Reversible crosslinking terpolymer shell-based mesoporous silica nanoparticles as on-off nanocarriers for pyrene-releasing application

Mesoporous silica nanoparticles (MSNs) were successfully endowed with on-off transport ability and stimuli-responsive property through surface modification. The MSNs with large specific surface areas were synthesized using optimized Stöber method, and then successively modified by amino- and 2-bromoisobutyrate-functionalization. Finally, MSNs grafted with reversible crosslinking terpolymer (MSNs-g-PDMV) were achieved through surface-initiated atom transfer radical polymerization. The resultant MSNs-g-PDMV and their intermediates were confirmed by TEM, SEM, XPS, FTIR, and so on. Pyrene was chosen to evaluate their drug loading and controlled release properties. Owning to crosslinkage and decrosslinkage of coumarin unit in PDMV under different ultraviolet (UV) irradiations, the polymeric chains substantially acted as on-off gate of MSNs to control the transport channel in mesoporous silica shell. The pyrene encapsulation percentage (31.6%) of MSNs-g-PDMV under the irradiation at 365 nm was only half of that under dark condition (60.3%). Cumulative release efficiency under the irradiation at 365 nm was obviously lower than that at 254 nm at the same temperature. In addition, thermal-responsive property of PDMV offered polymeric MSNs temperature sensitivity. Compared with pyrene-releasing experiment at 25 °C, a moderate drop in release efficiency occurred at 45 °C regardless of 254 nm or 365 nm UV irradiation.