Progress and trends of photodynamic therapy: from traditional photosensitizers to AIE-based photosensitizers.

Photodynamic therapy (PDT) is an established clinical treatment technology with which utilizes excitation light of a specific wavelength to excite photosensitizers (PSs) for generating reactive oxygen species (ROS) which lead to the cancer cell death. Over the past decades of PDT research, apparent progress have been made in the development of PSs. However, many inherent characteristics of traditional PSs have caused many various problems in PDT, such as low treatment efficiency at aggregation state and shallow treatment depth. In allusion to these problems, aggregation-induced emission (AIE)-based PSs have been reported in recent years. Here, the article reviews the design strategy and the biomedical applications of AIE PSs in detail, which begins with a summary of traditional PSs for a comparison between traditional PSs and AIE PSs. Subsequently, the different functional AIE PSs in photodynamic cancer cells ablation and image-guided therapy are discussed in detail taking controllable excitation wavelength, stimulus response and PDT/photothermal therapy synergistic effect as examples. These studies have demonstrated the great potential of AIE PSs as effective theranostic agents in recent years. And the review provides references for the development of new PSs and hopefully spur more research interest in AIE PSs for future research.