Gene expression of Oct4 and Nanog in 3D versus 2D by using qRT-PCR. Scale bar: 50 μm.

EBs were harvested from the 3D hydrogel construct at different time intervals to analyze EB morphology (figure 6(A)). Most of the EBs were separated without fusion. The center part of the EBs was darker than edge part, especially at day 5 and day 7, indicating the 3D sphere structure of EBs. Through analyzing the size of 250 random EBs for each sample, the histogram of EB diameter were obtained, showing a Gauss distribution curve (figure 6(B)). The results demonstrated that the EB size increased significantly from about 50 μm to about 110 μm when the construct was cultured from day 3 to day 7 (figure 6(C)). Cell density had little influence on EB average size. However, increased cell density would result in the reduction of the uniformity of EB size, especially at day 7; the EB diameter of 2.0 mln mL−1 group at day 7 was vastly heterogeneous, with a deviation of 42.30 μm, which was much more than those of other two groups.

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Figure 6. EB formation in different cell density: (A) optical images of released EBs at different days. (B) EB diameter and (C) EB circularity distributions at different days. Summary of the (D) diameter and (E) circularity. 250 EBs were applied for diameter and circularity measurements for each group. Scale bar: 200 μm.

Circularity was measured to assess the quality of EBs (figure 6(D)). For the 0.5 mln mL−1 group, most of the EBs were close to a standard spheroid with the circularity centered in 0.9 for the three time points. As to the other two groups, the circularity at day 3 is similar to that of 0.5 mln mL−1group, while the circularity frequency peaks had a significant decrease at day 5 and day 7. In particular, about 20% EBs had a circularity under 0.8 at day 5 and day 7 for the 2.0 mln mL−1group. In general, the circularity decreased with the increase of culture time and initial cell density in the hydrogel (figure 6(E)).

3.6. Comparison with other EB formation methods

Considering this was a novel methodology of EB formation, we systematically compared the commonly used static suspension and hanging drop methods with the 3D bioprinting method for EB formation. As demonstrated by the phase-contrast images (figure 7(A)), EBs generated by static suspension method showed more uncontrollable morphology rather than round spheroid. The distribution of EB diameter clearly demonstrated that 3D bioprinting technology generated EBs with higher uniformity compared with static suspension technology, especially for the larger EB diameter, i.e. 60 ~ 70 μm and 100 ~ 110 μm regions (figure 7(B)). In particular, the EBs with 30 ~ 50 μm diameter presented vastly irregular shape in suspension technology, which was confirmed by the circularity curve (figure 7(C)). On the other hand, EBs generated by 3D bioprinting technology showed higher circularity regardless of the diameter regions, suggesting more regular shape (figure 7(C)). More characteristic like EB forming motivation, size control method, EB diameter range, uniformity, yield, operation complexity were compared among 3D bioprinting technology, static suspension technology and hanging drop technology, as listed in table 1.

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Figure 7. Comparison of static suspension and 3D bioprinting technology for generating EBs. (A) Phase-contrast images showing the morphology of EBs generated by static suspension technology and 3D bioprinting technology. (B) The EB diameter histograms presented the distribution of EB size with a Gauss distribution fitting. (C) The circularity curves contrasted the EB qualities.

Table 1.  Comparison of three EB forming methods.
Hanging-drop Suspension 3D print
Forming mechanism Aggregation by gravity Self-aggregation Proliferation
Size control Time and cell density Time and cell density Mainly time
Diameter range 50 ~ 500 μm 50 ~ 500 μm 30 ~ 200 μm
Uniformity High Low Medium-high
Yield Low High High
Operation Time-consuming for seeding and medium refresh Complex for medium refresh Time-saving and easy for medium refresh


