Fast Biosensors for Pathogens in Food Using Sensitive Micro-Cantilevers Array
Reporter: Danut Dragoi, PhD
The novel biosensor developed by scientists at Rice University in collaboration with colleagues in Thailand and Ireland may make the detection of pathogens much faster and easier for food-manufacturing plants, see link in here .
How is it working?
The picture below taken from, see link here, shows an array of sensitive cantilevers that are functionalized with a specific antibody or peptide that binds to a pathogen that we believe is in the food we like to inspect. A general working principle for cantilevers is shown in here, where a bimorph piezoelectric materials, the sensor, with four electrodes deposited in an asymmetric position on the two parallel sides of a cantilever produce an electric signal once the tip is bended or is under a small weight or force. Other micro-cantilevers use different sensors to maximize the sensitivity. If the pathogen binds specifically to a deposited antibody or peptide on a sensitive cantilever, the free tip of the cantilever will deflect down under the weight of the pathogen. The deflection down of the micro-cantilever can be associated with a reflected laser beam deviation on a position sensitive detector that outputs an electrical signal that can be further processed. In this way, we know what specific pathogen is binding to a known micro-cantilever, so that we can identify the pathogen and from the strength of the signal, the amplitude of the deviation, we may be able to say how much or what concentration of the pathogen is in the food. A laser version of the electronic micro-cantilever exists, see link in here. The picture below shows an array of seven micro-cantilever that binds to seven different pathogens due to the fact that each micro-cantilever has different active antibody or peptide specific to bind on a pathogen.
Image Source: http://bioengineer.org/researchers-develop-fast-biosensor-for-pathogens-in-food/
Figure below shows construction details of one cantilever used by the authors of the paper published, link in here. The yellow color designates the Gold layer deposited on a Si substrate. This Au/Si micro-cantilever shown do not use a sensor attached to it because it may cause a poor sensitivity to small amounts of pathogens detected.
Image Source: http://pubs.acs.org/doi/abs/10.1021/ac403437x
A study on this research appears online this month in the American Chemical Society journal Analytical Chemistry, see link in here.
Advantages of the technique
The process appears to easily outperform tests that are now standard in the food industry. The standard tests are slow because it can take days to culture colonies of salmonella bacteria as proof, or laborious because of the need to prepare samples for DNA-based testing.
The Rice process delivers results within minutes from a platform that can be cleaned and reused. The technology can be easily customized to detect any type of bacteria and to detect different strains of the same bacterium.
The “diving boards” are a set of microcantilevers, each of which can be decorated with different peptides that have unique binding affinities to strains of the salmonella bacteria. When a peptide catches a bacterium, the cantilever bends over so slightly, due to a mismatch in surface stress on the top and bottom. A fine laser trained on the mechanism catches that motion and triggers the alarm.
The system is sensitive enough to warn of the presence of a single pathogen, according to the researchers, who wrote that very low pathogen concentrations cause foodborne disease.
The authors
From the article published on line, see link in here, we can envision the direction and the applications of the research in the future.
The idea springs from research into the use of microcantilevers by Rice biomolecular engineer Sibani Lisa Biswal and lead author Jinghui Wang, a graduate student in her lab. Biswal was prompted to have a look at novel peptides by her graduate school friend, Nitsara Karoonuthaisiri, head of the microarray laboratory at the National Center for Genetic Engineering and Biotechnology in Thailand. Karoonuthaisiri is also a visiting scientist at the Institute for Global Food Security at the Queen’s University, Belfast.
“She’s been working in this area of pathogenic bacteria and asked if we have thought about trying to use our microcantilevers for detection,” Biswal said. “Specifically, she wanted to know if we could try these novel peptides.”
Karoonuthaisiri and her team had isolated bacteriophage viruses associated with salmonella through biopanning and phage display, a technique to study interactions among proteins, peptides and pathogens. She then derived peptides from the phages that would serve as targets for specific bacteria.
“She said, ‘We spend a lot of time trying to characterize which of these peptides work the best. It looks like you have a platform that can do and quantitate that.’ So that’s where we came in,” Biswal said.
The Rice lab compared the peptides’ performance with commercial antibodies now used for salmonella detection and found the peptides were not only more sensitive but could be used in a multiplexed cantilever array to detect many different kinds of salmonella at once.
“The peptides are very robust,” Biswal said. “That’s why a lot of people like them over antibodies. The peptides can handle harsher conditions and are much more stable. Antibodies are large proteins and break down more readily.
“We’re very excited to see where this will lead,” she said.
Our comment
If the peptide adherence on the cantilever is strong, as the authors suggest, then different microcantilever made of Quartz can be used, knowing that extremely small amounts of pathogen bonded will change the frequency of the microcantilever.In this case the calibration curve is frequency versus weight.
Source:
http://bioengineer.org/researchers-develop-fast-biosensor-for-pathogens-in-food/
Jinghui Wang†, M. Josephine Morton‡, Christopher T. Elliott‡, Nitsara Karoonuthaisiri‡§, Laura Segatori†, and Sibani Lisa Biswal*†, Rapid Detection of Pathogenic Bacteria and Screening of Phage-Derived Peptides Using Microcantilevers, Anal. Chem., 2014, 86 (3), pp 1671–1678
Publication: Rapid Detection of Pathogenic Bacteria and Screening of Phage-Derived Peptides Using Microcantilevers. Jinghui Wang, M. Josephine Morton, Christopher T. Elliott, Nitsara Karoonuthaisiri, Laura Segatori, and Sibani Lisa Biswal. Analytical Chemistry (Article ASAP): http://pubs.acs.org/doi/abs/10.1021/ac403437x
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