Win-win integration: A mitochondria targeted AIE photosensitizer for hypochlorite detection and type I & type II photodynamic therapy

Background Photodynamic therapy (PDT) is a pioneering and effective anticancer modality with low adverse effects and high selectivity. Hypochlorous acid or hypochlorite (HClO/ClO − ) is a type of inflammatory cytokine. The abnormal increase of ClO − in tumor cells is related to tumor pathogenesis and may be a “friend” for the design and synthesis of responsive phototherapy agents. However, preparing responsive phototherapy agents for all-in-one noninvasive diagnosis and simultaneous in situ therapy in a complex tumor environment is highly desirable but still remains an enormously demanding task. Results An acceptor-π bridge-donor-π bridge-acceptor (A-π-D-π-A) type photosensitizer TPTPy was designed and synthesized based on the phenothiazine structure which was used as the donor moiety as well as a ClO − responsive group. TPTPy was a multifunctional mitochondria targeted aggregation-induced emission (AIE) photosensitizer which could quickly and sensitively respond to ClO − with fluorescence “turn on” performance (19-fold fluorescence enhancement) and enhanced type I reactive oxygen species (ROS) generation to effectively ablate hypoxic tumor cells. The detection limit of TPTPy to ClO − was calculated to be 185.38 nM. The well-tailored TPTPy anchoring to mitochondria and producing ROS in situ could disrupt mitochondria and promote cell apoptosis. TPTPy was able to image inflammatory cells and tumor cells through ClO − response. In vivo results revealed that TPTPy was successfully utilized for PDT in tumor bearing nude mice and exhibited excellent biological safety for major organs. Significance and novelty A win-win integration strategy was proposed to design a tumor intracellular ClO − responsive photosensitizer TPTPy capable of both type I and type II ROS production to achieve photodynamic therapy of tumor. This work sheds light on the win-win integration design by taking full advantage of the characteristics of tumor microenvironment to build up responsive photosensitizer for in situ PDT of tumor.