A NIR fluorescent probe with large Stoke-shift based on cyanine for specifically imaging Cys in mitochondria

Cysteine (Cys) is a sulfhydryl-containing essential amino acid that can maintain redox balance in organisms. Abnormal changes in Cys levels can damage mitochondria, which are the main source of reactive oxygen species in cells. Therefore, there is an urgent need for a tool that can recognize Cys specifically in the mitochondria. In this study, a fluorescent probe (CRF-NIR) for the detection of Cys was designed and synthesized based on cyanine dye. The probe showed a NIR fluorescence emission at 752 nm and large Stokes shift (137 nm) after treated with Cys. The detecting process could complete within 30 min in MeOH/PBS buffer (4/1, v/v) solution and displayed a low limit of detection (LOD) as 0.22 μM. The sensing mechanism was checked by ESI-MS and the DFT calculations. More importantly, the probe had been shown to have good mitochondria-targeting and high-contrast imaging abilities, which has the potential to become a new chemical tool and provide help for detecting Cys in living systems. © 2024 Elsevier B.V.