A facile design of smart silica nanocarriers via surface-initiated RAFT polymerization as a dual-stimuli drug release platform

The rational design of hybrid nanostructures with an active core and a modified shell can promote several biological applications. Herein, a coating platform has been developed to obtain monodispersed core-shell magnetic mesoporous silica nanocarriers. The surface of silica shells has been successfully modified by disulfide bonds and the photoresponsive polymer, poly(2-nitrobenzyl acrylate) (PNBA), via RAFT polymerization using azobisisobutyronitrile (AIBN) as a thermal initiator. The results showed that these nanocarriers have nanospherical morphologies with high porosity, large surface areas, and suitable pore volumes. Furthermore, ibuprofen (IBU) as a model drug has been loaded easily into the polymeric nanocontainers with a high loading content, followed by coating with β-Cyclodextrin (β-CD) as effective gatekeeper molecules. Treating these nanocarriers with ultraviolet light causes the photocleavage of o-nitrobenzyl ester moieties contained in the growing polymer chains. The controlled release of the loaded IBU cargo can be achieved by ultraviolet light, or reduction cleavable of the disulfide bond, or both together. Interestingly, the magnetic core can enhance the release process through magnetic guiding and pushing the nanocarriers to the targeted sites by using an external magnet or a directed magnetic field. The prepared photodegradable polymer nanocarriers can be widely applied in the fields of controlled drug delivery systems (DDS) and pharmacologically active polymers.