Abstract:
Cysteine (Cys) is a crucial biomolecule involved in protein synthesis, antioxidant defense, and cellular signaling, while H2S serves as a gasotransmitter. The imbalance of these thiols is linked to a range of pathological conditions, highlighting the need for precise and reliable detection methods. Herein, we have developed a bright far-red fluorescent probe (BYN-DNS) for the selective and sensitive detection of Cys and H2S. The probe is synthesized using methoxy-1-naphthaldehyde modified BODIPY molecule (BYN-OH) functionalized with a 2,4-dinitrobenzene sulfonyl (DNS) moiety. The probe produces very low fluorescence due to ICT between the DNS group and the BYN-OH derivative. In the presence of Cys and H2S, the DNS group cleaved by nucleophilic substitution reaction, releasing the far-red fluorophore BYN-OH and resulting in an 81- and 122 fold increase in fluorescence at 610 nm, respectively. The probe exhibits significant selectivity for Cys and H2S compared to structurally similar thiol, including homocysteine (Hcy) and glutathione (GSH). The detection limits were calculated to be 85 nM for Cys and 68 nM for H2S. The quantum yield of the probe in the presence of H2S was calculated to be 0.63. The practical applicability and biocompatibility of BYN-DNS were confirmed via human blood serum analysis and live-cell fluorescence imaging.