4. Discussion

3D cell culture environment and tissue-like models have drawn great attention because they can be tuned to promote certain levels of cell differentiation and tissue organization, which is difficult in traditional 2D culture systems for their failing to reconstitute the in vivo cellular microenvironment [30, 31]. Various 3D culture systems have been developed to study the cellular behavior affected by spatial and temporal cell–cell and cell–matrix interactions. Among these methods, 3D bioprinting, typically containing jet-, laser- and extrusion-based methods, is a promising technique to manipulate cells/matrix deposition and ultimately generate 3D complex tissues or organs. This technique have been used in printing cells derived from adult, embryonic and even tumor tissues for tissue engineering and drug screening applications. With the capacity to expand unlimitedly in vitro and differentiate into a variety of therapeutic cell types, ESCs have generated great enthusiasm and are being applied in bioprinting studies until recently. As a relatively sensitive cell type, ESCs might suffer greater problems in a printing process compared with other types of cells. Several studies had been conducted to print ESCs, maintaining their viability and pluripotency [1619]. Instead of creating 3D tissue-like constructs, these studies were more likely to generate cellular droplet array with precise control of distribution. Here we described the work of establishing a 3D ESC-laden hydrogel construct using extrusion-based bioprinting technology. The results demonstrated high proliferation rate of pluripotent ESCs in the hydrogel construct, and a versatile technology for generating highly uniform and high throughput EBs.

Cell viability after 3D bioprinting and construct formation was determined when evaluating the limitations of bioprinting ESCs. Cells would be lysed or damaged due to osmotic effects in the solution, heat increase and mechanical stress during printing. In the protocol presented in this work, about 6.86% ± 1.31% cells were dead during the cell/hydrogel solution preparation process before 3D bioprinting (figure 2(B)). We assumed this was caused by cell dissociation process, together with the osmosis and stirring operation of hydrogel materials. In an inkjet printing study, 15% Chinese Hamster Ovary cells were detected dead before printing process [32]. Thermal effects of the ejector reservoir in the inkjet printing process and laser force in laser-based printing would be the cause of cell death, in addition to the impact force when cellular droplets were jetted to a rigid substrate in a very short time. Under a different fabricating strategy, the extrusion-based bioprinter extruded the cell-laden cylinders softly on the substrate and controlled the temperature under 30 °C, without the concerns about the thermal and sharply impacting effects. However, cells would inevitably suffer from shear force when the cell-laden hydrogels were continuously extruded through a limited space in the nozzle. We hypothesized that nozzle size and hydrogel viscosity would influence shear force and hence influence cell viability. The cell viability data of different nozzle sizes, chamber and insulation temperatures supported this hypothesis (figures 3(A) and (B)). In our previous study, more than 90% Hela cells were alive after bioprinting under the parameters of Insu-25 °C/Cham-4 °C and Nozzle-260 μm [23], while the viability of ESCs was only 55.52% ± 2.37% under the same parameter combination. When increasing the insulation and chamber temperature to 30 °C and 10 °C respectively, the viability showed a significant increase to 90%. Taking into the account of cell death before bioprinting, optimized parameters led to only 5% cell death during printing, indicating a broad future applicability of this technique to various cell types ranging from tumor cells to ESCs. Additionally, few dead cells were observed during one-week culture period (figure3(C)). On the other hand, when the culture period was extended to more than 7 days, more and more ESCs suffered from apoptosis and lysis, possibly due to contact inhabitation and insufficient mass transfer to the center of EB with the increasing of EB size. Therefore, 7 days was chose as the experiment time window for this study.

Apart from cell viability, the maintenance of pluripotency is another essential criterion for ESCs regulation and application. The results of immunofluorescence staining and FACS analysis showed a high expression rate (98%) of stem cell pluripotent markers Oct4 and SSEA1 at day 7 (figure 4), indicating that cells remained undifferentiated state during the whole experimental period. Naturally, it can be inferred that the printing process also had little influence on ESC pluripotency.

In the cell-laden hydrogel culture system, both the cell type and matrix material could influence cell growth. Human mesenchymal stem cells remained alive but did not proliferate when encapsulated in alginate [33, 34]. While human ADSCs could proliferated for a short period of time in alginate hydrogel microspheres but showed significantly higher proliferation rate in gelatin/alginate microspheres [35]. As a widely used hydrogel, alginate has the disadvantages of low cell adhesiveness and poor support for cell proliferation [36]. Adding gelatin would improve the cellular adhesive condition and hence favor cell expansion. In this study, the fabricated multilayered constructs offered a 3D microenvironment surrounded by gelatin/alginate materials for ESCs to adhere, self-renew, and cellular spheroid, termed EB, was generated in situ because of cell proliferation. Once EB was formed, the spheroid structure supported expansion of subpopulations with differing proliferation, nutrition and oxygenation status compared with conventional monolayer system. It is reported that the proliferation of mouse ESCs was higher when embedded in fibrin gels versus 2D suspension culture [27]. Similarly, in this study, ESCs in 3D constructs proliferated faster than 2D culture sample when being released from hydrogel to read OD value. This operation was aimed to avoid the influence of interactions between reagent molecular and matrix materials (figure 6 and supplement 3). Additionally, the enlargement of EB diameter, which also reflected ESC proliferation, confirmed this result (figure 6).

