Potential of magnetic nanoparticles for targeted drug delivery.

Nanoparticles (NPs) play an important role in the molecular diagnosis, treatment, and monitoring of therapeutic outcomes in various diseases. Their nanoscale size, large surface area, unique capabilities, and negligible side effects make NPs highly effective for biomedical applications such as cancer therapy, thrombolysis, and molecular imaging. In particular, nontoxic superparamagnetic magnetic NPs (MNPs) with functionalized surface coatings can conjugate chemotherapeutic drugs or be used to target ligands/proteins, making them useful for drug delivery, targeted therapy, magnetic resonance imaging, transfection, and cell/protein/DNA separation. To optimize the therapeutic efficacy of MNPs for a specific application, three issues must be addressed. First, the efficacy of magnetic targeting/guidance is dependent on particle magnetization, which can be controlled by adjusting the reaction conditions during synthesis. Second, the tendency of MNPs to aggregate limits their therapeutic use in vivo; surface modifications to produce high positive or negative charges can reduce this tendency. Finally, the surface of MNPs can be coated with drugs which can be rapidly released after injection, resulting in targeting of low doses of the drug. Drugs therefore need to be conjugated to MNPs such that their release is delayed and their thermal stability enhanced. This chapter describes the creation of nanocarriers with a high drug-loading capacity comprised of a high-magnetization MNP core and a shell of aqueous, stable, conducting polyaniline derivatives and their applications in cancer therapy. It further summarizes some newly developed methods to synthesize and modify the surfaces of MNPs and their biomedical applications.