A Near-Infrared Photothermal Effect-Responsive Drug Delivery System Based on Indocyanine Green and Doxorubicin-Loaded Polymeric Micelles Mediated by Reversible Diels-Alder Reaction

Near-infrared light (NIR) possesses great advantages for light-responsive controllable drug release, such as deep tissue penetration and low damage to healthy tissues. Herein, a NIR-responsive drug delivery system is developed based on a NIR dye, indocyanine green (ICG), and anticancer drug, doxorubicin (DOX)-loaded thermoresponsive block copolymer micelles, in which the drug release can be controlled via NIR irradiation. First, block copolymers, poly(oligo(ethylene glycol) methacrylate)-block-poly(furfuryl methacrylate) (POEGMA-b-PFMA), are synthesized by sequential reversible addition-fragmentation chain-transfer (RAFT) polymerization, followed by modification with N-octyl maleimide through Diels-Alder (DA) reaction to produce POEGMA-b-POMFMA. The self-assembly of POEGMA-b-POMFMA by nanoprecipitation in aqueous solution affords the polymeric micelles which are used to simultaneously encapsulate ICG and DOX. Upon irradiation by NIR light (805 nm), the loaded DOX is released rapidly from the micelles due to partial retro DA reaction and local temperature increase-induced faster drug diffusion by the photothermal effect. Cytotoxicity evaluation and intracellular distribution observation demonstrate significant synergistic effects of NIR-triggered drug release, photothermal, and chemotherapy toward cancer cells under NIR irradiation.