Typically stimulated via generation of EBs, ESC differentiation depends on numerous cues throughout the EB environment, including EB size and shape, as well as their uniformities. In general, several characteristics should be concerned for EB formation system, including reproducibility, symmetry, ease of use and scalability [37]. In the traditional EB formation methodology, like suspension and hanging-drop, EBs were created via cell gathering and proliferation. In these methods, it was essential to get a balance between allowing necessary ESC aggregation for EB formation and preventing EB agglomeration for efficient cell growth and differentiation [14]. Static suspension cultures produced a large number of EBs with simple operation, but the size and shape of the resulting EBs were highly uncontrollable and irregular due to the tendency of EBs to agglomerate after initial formation, as shown in figure 7. Hanging-drop method served as a golden tool to generate uniform and reproducible EBs with fully aggregating of cells under gravity and non-agglomeration of EBs in different drops. However, it faced the intrinsic limitation of scalability. The 3D bioprinting method presented in this study addressed some of the problems, producing massively homogeneous EBs with regular shape and controllable shape. In this 3D cell-laden hydrogel system, ESCs were immobilized and restricted to aggregate with each other, and would not agglomerate until they are large enough to connect with each other. When the initial cell density was increased, the average distance between two original EBs was closer and these EBs are more likely to agglomerate with each other while proliferation, which is also one of the concerns when we choose the experiment time period. As a result, the EB uniformity of 2.0 mln mL−1 group was not that good as those of 0.5 mln mL−1 and 1.0 mln mL−1 groups, especially after culturing for one week (figure 6). Without the initial cell aggregating, the size of EBs in our model was mainly determined by the culture time. Also, it would take longer to reach the same scale of EB diameter compared with suspension method, probably due to the physical constrain of the matrix material. For example, it took 5 days and 2 days to get EBs ranging 60 ~ 70 μm for 3D printing and suspension methods, respectively (figure7). Besides, thanks to the interconnected channels design in the 3D construct which allowed mass transfer, EBs could be produced in a large scale by changing the construct volume and cell density. In the six-layer construct with 1.0 million cells per milliliter for example, EBs got a stable yield of about 3000 cm−2, while the EB yield by suspension technology was about 900 cm−2(seeding 0.5 million cells in a 35 mm dish) and no more than 10 EBs [38] could be produced in 1 cm2 area in hanging-drop method, which was also demonstrated by our experiments (supplement 4).

In summary, this study presented the high throughput production of pluripotent, uniform, regular and controllable EBs with the diameter smaller than 150 μm during one week culture. In a gelatin-based laser printing method, EBs with the diameter of about 100 μm were also generated to avoid EB agglomeration in gels [19]. EBs with different size exhibit different gene expression and differentiation fate. Park et al [39] found that 100 μm diameter EBs of mouse ESCs expressed increased ectoderm markers while 500 μm diameter EBs expressed endoderm and mesoderm markers. Furthermore, Messana et al [12] demonstrated that mouse ESCs derived from small EBs (<100 μm) had a greater chondrogenic potential than those from larger EBs. Hwang [10] reported that human endothelial cell differentiation was increased in smaller EBs (150 μm) while cardiogenesis was enhanced in larger EBs (450 μm). However, large EBs might be associated with limited mass transfer and the diffusion of biochemical through EBs is demonstrated to be linked to differentiation of ESCs [40]. While the effect of EB size on differentiation remains to be shown in our model, we hypothesize that EBs with the diameter smaller than 150 μm would mediate specific differentiation trajectory, which will be confirmed in the future work.

