Recent Advances in Fluorescent Probes based on Different Recognition Motifs for Biothiols

Fluorescent probes are useful tools for viewing living biothiols but the structural similarities between Cys, Hcy, and GSH complicate their selective selection. This review presents a systematic overview of fluorescent probes for biothiols organized by chemical recognition motifs used in their design. The probes are classified into three main groups according to the responsive sites: nucleophilic addition sites (acrylates, maleimides and unsaturated ketones), nucleophilic substitution sites (e.g. ester bonds, disulfides and nitrobenzoxadiazole (NBD)) and metal coordination or redox sites (e.g. Cu 2+ /Hg 2+ centers and Selenium ethers). Recognition mechanisms (addition-cyclization cascades, SNAr reactions, metal displacement) are summarized. Biomedical applications of these probes (subcellular organelle imaging, in vivo disease monitoring, and theranostic platforms) are summarized. Finally, current challenges and future perspectives, particularly regarding near-infrared II (NIR-II) imaging and artificial intelligence-assisted design, are briefly outlined.