Metal-Organic Framework as a Simple and General Inert Nanocarrier for Photosensitizers to Implement Activatable Photodynamic Therapy

There has been a surging interest in the synthesis of activatable photosensitizers (PSs) as they can be selectively activated with minimum nonspecific phototoxic damages for photodynamic therapy (PDT). Conventional strategies to realize activatable PSs are only applicable to a limited number of molecules. Herein, a simple and general strategy to yield activatable PSs by coupling MIL-100 (Fe) (MIL: Materials Institute Lavoisier) with different kinds of PSs is presented. Specifically, when PSs are encapsulated into MIL-100 (Fe), the photosensitization capability is suppressed due to their isolation from O-2. After the reaction between iron(III) in MIL-100 (Fe) and H2O2 occurs, the framework of MIL-100 (Fe) collapses and the encapsulated PSs regain contact with O-2, leading to activation of photosensitization. In addition, the decomposition of H2O2 can generate O-2 to relieve tumor hypoxia and enhance PDT effect. As O-2 is an indispensable factor for PDT, the activation strategy should be generally applicable to different PSs for activatable PDT.