Upper critical solution temperature polymer-grafted hollow mesoporous silica nanoparticles for near-infrared-irradiated drug release.

Near-infrared (NIR) irradiation responsive drug delivery systems have many advantages, which have attracted extensive interest from researchers. In this study, a NIR-triggered drug release system was established by grafting upper critical solution temperature (UCST) polymers on the surface of hollow mesoporous silica nanoparticles (HMSNs) followed by treatment with the photothermal conversion agent indocyanine green (ICG). The as-prepared UCST polymers showed the clearing temperature of 45 °C, which were advantageous to serve as gatekeepers in the physiological environment (37 °C). Under NIR irradiation, the temperature of the solution was elevated above the clearing point due to the presence of ICG; consequently, the collapsed UCST polymer chains became more hydrophilic; this resulted in the exposure of the mesoporous channels of the HMSNs and achievement of a burst drug release. Moreover, this NIR-responsive delivery system showed good biocompatibility and high anticancer efficiency towards the MCF-7 cancer cells upon exposure to NIR irradiation. In addition, a synergistic effect of thermal and chemo treatment has been achieved by the application of NIR irradiation since cancer cells are more vulnerable to high temperatures than normal cells.