Photodynamic Therapy with Liposomes Encapsulating Photosensitizers with Aggregation-Induced Emission

As a noninvasive treatment, photodynamic therapy (PDT) is a promising strategy against tumors. It is based on photosensitizer (PS)-induced phototoxicity after irradiation. However, most clinically approved PSs will be widely distributed in normal tissues, especially in the skin, where they will induce phototoxicity on exposure to light. Therefore, patients must remain in a dark room for up to several weeks during or after a PDT. Herein, we proposed a strategy of aggregation-induced emission PSs (AIE-PSs) entrapped in liposomes with controlled photosensitization. The AIE-PSs begin to lose their photosensitivity when entrapped in liposomes. After liposomes have carried AIE-PSs into tumor tissues, the AIE-PSs will be released and immediately reaggregate in a targeted area as the liposomes are decomposed. Their photosensitivity can be triggered at turn-on state and induce cytotoxicity. Two different types of AIE molecules were synthesized and entrapped by liposomes, respectively, to verify the PDT features against tumors in vitro and in vivo. The results indicate that, using this strategy, the photosensitivity of AIE-PS can be controlled and PDT can be treated under normal working conditions, not necessarily in a dark room.