Organic–Inorganic Magnetic Nanoparticles Based on Magnetite Coated with Molecularly Imprinted Polymers for Drug Delivery Systems

New magnetic organic/inorganic hybrid nanoparticles were prepared by coating the magnetite surface with molecularly imprinted polymers of different monomers (methacrylic acid, itaconic acid, 1-vinylimidazole, 4-vinylpyridine). Magnetite was synthesized by coprecipitation, and polymeric coatings were induced by thermal heating and magnetic hyperthermia. The resultant nanocomposites were tested as Drug Delivery Systems (DDS) of 6-mercaptopurine (6-MP), displaying an interesting behavior depending on (a) the synthesis method used for their preparation and (b) the conditions employed for the release test. DDS based on methacrylic acid displayed the best performance in the release of 6-MP in all cases, but the rationalization of a magnetite MIP (molecularly imprinted polymer) system of this monomer enhanced the release yield by approximately 50% compared with the nonimprinted system (NIP) prepared with the same monomer. New MNP obtained are able to behave as DDS under magnetic hyperthermia with a moderate performance in contrast to the release in the absence of magnetic field.