Click chemistry in the design of AIEgens for biosensing and bioimaging

The development of rapid,selective,and sensitivefluorescent sensors is essential for visualizing and quantifying biological molecules and processes in vitro,ex vitro,and in vivo,which is important for not only fundamental biological studies but the accurate diagnosis of diseases.The emergingfield of activity-based sensing(ABS),a sensing method that utilizes molecular reactivity for analyte detection possesses many advantages including high specificity,sensitivity and accuracy.The aggrega-tion caused quenching phenomenon which occurs in most conventionalfluorophores results in reduced labeling efficiency of the target analytes and low photobleaching resistance,therefore limiting the applications of the ABS strategy.In contrast,aggre-gation induced emission(AIE)active luminogens(AIEgens)provide exceptional molecular frameworks for ABS.Of the many reaction classes utilized in the AIEgen ABS approach,click chemistry has become increasing popular.In this review,the sensing concepts of the ABS approach with AIEgens and the principles of click chemistry are discussed,followed by a systematic summary of the application of specific click chemistry reactions in AIEgen ABS protocols for the detection of an array of target analytes.Furthermore,the utility of click chemistry in the construction of AIEgens for bioimaging will also be showcased throughout the review.