Induction heating and controlled drug release from thermosensitive magnetic microgels

Poly-N-isopropyl acrylamide (PNIPAM) is a biocompatible thermosensitive polymer that exhibits reversible volume phase transition from a hydrophilic coil to hydrophobic globule at the lower critical solution temperature (LCST) of 32 $^{o}$C. To stimulate conformational change we introduced magnetite nanoparticles (size $\sim $12 nm) in the PNIPAM matrix. The PNIPAM/magnetite nanoparticles composite was then exposed to an alternating magnetic field at a frequency of 380 kHz to induce heating in the nanoparticles by Neel and Brownian relaxations. We report \textit{in vitro} controlled release of anti-cancer drug mitoxantrone which was loaded into PNIPAM/magnetite nanoparticles composite, driven solely by the heating induced by the external magnetic field. We found that the drug released reached 4{\%} in only 4 minutes of heating to 50 $^{o}$C. We also present results on dielectric and magnetic anomalies near the LCST of the PNIPAM-Fe$_{3}$O$_{4}$ composite.