Leaders in Pharmaceutical Business Intelligence (LPBI) Group

Medical Applications of Nano Magnetite

Author: Danut Dragoi, PhD

Nano magnetite refers to small crystals of Fe3O4 in nano-metric range that preserves some specific magnetic properties of the magnetite bulk crystal such as the magnetism at saturation, Curie temperature, coercive magnetic force, hysteresis loop, etc. A discussion of medical applications of nano-magnetic particles is shown in here.

Opportunities for magnetite nanoparticles to be effectively incorporated into environmental contaminant removal and cell separation ([1] Honda et al., 1998;[2] Ebner et al.,1999; [3] Rikers et al., 1998; [4] Navratil, 2003), magnetically guided-drug delivery (Roger et al., 1999), magnetocytolysis ([5] Roger et al., 1999), sealing agents (liquid O-rings) ([6] Enzel et al., 1999), dampening and cooling mechanisms in loudspeakers ([6] Enzel et al., 1999), and contrasting agents for magnetic resonance imaging (MRI) ([7] Schütt, 2004). Advancement of synthesis and stabilization procedures towards production of uniformly sized, dispersed (potentially embedded) magnetite nanoparticles has clearly inspired creative imagination and application in various fields. The following subsections address two topics, magnetic guided drug delivery and magnetic resonance tomography which  helps us  better understanding the capabilities offered by magnetite nanoparticles.

Magnetically Guided Drug Delivery

Ferrofluids containing encapsulated (with biologically compatible surface chemistries) magnetite nanoparticles, as described above, can be employed for drug delivery to specific locations. Exploitation of superparamagnetic magnetization of magnetite nanoparticles allows for “magnetic dragging” of internal (present in bloodstream or elsewhere) magnetite nanoparticles carrying DNA, enzymes, drugs to target-areas. Similarly, biological effectors, which are proteins (containing DNA specific to target cells) incorporated into encapsulated nanoparticle surface functionality, allow for target cell specificity. Once biological effector carrying magnetic nanoparticles bind to target-cells, the applied magnetic field is fluctuated (approximately 1 MHz) causing magnetocytolysis, or cell destruction, which eliminates target-cells. Similarly, after being dragged to target areas, magnetocytolysis of encapsulated nanoparticles can release drugs. Research towards these ends is currently being heavily investigated as potential for novel drug/cancer treatment abounds. ([5] Roger et al., 1999). Picture below shows schematically drug-loaded magnetic nanoparticles targeting for tumor therapy in which the magnetic nanoparticles are noninvasively moved toward the target.

Image SOURCE:https://books.google.com/books?hl=en&lr=&id=oX32CwAAQBAJ&oi=fnd&pg=PA425&ots=1EDRtu7mDx&sig=fYjckTZEyXCkOBb4sjRAuWSR_U4#v=onepage&q&f=false

Magnetic Resonance Tomography

Magnetic Resonance Tomography (MRT) permits noninvasive visualization of cross-sectional images of the human body, tissues, and organs ([7] Schütt, 2004). The MRT technique provides better tissue resolution than traditional radiation based technologies; with addition of contrasting agents, this resolution can be further enhanced ([8] Shao et al., 2005). Magnetite nanoparticles (in ferrofluid form) are powerful contrasting agents due to their paramagnetic magnetization. Ferrofluid physico-morphosis under magnetic field Blaney 65 Human bloodstreams readily reject the nanoparticle colloidal solution, which quickly passes into the liver ([8] Shao et al., 2005). Consequently, ferrofluids have thus far only been useful in distinguishing between healthy and malignant liver cells. This limitation can be overcome through functionalization of magnetite nanoparticles with various ligands that allows for organ-specific transport; therefore, MRT imaging of various bodily organs can be possible. Furthermore, polymeric (i.e., polyethylene oxide – PEO) coating of functionalized magnetite particles permits ferrofluids longer bloodstream retention. ([7] Schütt, 2004) PEO coatings are applied through magnetite interaction with copolymer PEO-polypeptide; polypeptides interact with the positively charged magnetite surface and provide nanoparticle masking to allow longer bloodstream residence. These coated magnetite nanoparticles could also be employed as extremely efficient capsules for drug delivery systems, which are discussed by ([7] Schütt, 2004).

References

[1] Honda H, Kawabe A, Shinkai M, and Kobayashi T (1998). Development of chitosan-conjugated magnetite for magnetic cell separation. Journal of Fermentation and Bioengineering 86, 191-196

[2] Ebner AD, Ritter JA, Ploehn HJ, Kochen RL, and Navratil JD (1999). New magnetic field-enhanced process for the treatment of aqueous wastes. Separation Science and Technology 34, 1277-1300

[3] Rikers RA, Voncken JHL, and Dalmijn WL (1998). Cr-polluted soil studied by high gradient magnetic separation and electron probe. Journal of Environmental Engineering 124, 1159-1164

[4] Navratil JD (2003). Adsorption and nanoscale magnetic separation of heavy metals from water. U.S. EPA workshop on managing arsenic risks to the environment: characterization of waste, chemistry, and treatment and disposal. Denver, CO

[5] Roger J, Pons JN, Massart R, Halbreich A, and Bacri JC (1999). Some biomedical applications of ferro fluids. Eur. Phys. J. AP 5, 321-325

[6] Enzel P, Adelman N, Beckman KJ, Campbell DJ, Ellis AB, Lisensky GC (1999). Preparation of an aqueous-based ferrofluid. J. Chem. Educ. 76, 943-948

[7] Schütt D (2004). Magnetite colloids for drug delivery and magnetic resonance imaging. Institute Angewandte Polymerforschung: thesis Selim MS, Cunningham LP, Srivastava R, Olson JM (1997). Preparation of nano-size magnetic gamma ferric oxide (γ-Fe2O3) and magnetite (Fe3O4) particles for toner and color imaging applications. Recent Progress in Toner Technologies, 108- 111

[8] Shao H, Lee H, Huang Y, Kwak BK, and Kim CO (2005). Synthesis of nano-size magnetite coated with chitosan for MRI contrast agent by sonochemistry. Magnetics Conference, 2005. INTERMAG Asia 2005. Digests of the IEEE International, 461-462

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