Ratiometric Fluorescent Probe for Homocysteine and Cysteine Based on the Aldehyde Functionalized Coumarin and Successful Bioimaging Application

Novel reactive probes (C1 and C2) towards homocysteine/cysteine (Hcy/Cys) were designed and synthesized, based on the unique nucleophilic nature of bio-thiols. In the presence of Hcy/Cys, probe Cl displayed remarkable fluorescence enhancement. Meanwhile, ratiometric fluorescent probe C2 was designed through subtle structure adjustment. Differently, compound C2 displayed dramatic blue-shift in both fluorescence (100 nm) and absorption (95 mn) spectra upon the addition of Hcy/Cys. By virtue of the specific nucleophilic reaction, probe C2 had outstanding selectivity towards Hcy over Cys, GSH and other amino acids. The detection limit of probe C2 was calculated to be as low as 2.8 x 10(-7) mol/L. Moreover, C2 was successfully applied to microscopic imaging for the detection of Hcv in HeLa cells with ratiometric fluorescent methods.