Demonstrating the advantages of reproducibility, high throughput, regular shape and controlled size, we believe this is a versatile technology for EB generation. But, this 3D printing system does not serve as an EB formation method solely. The ESC-laden hydrogel 3D construct can be dissolved at a proper time point to harvest massive EBs with desired size for ES cell research. Or, the ESC-laden hydrogel 3D construct can be maintained to perform 3D ESC differentiation studies to explore the regulation of EB size, matrix material and 3D structure on ESC differentiation lineages. Furthermore, this technology hold the potential to serve as a versatile tool for the generation of tissue-like structure and organ/tissue on chip based on controlled ESC differentiation.

5. Conclusion

In this study, we reported successful bioprinting of mouse ESCs with hydrogel into a 3D multilayered construct for the first time. Extrusion-based bioprinting technology was applied. Upon parameter optimization, ESCs demonstrated high viability of 90% after 3D printing and construct formation. Cells continued self-renewal in the construct and exhibited a higher proliferation rate compared with conventional 2D culture. 98% cells expressed the canonical pulripotent markers Oct4 and SSEA1 at day 7, indicating that most of the ESCs remained undifferentiated state after printing and culturing. Large quantities of uniform EBs with regular shape and adjustable size were generated through cell proliferation, while avoiding EBs agglomeration. This work indicated the feasibility of fabricating complex 3D tissue-like model based on pluripotent stem cells for applications in pharmacy, regenerative medicine, stem cell expansion and biology studies.


Bioprinting of human pluripotent stem cells and their directed differentiation into hepatocyte-like cells for the generation of mini-livers in 3D

Alan Faulkner-Jones1,2, Catherine Fyfe3, Dirk-Jan Cornelissen1,2, John Gardner3, Jason King3,4,Aidan Courtney3,4 and Wenmiao Shu1,2

We report the first investigation into the bioprinting of human induced pluripotent stem cells (hiPSCs), their response to a valve-based printing process as well as their post-printing differentiation into hepatocyte-like cells (HLCs). HLCs differentiated from both hiPSCs and human embryonic stem cells (hESCs) sources were bioprinted and examined for the presence of hepatic markers to further validate the compatibility of the valve-based bioprinting process with fragile cell transfer. Examined cells were positive for nuclear factor 4 alpha and were demonstrated to secrete albumin and have morphology that was also found to be similar to that of hepatocytes. Both hESC and hiPSC lines were tested for post-printing viability and pluripotency and were found to have negligible difference in terms of viability and pluripotency between the printed and non-printed cells. hESC-derived HLCs were 3D printed using alginate hydrogel matrix and tested for viability and albumin secretion during the remaining differentiation and were found to be hepatic in nature. 3D printed with 40-layer of HLC-containing alginate structures reached peak albumin secretion at day 21 of the differentiation protocol. This work demonstrates that the valve-based printing process is gentle enough to print human pluripotent stem cells (hPSCs) (both hESCs and hiPSCs) while either maintaining their pluripotency or directing their differentiation into specific lineages. The ability to bioprint hPSCs will pave the way for producing organs or tissues on demand from patient specific cells which could be used for animal-free drug development and personalized medicine.


Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.


New drug development can take 10 to 20 years with an estimated average of about 9 to 12 years [1, 2]. In addition, only around 16% of the drugs that begin preclinical testing are approved for human use [3]. Some of this low success rate can be attributed to the different responses that animals and humans have to the drugs being tested; some drugs have to be withdrawn from market due to toxic effects on human organs such as liver and heart, despite being tested safely on animals. A possible solution to this might be the creation of human pluripotent stem cell (hPSC) -derived micro-tissues which could be used with organ-on-a-chip devices [47]. These micro-tissues are expected to produce the same or similar physiological reaction that the entire organ would but on a much smaller scale. This would result in scalable, faster and potentially more reliable drug testing platform, and hopefully an end to animal testing.

