Design of thermoresponsive polymeric gates with opposite controlled release behaviors

Abstract

Stimuli-responsive devices are novel tools widely studied in the nanomedicine research field. In this work, magnetic-responsive mesoporous silica nanoparticles (MMSNs) were coated with an engineered thermoresponsive co-polymer. Magnetic cores are used as heating sources when they are exposed to an alternating magnetic field. The polymer structure suffers a change from hydrophilic to hydrophobic state when the temperature is raised above the lower critical solution temperature (LCST) or volume phase transition temperature (VPTT), acting as a gate-keeper of a model drug trapped inside the silica matrix. Fluorescein departure can be tuned employing two different polymer structures on the silica surface which exhibit the same transition temperature (42 °C) but a different grafting density: one of them being a dense crosslinked polymer network and the other one a hairy linear polymer layer. The release profile reveals to be the opposite between these two different coatings, allowing suitable drug release behavior for different clinical situations.