AIEgen for cancer discrimination

Cancer is one of the most severe diseases and is challenging human health and longevity. Cancer diagnosis is extremely important to improve the survival rate of patients. Cancer tissues/cells have been characterized with four distinctive biological features that significantly differ from normal tissues/cells, including higher vascular permeability, specific microenvironments of acidic pH, high reducibility and hypoxia, higher mitochondrial membrane potential, and overexpressed proteins. Therefore, accurate cancer discrimination can be achieved by targeting these characteristics. Currently, various imaging modalities have been developed to discriminate cancerous tissues/cells. Amongst, fluorescent technology has dominated the central position because it can directly, in-situ and real-time visualize and distinguish cancer tissues/cells at nano-micrometer resolution. Since its first discovery in 2001, aggregation-induced emission (AIE) has developed as a promissing and powerful fluorescent technique. Fluorogens with AIE characteristics (AIEgens) are non-emissive in molecular state, but show enhanced emission in aggregated state due to its restriction of intramolecular motion. Besides, AIEgens can work at high concentrations without considering the aggregation-caused quenching effect encountered by conventional organic fluorescent dyes. Given their unique superiorities, AIE-based fluorescent imaging technologies have emerged as appealing alternatives to traditional ones and obtained wide-ranging uses in cancer discrimination. Thus, herein we provide a comprehensive review of the recent progress of AIEgen-based fluorescent probes for cancer discrimination. These fluorescent probes can be classified into four categories, corresponding to four characteristics of cancer. The design strategies and working mechanisms for these probes and their applications for cancer bioimaging were highlighted and the pros and cons of these probes were criticized. Ultimately, this review will end with the discussion of future development of AIEgen-based cancer discrimination.