hPSCs are the ideal cells to use for this application due to their ability to self-renew indefinitely, which enables large populations of cells to be created easily in vitro, and their pluripotency which means that they can be differentiated into any required adult cell type [813]. Pluripotent stem cells can be divided into embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). Human ESCs (hESCs) were first isolated from early human blastocysts in 1998 [14]. Any tissue construct created from hESCs for implantation in vivo would require the patient to receive immunosuppressive drugs and ethical issues still restrict some applications due to their source. iPSCs have neither of these drawbacks as they can be created from harvested adult cells from the patient requiring treatment and as such any implanted cells derived from these iPSCs should not be rejected by the patient’s immune system but may require immunosuppressive drugs at a greatly reduced dosage. In 2006 Shinya Yamanaka discovered that iPSCs can be derived from somatic cells by retrovirally transducing them with four transcription factors—Oct3/4, Sox2, Klf4 and C-myc [15, 16]. These cells have the same self-renewal and differentiation capabilities as ESCs but with the added advantage that iPSCs can be used for autologous therapies. These unique characteristics make pluripotent stem cells ideal for use in a number of applications such as clinical tissue engineering, novel drug discovery and testing for the pharmaceutical industry [8,9, 17, 18].

In the field of biofabrication, great advances are being made towards fabricating 3D tissue and organs with very fine spatial control of cell deposition. From the very first paper that was published investigating printing of biological cells (or bioprinting), tissue engineering was identified as a major application for this new technology [19]. If more complex structures such as organs and tissues were to be printed, the bioprinter would need the ability to transfer microscopic patterns of viable cells of multiple cell types into well-defined three-dimensional arrays that closely mimic the tissue structure. There has been much progress in the development and establishment of several different bioprinting techniques for 3D live constructs [2022] including those based on laser pulses, inkjets and other more novel approaches. It is an inescapable fact that cells will be subjected to some level of stress during deposition, regardless of the printing technique being used. For example, cells printed by non-contact methods will be affected when they impact on the substrate at some incident velocity, which would result in extreme deceleration and shear stress [2326]. Shear stress is applied to cells pushed through nozzle orifices and capillary tubes [24, 2742] and the actuation is provided via pressure, heat, or high frequency vibration which can also be damaging to the cells [30, 31, 4346]. If cells are exposed to laser energy the radiation can cause genetic damage [29, 4754] and shear forces are applied during cavitation and jet formation [23, 55]. Ultrasonic actuation for cell transfer would subject the cells to stress in the form of heat and vibration [56, 57]. Therefore, it is important to validate the response of printed cells to any particular bioprinting process in terms of their viability and more importantly their biological functions.

We previously reported the results of the first experiments printing hESCs using a valve-based printing approach including their response to the printing process in the form of post-printed viability and pluripotency validation [37]. However, if hPSCs are to be used for producing human tissues on demand for drug testing, their post-printing differentiation must be reproducibly directed to the required lineages for each tissue. Unfortunately homogenous cellular differentiation of hPSCs into some germ layers has proved difficult [12, 13]. Here, we report the first investigation into the bioprinting of human iPSCs, their response to the valve-based printing process as well as their post-printing differentiation into hepatocyte-like cells (HLCs). HLCs that are in the process of differentiating are bioprinted and examined to further validate the compatibility of the valve-based bioprinting process with fragile cell transfer. Finally, 3D hydrogel structures were designed and printed out with encapsulated hESC-derived HLCs and the viability and hepatic characteristics of the cells were investigated.


A newer version of our previously reported cell printing platform [37] has been developed. Four nanolitre dispensing systems, each comprising a solenoid valve (VHS Nanolitre Dispense Valve, Lee Products Ltd) with 101.6 μm internal diameter nozzles (Minstac Nozzle, Lee Products Ltd), were attached to static pressure reservoirs for the bio-ink solution to be dispensed from via flexible tubing. The nanolitre dispensing system and bio-ink reservoirs were mounted onto the tool head of an enclosed custom built micrometer-resolution 3-axis XY–Z stage (figure 1). This newer cell printing platform improved on the previous version by reducing the overall size and weight of the machine, allowing it to be mounted inside a standard tissue culture hood during experiments requiring a sterile environment. Other enhancements included the two extra nanolitre dispensing systems, taking the total up to four, a more robust electronics and custom firmware was developed which improved the reliability and speed of the machine and two separate pressure channels were included, allowing for differential bio-ink dispensing conditions. Unless otherwise stated standard printing conditions were used: for 2D, printing was carried out using a pulse time of 8 ms at an inlet pressure of 0.6 bar using a nozzle with an internal diameter of 101.6 μm; for 3D, printing was carried out using a pulse time of 400 μs at an inlet pressure of 1.0 bar for sodium alginate solution and a pulse time of 400 μs at an inlet pressure of 0.5 bar for calcium chloride solution both using nozzles with an internal diameter of 101.6 μm.

