(346a) Surface Initiated Polymerization on Magnetite Nanoparticles with Novel Fluorescent-Thermo Responsive Polymeric Shells for Biomedical Applications

Surface modification of magnetic nanoparticles with stimuli responsive polymers has been studied for some biomedical applications such as drug release, bioadhesion mediators, and micro fluidic devices. These polymers are sensitive to temperature and/or pH changes, which allow modifications in their matrix structure. We have studied surface initiated polymerization on magnetite nanoparticles with acrylamide based thermo responsive polymers such as N-isopropylacrylamide (NIPAM), N-isopropyl-methacrylamide (NIPMAM), and a fluorescent modified acrylamide (FMA) monomer for biomedical applications. The basis of this nano magnetic fluorescent-thermometer is the combination of three properties: the energy dissipation from magnetic nanoparticles upon the application of an oscillating magnetic field, the decrease in the micro-environmental polarities near the main chain of the NIPAM-NIPMAM co-polymer with increasing temperature at specific phase transition point, and the fluorescent properties of the FMA polymers whose intensities increase with decreasing polarity of their microenvironment. X-Ray diffraction was used to characterize the structure of the synthesized nanoparticles, showing a crystalline phase consistent with that of ferrite, and a crystallite size of about 13 nm. FTIR spectroscopy indicated the presence of acrylate groups (C=C) on the nanoparticles surface. Characteristics bands of the acrylamide polymers were also identified by this technique. Fluorescence measurements at temperatures ranging from 25 to 45 °C confirmed the fluorescent-thermo sensitive response of the NIPAM-NIPMAM-FMA co-polymer showing a phase transition point at 38 °C.