Wash-free detection and bioimaging by AIEgens

Wash-free fluorescence detection and bioimaging has attracted increasing attention as it can largely simplify the analytical procedure, significantly shorten the detection time, and effectively avoid the possible interference and the analyte loss caused by the washing step. The development of fluorescent probes with wash-free signal switches is thus much desired. Fluorogens with aggregation-induced emission characteristics (AIEgens) are non-emissive when dissolved in solution, but exhibit strong emission in the aggregated state, thus providing a great opportunity for the design and construction of wash-free fluorescence technologies by directly manipulating the intramolecular motion. In this review, we will discuss the latest progress of AIEgens for application in wash-free detection and bioimaging by presenting several seminal examples of environmental monitoring, food safety inspection, clinical diagnostics, cellular microenvironmental monitoring, organelle imaging, in vivo visualization and microbial detection. The design strategies and responsive mechanisms of AIEgens for wash-free signal switches will be highlighted, and the current challenges and further directions in this field will be elaborated and discussed.