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Figure 1. (a) Schematic drawing of the cell printer system; (b) detailed schematic of the micro-solenoid valve; (c) schematic of the combinatorial printing process for alginate hydrogel creation; (d) a 3D printed alginate tube structure approximately 13 mm tall printed with 1.5% w/v Sodium Alginate and 600 mM (6%) Calcium Chloride solutions in Millipore water (scale bar 2 mm).



The process of in vivo liver organogenesis occurs in the developing foregut, when newly specified hepatic cells separate from the endodermal sheet and form a dense 3D structure known as a hepatoblast (liver bud) [74, 75]. It is hypothesized that arranging the hESC–HLCs in 3D during the differentiation process may yield more mature hepatocytes than conventional 2D differentiation. The hESC differentiation protocols are more efficient and robust than hiPSC protocols therefore only hESC-derived HLCs were printed in 3D.

In order for this technique to be useful for tissue engineering applications, structures need to be tall enough to allow cells to interact in a three-dimensional environment. The concentration of alginate solution was set to 1.5% w/v to improve the mechanical strength of the hydrogel and allow it to support further layers. Circular structures with a large number of layers were designed and printed out in the wells of a multi-well plate to allow the structures to be cultured post-printing. These resulting structures were photographed for analysis and are shown in figure 7below.

These structures were printed out in a matter of minutes and are strong enough to support their own weight and the weight of further layers (as seen in figure 1(d)). The structures spread slightly, but by slightly altering the volume ratio, concentrations and surface properties this spreading can be reduced.

Approximately one hour post-printing one of the HLC-laden alginate ring structures was examined using a confocal microscope; the 3D image is shown in figure 8(a). Cell viability was calculated to be 55.5% using the Imaris confocal microscope software. Cell viability declined over the first 24 h which resulted in low cell numbers for hepatic marker testing following the 3D differentiation process, but the viability remained stable for the remainder of the differentiation process. At day 23 of the differentiation process, the cells in the remaining structures were harvested and stained for the presence of hepatic markers. As shown in figure 8(b), cells are positive for albumin which demonstrates their hepatic lineage. The normal time required for 2D differentiation of hPSC-HLCs is 17–24 d. However, based on the results of albumin secretion in the medium, we observed the 3D printed cells have taken longer to reach the maximum albumin secretion than the 2D control as shown in figure 8(c). Interestingly, when analyzing the difference between 20 and 40 layer printed tube structures, we noticed close-to proportional increase in albumin secretion to the number of layers as shown in figure 8(d). This indicates that the permeability of the alginate hydrogel allows nutrition and differentiation reagents to enter the structure and support 3D differentiation and maturation processes of the cells, regardless of the height of the printed structure.

Research is currently underway including investigations to improve the 3D viability and adjusting the differentiation protocol that may facilitate higher albumin secretion. For example, the optimization of hydrogel formation as well as enhanced cell density may improve the differentiation process for hPSCs in 3D [21, 76, 77].

4. Conclusions

To the best of our knowledge, this study is the first to demonstrate that hiPS cells can be bioprinted without adversely affecting their biological functions including viability and pluripotency. Importantly, we verified that our valve-based printing process is gentle enough to not affect the pluripotency of both hESCs and hiPSCs. A number of different hPSC lines were directed to differentiate into HLCs. Cells were printed during the differentiation process and showed no differences in hepatocyte marker expression and similar morphology when compared to a non-printed control. We previously reported the results of an investigation into the response of hESCs to the valve-based printing process. Here we build on that study, performing a deeper investigation to compare the response of hiPSCs and hESCs to the printing process using flow cytometry. The effect of nozzle geometry was investigated and the effects of nozzle length on the post-printing viability of cells were recorded; longer nozzles lower the post-printing viability of the cells. We printed hESC-derived HLCs in a 3D alginate matrix and tested for viability and hepatic markers during the remaining differentiation and they were found to be hepatic in nature. The ability to bioprint hPSCs while either maintaining their pluripotency or directing their differentiation into specific cell types will pave the way for producing organs or tissues on demand from patient specific cells which could be used for animal-free drug development and personalized medicine.



