Highly selective colorimetric and fluorescent BODIPY dyes for sensing of cysteine and/or homocysteine

Abstract

By taking advantage of “turn off” or “turn on” fluorescence of visible light excitable BODIPYs, a selective fluorescent and colorimetric “naked eye” sensing of cysteine (Cys) and/or homocysteine (Hcy) in methanol-HEPES buffer (45 mM, pH = 7.2, v/v = 1/1) solution over various common amino acids and related thiol-containing compounds has been achieved based on the reaction of the formyl groups on α- and β-formyl BODIPYs 1 and 3 with Cys/Hcy. β-FormylBODIPY 1 showed a selective response for both Cys and Hcy over the other analytes, with an apparent color change from green to light brown due to a dramatic quenching of the fluorescence intensity. In contrast, α-formylBODIPY 3 gave “naked eye” discrimination between Cys and Hcy, with a dramatic color change from light orange to yellowish green because of a significant increase of the green fluorescence intensity with the addition of Cys. The possible mechanism for sensing of Cys and/or Hcy by BODIPYs 1 and 3 was studied by NMR, HRMS and DFT calculations. α-FormylBODIPY 3 has been applied to the biological imaging of Cys in living cells.