Development of near-infrared xanthene fluorescence probe for the highly selective and sensitive detection of cysteine

Abnormal levels of the biological thiol cysteine (Cys) have been shown to be associated with growth retardation, skin lesions, and neurotoxicity in humans. In order to fully elucidate the role of Cys in biological systems, its levels must be monitored through in vitro assays as well as in living cells and animals. Herein, we designed and synthesized a novel near-infrared xanthene fluorescence probe (NOF1) with an acrylate group as a trigger moiety to detect Cys over homocysteine and glutathione. The NOF1 probe exhibited a good selectivity and a high sensitivity toward Cys, with a detection limit of 210 nM. Additionally, NOF1 retained good sensitivity and selectivity in human plasma, with a good recovery of Cys within the range 98%–102%. Importantly, the NOF1 probe was successfully applied to the fluorescence imaging of Cys in living cells, zebrafish, and mice, showing great potential for applications involving the detection of Cys both in vitro and in vivo.