Bio-Medical Application Note

Using the Magnetic Nano Particles Developer Kit in Biomedical Applications

Dry surfactant coated particles when dissolved in an appropriate solvent form a stable colloid. These and other products in the kit (except for EMG1111) are referred to as ferrofluids.

When a magnetic field is applied, a ferrofluid acquires a net magnetic moment due to the orientation of particles in the field direction. These fluids exhibit no remanence or hysteresis. The maximum obtainable moment per unit volume is proportional to the loading density of the magnetic material and is characterized in ferrofluid products as the saturation magnetization value. At saturation, all the particles have their magnetic moments aligned with the external field. Above saturation, the magnetization of fluid is independent of the applied field.

The magnetic particles contained in ferrofluids have a nominal diameter of 10 nm (0.01 microns) and are single domain. Some distribution of particles may, however, be noted in TEM measurements. Stable colloidal suspensions in water are available from 1.7 volume percent to 5.0 volume percent of magnetic particles. The cores of these particles are made of iron oxides which are known to be compatible with living tissues. From the X-ray measurements, the iron oxides are identified to be a mixture of Fe₃O₄ and gamma-Fe₂O₃.

In biomedical applications, the magnetic particles in ferrofluids are used either directly or as a component of polymeric supports for biologically active species. The magnetic properties of these supports allow them to be rapidly separated from complex liquid mixtures even by relatively weak magnetic fields. Depending on the nature of the biologically active species absorbed on the surface of the support; viruses, bacteria, and various cells may be selectively separated.Therapeutic agents have been incorporated into or onto the magnetically active polymer particles. The particles are concentrated by magnetic fields at specific body sites where they deliver high local concentration of drug. Ferrofluids have also been used to incorporate magnetic particles into preformed, biologically active polymer gels which are then used as supports for affinity chromatography. The simplified separation is made possible due to the magnetic properties of the gels and eliminates the usual centrifugation and column chromatography steps.

The advantage of using magnetic polymers in affinity chromatography lies in that they allow a rapid absorption of molecules from colloidal solutions or those containing cell debris. Conventional purification methods do not allow for such a quick retrieval. This method is particularly valuable if the requirement is to rapidly isolate labile enzymes or enzyme complexes after their liberation from the cell. It is likely that once the enzyme is affinity-absorbed within the pores of a gel, it is more protected, for example, against proteolysis enzymes.

Ferrotec Corporation offers a starter “Magnetic Nano Particles Developer Kit” consisting of:

1. A selection of dry particles with different types of surface modifications
2. Water-base ferrofluids stabilized with anionic or cationic surface active agents
3. A slurry of magnetic particles. The slurry serves two main purposes: first, it allows the researcher to coat the particles with his/her own surfactant and second, some researchers require uncoated particles as reference sample.

Bibliography

1. Anderson, L. and Mosbach, K.: Magnetic Ferrofluids for Preparation of Magnetic Polymers and their Application in Affinity Chromatography, Nature, 270, 259 (1977).
2. Czerlinski, G. Senyei, A., and Widder, K.; Magnetic Guidance of Drug CarryingMicrospheres, Journal of Applied Physics, 49, (6), 3578, (1978).
3. Giaever, I.; Magnetic Separation of Biological Particles, U.S. Patent Number 3,970,518, July 20, 1976.
4. Hunter, JA.; Ferrography-A New Method for Isolation of Partic1es from Biological Fluids, Journal of Clinical Pathology, 35,689 (1982).
5. Margel, S., Rembaum, A., and Zisblatt, S.;Polyglutaraldehyde; A New Reagent For Coupling Proteins to Microspheres and For Labeling Cell Surface Receptors. II. Simplified Labeling Method By Means of Nonmagnetic and Magnetic Polyglutaraldehyde Microspheres, Journal of Immunological Methods, 28, 341 (1979).
6. Molday, R.S., Rembaum, A., and Yen, S.P.S.; Application of Magnetic Microspheres in Labeling and Separation of Cells, Nature, 268, 437 (1977).
7. Morimoto, Y.; Magnetic Guidance of Ferro-colloid Entrapped Emulsion for Site Specific Drug Delivery. The Chemical and Pharmaceutical Bulletin, (Tokyo) 1,279 (1983).
8. Morimoto,Y.; Biomedical Applications of Magnetic Fluids II., Journal of Phannacobiodynamics,4 (8), 624 (1981).
9. Mosbach, K., and Schroder, U.; Preparation and Application of Magnetic Polymers for Targeting of Drugs, FEBS Letters, 112, (1979).
10. Newbower, R.; Magnetic Fluids in the Blood, IEEE Transactions on Magnetics, MAG.-9, 447, (1973).
11. Ranney, D.F., Senyei, A.E. and Widder, K; Magnetically Responsive Microspheres and Other Carriers for the Biophysical Targeting of Antitumour Agents, Advances in Pharmacological Chemotherapy, 16; 213 (1979) (190 REF.).
12. Rembaum, A., and Dreyer, W.J.; Immunomicrospheres; Reagents for Cell Labeling and Separation, Science, 208, 364 (1980).
13. Scarpelli, D., Senyei, A, and Widder, K.; Magnetic Microspheres: A Model System for Site Specific Drug Delivery in Vivo, Proceedings of the Society for Experimental Biology and Medicine, 58,141 (1978).
14. Senyei, A.E. and Widder, K.; Drug Targeting: Magnetically Responsive Albumin Microspheres-A Review of the System to Date; Gynecology and Oncology, 12 (1): (1981).
15. Senyei, AE., and Widder, K.; Magnetic Microspheres, 1. of Histochemical Cytochemistry, (1981).
16. Sugibayashi, K.; Biomedical Applications of Magnetic Fluids, Biomaterials, (1982).
17. Margel, S., Beitler, U., and Ofarim, M.; Polyacrolein Microspheres As A New Tool In Cell Biology, J. Cell Sci. 56, 157 (1982).

 

A ferrofluid is a stable suspension of submicron size magnetic particles in various carrier liquids. These particles are coated with stabilizers to prevent agglomeration. The physical properties of ferrofluids, such as volatility, environmental capability and viscosity, etc., are mostly determined by the choice of the carrier.