Synthesis and in vitro testing of thermoresponsive polymer-grafted core-shell magnetic mesoporous silica nanoparticles for efficient controlled and targeted drug delivery.

In this work, thermoresponsive polymer grafted magnetic mesoporous silica nanoparticles were prepared, fully characterized and tested as controlled drug delivery systems. For this purpose, iron oxide nanoparticles coated with mesoporous silica shell were grafted with poly(N-isopropylacrylamide-co-3-(methacryloxypropyl)trimethoxysilane) (PNIPAM-co-MPS). The grafting and polymerization on the as-prepared nanoparticles were performed in one-step procedure. Using this methodology, the polymer was successfully grafted mainly onto the silica surface, leaving the mesopores empty for the drug loading. The prepared hybrid nanoparticles (MMSNP-PNIPAM-co-MPS) showed high magnetization saturation (19.5 emu g-1) and high specific surface area (505 m2 g-1) and pore volume (0.29 cm3 g-1). Ibuprofen was used as a model drug to test the performance of the hybrid particles as thermosensitive drug delivery systems. For this, in vitro drug delivery tests were conducted below (25 °C) and above (40 °C) the lower critical solution temperature (LCST) of the polymer (PNIPAM-co-MPS). Considerable difference (80%) in the ibuprofen release at these two temperatures and a fast and complete release of the drug at 40 °C was observed. These results suggest that the thermoresponsive copolymer acts as a gatekeeper for the temperature-controlled release of the drug loaded inside the mesopores. Therefore, MMSNP-PNIPAM-co-MPS are promising magnetic and thermoresponsive nanocarriers for targeted delivery of therapeutic substances.