**4. Conclusions**

In the last two decades, a lot of attention has been devoted to synthesis and characterization of functionalized iron or other transition metal oxide based MNPs, which have potential use in diagnosis and/or therapy in cancer treatment. These MNPs can act as contrast enhancement agents in diagnostic applications such as MRI and/or they can be used as carriers or localy heat releasers in therapeutic applications such as targeted drug delivery and magnetic hyperther‐ mia, respectively. In the design of MNPs, the selection of the magnetic core and its surface modification with several organic/inorganic materials and polymers plays the major role effecting the performance of MNPs in these biomedical applications. Among different available magnetic ions, the correct selection of the magnetic core for MNPs requires careful and balanced consideration on material's properties such as chemical stability, toxicity and magnetization. The magnetic core further should be crystalline, small than a critical size and have a narrow size distribution where all these requirements together with proper in-situ or post synthetic surface coatings are satisfied by chemical methods like co-precipitation and thermal decomposition method. The surface coating is important for ensuring the biocompat‐ ibility, colloidal stability and functionalization of MNPs, where a wide variety of coating materials are available like organic molecules/ polymers such as chitosan, dextran, Polyethy‐ leneglycol (PEG), Polyethyleneimine (PEI), Polyvinylalcohol (PVA) or inorganic materials like silica and gold. Although much progress has been made on the fabrication of MNPs with delicate structure and enhanced surface properties, in using these MNPs for in vivo applica‐ tions, major challenges still present like degredation, clearence of MNPs in the body, particlecell interactions and changing physiological conditions like pH, temperature, blood pressure etc. which makes difficult to predict the behaivour of MNPs in biological medium.

[8] Varadan, V. K., Chen, L. and Xie, J., Nanomedicine: Design and Applications of Mag‐ netic Nanomaterials, Nanosensors and Nanosystems, John Wiley and Sons Pub.,

Surface Modification of Nanoparticles Used in Biomedical Applications

http://dx.doi.org/10.5772/55746

201

[9] Lascialfari, A. and Sangregorio, C., Magnetic Nanoparticles in Biomedicine: Recent

[10] Casula, M. F., Floris, P., Innocenti, C., Lascialfari, A., Marinone, M., Corti, M., Sperl‐ ing, R. A., Parak, W. J., Sangregorio, C., Magnetic Resonance Contrast Agents Based on Iron Oxide Superparamagnetic Ferrofluids; Chemistry of Materials, 2010, 22 (5),

[11] Masotti, A., Pitta, A., Ortaggi, G., Corti, M., Innocenti, C., Lascialfari, A., Marinone, M., Marzola, A., Daducci, A., Sbarbati, A., Micotti, E., Orsini, F., Poletti, G., Sangre‐ gorio, C., Synthesis and Characterization of Polyethylenimine-based Iron Oxide Composites as Novel Contrast Agents for MRI; Magnetic Resonance Materials in

[12] Umut, E., Pineider, F., Arosio, P., Sangregorio, C., Corti, M., Tabak, F., Lascialfari, A., Ghigna, P., Magnetic, Optical and Relaxometric Properties of Organically Coated Gold-magnetite (Au-Fe3O4) Hybrid Nanoparticles for Potential use in Biomedical Ap‐ plications, Journal of Magnetism and Magnetic Materials, 2012, 324, pp. 2373-2379

[13] Gossuin, Y., Gillis, P., Hocq, A., Vuong, Q. L. and Roch, A., Magnetic Resonance Re‐ laxation Properties of Superparamagnetic Particles, WIREs Nanomedicine and Nano‐

[14] Bridot, J. L., Faure, A. C., Laurent, S., Riviere, C., Billotey, C., Hiba, B., Janier, M., Jos‐ serand, V., Coll, J. L., Vander Elst, L., Muller, R., Roux, S., Perriat, P., Tillement, O., Hybrid Gadolinium Oxide Nanoparticles: Multimodal Contrast Agents for in Vivo

Imaging, Journal of American Chemical Society, 2007, 129 (16), pp. 5076-5084

[15] Kim, D. H., Nikles, D. E., Johnson, D. T., Brazel, C. S., Heat Generation of Aqueously Dispersed CoFe2O4 Nanoparticles as Heating Agents for Magnetically Activated Drug Delivery and Hyperthermia, Journal of Magnetism and Magnetic Materials,

[16] Gonzales, M., and Krishnan, K. M., Synthesis of Magnetoliposomes with Monodis‐ perse Iron oxide Nanocrystal Cores for Hyperthermia, Journal of Magnetism and

[17] Hergt, R. And Dutz, S., Magnetic Particle Hyperthermia-Biophysical Limitations of a Visionary Tumor Therapy, Journal of Magnetism and Magnetic Materials, 2007, 311

[18] Gonzales, M., Zeisberger, M. and Krishnan, K. M., Size-dependent Heating Rates of Iron Oxide Nanoparticles for Magnetic Fluid Hyperthermia, Journal of Magnetism

Advances Chemistry Today, 2011, 29 (2), pp.20-23

2008

pp.1739–1748

Physics, 2009, 22 (2), pp.77–87

biotechnology, 2009, 1, pp. 299-310

2008, 320 (19), pp.2390–2396

(1), pp.187-192

Magnetic Materials, 2005, 293 (1), pp.265–270

and Magnetic Materials, 2009, 321 (13), pp.1947-1950
