Design strategies and recent advances in reversible fluorescent probes for redox

Real-time monitoring of the variation of redox is significant for the dynamic reflecting of the degree of oxidative stress in biological systems. Most of the fluorescent probes can respond to monotonically increased redox, but fail to respond to the fluctuation. Fortunately, the emergence of reversible probes overcame the above issue. Therefore, a review of the design strategies of reversible fluorescence probes for redox would help to develop advanced tools for complicated bio-microenvironments. In this review, we focused on the research progress of reversible fluorescent probes for redox in terms of response sites, including chalcogen atoms (S, Se, Te), quinones, CC bonds, and other types. In each category, we summarized the design strategies and response mechanisms: prone to fluctuated redox of chalcogen atoms; the transformation between hydroquinone and quinone; nucleophilic reaction site (CC bonds) for reactive sulfur species. Moreover, real-time monitoring of redox in cellular, zebrafish and mice was discussed. Finally, future opportunities and challenges in the clinical translation of reversible fluorescent probes, for example, low toxicity, long excitation and emission wavelengths, short response times, and high sensitivity were discussed. We hope this review may promote the development of more robust reversible fluorescent probes to further understand redox-related pathological events.