(187b) Nanomagnets and Polymers: Design of Vehicles for Medical Theranostics

The combination of nano-scale magnetic particles with biocompatible polymers affords opportunities for multifunctional devices for theranostics applications. In particular, further combination with targeting ligands allows therapies and medical diagnostics to be conducted on a cellular or sub-cellular level. In the area of diagnostics, magnetic nanoparticles have proven useful as phase contrast agents for MRI, and although most do not provide contrast enhancement as great as gadolinium, iron oxide-based materials offer additional functionality such as localization or magnetic hyperthermia in addition avoiding the toxicological issues observed with gadolinium. The application of static magnetic fields can collect magnetic nanoparticles in simulated blood flow to focus the therapeutic effect in a region of interest. By applying high frequency (kHz-MHz) magnetic fields, iron oxide and other magnetic nanoparticles generate significant heat, which can be harnessed for magnetothermal therapies, which has been used successfully in cancer treatment. Polymer coatings are used to improve biocompatibility and decrease particle aggregation. Surface chemistry plays an important role in determining hydrodynamic sizes and the stability of nanoparticle dispersions. The polymers can also host drugs and deliver them to targeted cells and tissue. Specifically, the combination of magnetic hyperthermia with thermally responsive polymers, such as copolymers of poly(N-isopropyl acrylamide), which display a lower critical solution temperature between 37-45 ^oC, or nanocrystalline polycaprolactone, which melts around 40-45 ^oC, have proven useful for magnetically-activated drug release. Optimization of these systems, including nanoparticle and polymer design, will be discussed.