Large scale industrialized cell expansion: producing the critical raw material for biofabrication processes

Arun Kumar1 and Binil Starly1,2


Cellular biomanufacturing technologies are a critical link to the successful application of cell and scaffold based regenerative therapies, organs-on-chip devices, disease models and any products with living cells contained in them. How do we achieve production level quantities of the key ingredient—’the living cells‘ for all biofabrication processes, including bioprinting and biopatterning? We review key cell expansion based bioreactor operating principles and how 3D culture will play an important role in achieving production quantities of billions to even trillions of anchorage dependent cells. Furthermore, we highlight some of the challenges in the field of cellular biomanufacturing that must be addressed to achieve desired cellular yields while adhering to the key pillars of good manufacturing practices—safety, purity, stability, potency and identity. Biofabrication technologies are uniquely positioned to provide improved 3D culture surfaces for the industrialized production of living cells.

Biofabrication of tissue constructs by 3D bioprinting of cell-laden microcarriers

Riccardo Levato1,2, Jetze Visser3, Josep A Planell1, Elisabeth Engel1,2,4, Jos Malda3,5 andMiguel A Mateos-Timoneda2,1


Bioprinting allows the fabrication of living constructs with custom-made architectures by spatially controlled deposition of multiple bioinks. This is important for the generation of tissue, such as osteochondral tissue, which displays a zonal composition in the cartilage domain supported by the underlying subchondral bone. Challenges in fabricating functional grafts of clinically relevant size include the incorporation of cues to guide specific cell differentiation and the generation of sufficient cells, which is hard to obtain with conventional cell culture techniques. A novel strategy to address these demands is to combine bioprinting with microcarrier technology. This technology allows for the extensive expansion of cells, while they form multi-cellular aggregates, and their phenotype can be controlled. In this work, living constructs were fabricated via bioprinting of cell-laden microcarriers. Mesenchymal stromal cell (MSC)-laden polylactic acid microcarriers, obtained via static culture or spinner flask expansion, were encapsulated in gelatin methacrylamide-gellan gum bioinks, and the printability of the composite material was studied. This bioprinting approach allowed for the fabrication of constructs with high cell concentration and viability. Microcarrier encapsulation improved the compressive modulus of the hydrogel constructs, facilitated cell adhesion, and supported osteogenic differentiation and bone matrix deposition by MSCs. Bilayered osteochondral models were fabricated using microcarrier-laden bioink for the bone compartment. These findings underscore the potential of this new microcarrier-based biofabrication approach for bone and osteochondral constructs.

Microstereolithography and characterization of poly(propylene fumarate)-based drug-loaded microneedle arrays

Yanfeng Lu1, Satya Nymisha Mantha1, Douglas C Crowder2, Sofia Chinchilla2, Kush N Shah2,3,4,Yang H Yun2, Ryan B Wicker5 and Jae-Won Choi1


Drug-loaded microneedle arrays for transdermal delivery of a chemotherapeutic drug were fabricated using multi-material microstereolithography (μSL). These arrays consisted of twenty-five poly(propylene fumarate) (PPF) microneedles, which were precisely orientated on the same polymeric substrate. To control the viscosity and improve the mechanical properties of the PPF, diethyl fumarate (DEF) was mixed with the polymer. Dacarbazine, which is widely used for skin cancer, was uniformly blended into the PPF/DEF solution prior to crosslinking. Each microneedle has a cylindrical base with a height of 700 μm and a conical tip with a height of 300μm. Compression test results and characterization of the elastic moduli of the PPF/DEF (50:50) and PPF/drug mixtures indicated that the failure force was much larger than the theoretical skin insertion force. The release kinetics showed that dacarbazine can be released at a controlled rate for five weeks. The results demonstrated that the PPF-based drug-loaded microneedles are a potential method to treat skin carcinomas. In addition, μSL is an attractive manufacturing technique for biomedical applications, especially for micron-scale manufacturing.

