(95s) Magnetothermal Matrices for Controlled Drug Release

Experiments were conducted to study magnetothermally controlled drug release using magnetic nanoparticles imbedded in polymeric matrices. Once a magnetic field is applied, these magnetic nanoparticles in the polymeric matrix will heat up and release small amounts of drugs in a controlled and effective manner in the body. This release capability may one day be used with targeting vectors to noninvasively trigger the release of agents to kill cancer cells. To achieve our goal, we created hydrogels based on poly(N-isopropylacrylamide) or PNIPAAm, a thermally sensitive polymer, and poly(2-Hydroxyethyl methacrylate) or PHEMA, a nonthermally sensitive polymer, that contained magnetic nanoparticles and drugs. At lower temperatures the mesh size of the PNIPAAm matrix swells, releasing the drug and holding the magnetic particles in the polymer. It was proven that the magnetic particles stayed in place in the polymers studies. We looked at the swelling ratios of the hydrogels by themselves, hydrogels loaded with drugs only, hydrogels loaded with magnetic nanoparticles only, and hydrogels loaded with drugs and magnetic nanoparticles to analyze the thermal responsiveness and diffusion characteristics of the hydrogels with each alteration. Drug release experiments using theophylline as a model drug showed that the drugs were released faster at lower temperatures than higher temperatures for the PNIPAAm hydrogels, but were released at approximately the same rate for the PHEMA hydrogels. Another important part of this research was to look at the polymerization of PNIPAAm with hydrophilic comonomers such as methyacrylic acid, acrylic acid, N-vinyl pyrrolidinone and acrylamide. By making these copolymers, the lower critical solution temperature can be increased to create a system that can be activated by temperatures somewhat higher than body temperature (e.g., 43°C). This temperature can be achieved using magnetic nanoparticles with tailored compositions to achieve low Curie temperatures.