A Red Light-Triggered Drug Release System Based on One-Photon Upconversion-Like Photolysis.

Photoresponsive drug release systems can enhance drug accumulation at the sites where light is applied. Nowadays, the photocleavable groups used in the systems usually require ultraviolet or blue light irradiation, which limits tissue penetration depth and is harmful to normal cells and living bodies. A one-photon upconversion-like photolysis strategy, which can cleave green light-activatable prodrugs with red light at the presence of a red light-excitable photosensitizer in organic solvents, is developed. However, both the prodrug and photosensitizer are hydrophobic and their energy transfer process is sensitive to oxygen molecules. Here, a simple strategy to address these problems by loading the two components in biocompatible and biodegradable polymeric micelles, is presented. The developed low-irradiance red light-triggered drug release system has a size around 40 nm and exhibits good stability in aqueous solutions. The micellar encapsulation protects the photolysis reaction from oxygen quenching in normoxia aqueous solutions. The therapeutic effect of the system enhanced by the redlight irradiation is demonstrated through in vitro and in vivo studies, indicating promising potential in cancer therapy. The study provides the first example and also an important reference for applying one-photon upconversion-like photolysis in biomedical applications.