Controlling shape and position of vascular formation in engineered tissues by arbitrary assembly of endothelial cells

Hiroaki Takehara1,4, Katsuhisa Sakaguchi2, Masatoshi Kuroda3, Megumi Muraoka3, Kazuyoshi Itoga1,Teruo Okano1 and Tatsuya Shimizu1


Cellular self-assembly based on cell-to-cell communication is a well-known tissue organizing process in living bodies. Hence, integrating cellular self-assembly processes into tissue engineering is a promising approach to fabricate well-organized functional tissues. In this research, we investigated the capability of endothelial cells (ECs) to control shape and position of vascular formation using arbitral-assembling techniques in three-dimensional engineered tissues. To quantify the degree of migration of ECs in endothelial network formation, image correlation analysis was conducted. Positive correlation between the original positions of arbitrarily assembled ECs and the positions of formed endothelial networks indicated the potential for controlling shape and position of vascular formations in engineered tissues. To demonstrate the feasibility of controlling vascular formations, engineered tissues with vascular networks in triangle and circle patterns were made. The technique reported here employs cellular self-assembly for tissue engineering and is expected to provide fundamental beneficial methods to supply various functional tissues for drug screening and regenerative medicine.

The influence of printing parameters on cell survival rate and printability in microextrusion-based 3D cell printing technology

Yu Zhao1,2, Yang Li1,2, Shuangshuang Mao1,2, Wei Sun1,2,3,4 and Rui Yao1,2

Three-dimensional (3D) cell printing technology has provided a versatile methodology to fabricate cell-laden tissue-like constructs and in vitro tissue/pathological models for tissue engineering, drug testing and screening applications. However, it still remains a challenge to print bioinks with high viscoelasticity to achieve long-term stable structure and maintain high cell survival rate after printing at the same time. In this study, we systematically investigated the influence of 3D cell printing parameters, i.e. composition and concentration of bioink, holding temperature and holding time, on the printability and cell survival rate in microextrusion-based 3D cell printing technology. Rheological measurements were utilized to characterize the viscoelasticity of gelatin-based bioinks. Results demonstrated that the bioink viscoelasticity was increased when increasing the bioink concentration, increasing holding time and decreasing holding temperature below gelation temperature. The decline of cell survival rate after 3D cell printing process was observed when increasing the viscoelasticity of the gelatin-based bioinks. However, different process parameter combinations would result in the similar rheological characteristics and thus showed similar cell survival rate after 3D bioprinting process. On the other hand, bioink viscoelasticity should also reach a certain point to ensure good printability and shape fidelity. At last, we proposed a protocol for 3D bioprinting of temperature-sensitive gelatin-based hydrogel bioinks with both high cell survival rate and good printability. This research would be useful for biofabrication researchers to adjust the 3D bioprinting process parameters quickly and as a referable template for designing new bioinks.

A new method of fabricating a blend scaffold using an indirect three-dimensional printing technique

Jin Woo Jung1,3, Hyungseok Lee1,3, Jung Min Hong1, Jeong Hun Park1, Jung Hee Shim2, Tae Hyun Choi2and Dong-Woo Cho1

Due to its simplicity and effectiveness, the physical blending of polymers is considered to be a practical strategy for developing a versatile scaffold having desirable mechanical and biochemical properties. In the present work, an indirect three-dimensional (i3D) printing technique was proposed to fabricate a 3D free-form scaffold using a blend of immiscible materials, such as polycaprolactone (PCL) and gelatin. The i3D printing technique includes 3D printing of a mold and a sacrificial molding process. PCL/chloroform and gelatin/water were physically mixed to prepare the blend solution, which was subsequently injected into the cavity of a 3D printed mold. After solvent removal and gelatin cross-linking, the mold was dissolved to obtain a PCL–gelatin (PG) scaffold, with a specific 3D structure. Scanning electron microscopy and Fourier transform infrared spectroscopy analysis indicated that PCL masses and gelatin fibers in the PG scaffold homogenously coexisted without chemical bonding. Compression tests confirmed that gelatin incorporation into the PCL enhanced its mechanical flexibility and softness, to the point of being suitable for soft-tissue engineering, as opposed to pure PCL. Human adipose-derived stem cells, cultured on a PG scaffold, exhibited enhanced in vitro chondrogenic differentiation and tissue formation, compared with those on a PCL scaffold. The i3D printing technique can be used to blend a variety of materials, facilitating 3D scaffold fabrication for specific tissue regeneration. Furthermore, this convenient and versatile technique may lead to wider application of 3D printing in tissue engineering.


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