Mitochondria-targeted fluorescent probe for rapid detection of thiols and its application in bioimaging

Biothiols are crucial reactive sulfur species in living cells, playing an essential role in maintaining the normal function of organisms. Effective detection of biothiols promotes the exploration of metabolic pathways and physiological functions of organisms. In this paper, a cyanine-based, mitochondria-targetable fluorescent probe, Cy-DNBS, was designed and synthesized. This probe uses a lipophilic cation unit as mitochondrial targeting site and DNBS group as the fluorescence quencher as well as the recognition site. The probe shows a distinct fluorescence emission at 604 nm upon rapid interaction with intracellular biothiols, owing to the removal of the 2,4-dinitrobenzene-sulfonyl (DNBS) group and the blockage of PET process. Moreover, the probe can not only image endogenous thiols, but also efficiently target mitochondria and evaluate thiol fluctuations under mitochondrial oxidative stress induced by H2O2. Collectively, the new low cytotoxic probe can serve as a promising tool for monitoring cellular thiols and further exploring elevant disease processes.