Acrylamide-Coumarin-Benzaldehyde as a Turn-on Fluorescent Probe Providing an Enhanced Water Solubility for Detection of Cysteine and Homocysteine

We presented an acrylamide conjugated coumarin (1) as a fluorescent probe for detection of cysteine (Cys) and homocysteine (Hcy). Probe 1 is composed of coumarin as a fluorophore, acrylamide as a reactive site to Cys/Hcy, and benzaldehyde for improvement of the water solubility. To Cys/Hcy, the acrylamide group of 1 readily undergoes Michael addition resulting in a strong fluorescence at 420 nm through an inhibition of photo-induced electron transfer (PET). The turn-on fluorescence change of 1 was observed for Cys and Hcy, but not seen for other biologically abundant thiols (e.g., glutathione, H2S), reactive oxygen and nitrogen species, anions, and metal ions. Moreover, 1 can give strong fluorescence upon the addition of Cys and Hcy in wide pH range and their limits of detection for Cys and Hcy turned out to be 17.25 and 8.69 mu M, respectively.