A versatile synthetic route towards gelatin-silica hybrids and magnetic composite colloidal nanoparticles

We report a versatile synthetic route for the preparation of nearly monodispersed spherical gelatin-silica hybrid nanoparticles. These hybrids have been synthesized by means of a non-emulsion sol-gel method involving the base-catalyzed hydrolysis and condensation of gelatin modified with different functional coupling agents. The method is effective for preparing hybrids of both gelatin type A and B, and the alkoxysilane coupling agents 3-isocyanatopropyltriethoxysilane (ICPTES) and 3-glycidoxypropyltrimethoxysilane (GPTMS). The ensuing gelatin-silica hybrid nanoparticles are spherical and uniform in morphology, with average sizes between 100 and 120 nm. The ICPTES seems to be more adequate to produce uniform nanospheres with narrow size distribution regardless the type of gelatin, while using GPTMS increases the roughness of the particles' surface. The hybrids are thermo-sensitive in the temperature range 25-70 degrees C, undergoing reversible volume transitions in response to thermal stimuli, which is of great relevance for biomedical applications such as thermally controlled drug-delivery systems. The synthetic approach was successfully employed to coat magnetic iron oxide nanoparticles with thin shells of a few nanometers of hybrid composition to obtain hybrid nanoparticles with magnetic features.