Upconversion Nanoparticle-Based Organosilica-Micellar Hybrid Nanoplatforms for Redox-Responsive Chemotherapy and NIR-Mediated Photodynamic Therapy.

Upconversion nanoparticles (UCNPs) can convert near-infrared light (NIR, 980 or 808 nm) to ultraviolet (UV) or visible light, which can be widely used to improve tissue penetration depth in photodynamic therapy (PDT). Herein, we develop a kind of UCNP-based organosilica-micellar hybrid nanoplatform for redox-responsive chemotherapy and NIR-mediated PDT. The nanoplatform was constructed by the self-assembly of block copolymers polystyrene- b -poly (acrylic acid) and oil-soluble UCNPs in the oil/water system and the subsequent organosilica coating with 3-mercaptopropyltrimethoxysilane molecules. To endow the nanosystem with more stability in biological media, polyethylene glycol molecules were further modified via the Michael addition reaction. As a promising nanocarrier, chlorin e6 (Ce6) and doxorubicin (DOX) molecules were loaded into the hydrophobic core and the disulfide-doped organosilica shell, respectively. With endocytosis by SMMC-7721 tumor cells, the Ce6 and DOX coloaded nanosystem was activated by UCNPs through luminescence resonance energy transfer under the irradiation of 808 nm laser, thus generating cytotoxic 1 O 2 for NIR-mediated PDT. Meanwhile, DOX was selectively released because of the redox-responsive biodegradation of the disulfide-doped organosilica shell in the glutathione over-expressed SMMC-7721 tumor cells. Based on these, the chemotherapy/PDT combination toxic feature of the multifunctional nanosystem was further demonstrated in the DOX-resistant MCF-7 tumor cells. On the other hand, the Ce6 and DOX coloaded nanosystem exhibited negligible toxicity to the normal 3T3 cell because of the protective effects of organosilica coating. We envision that the resultant hybrid nanoplatform provides us a promising nanocarrier for the combination therapy of redox-responsive safe chemotherapy and efficient NIR-mediated PDT.