A near-infrared excitation/emission fluorescent probe for imaging of endogenous cysteine in living cells and zebrafish

The fluorescence imaging technique provides an essential tool for studying biological systems. However, due to the interference of autofluorescence of biological tissues, the application of short-wavelength fluorescent probes in biological imaging was limited. The near-infrared (NIR) excitation/emission fluorescent probe possesses unique advantages in optical imaging in vivo, including less light scattering, minimal photo-damage to biological samples, deep tissue penetration, and weak autofluorescence interference from complicated biological systems. In this work, a convenient fluorophore ( E )-2-[2-(6-hydroxy-2,3-dihydro-1 H -xanthen-4-yl)vinyl]-3- methylbenzo[ d ]thiazol-3-ium iodide ( DXM-OH ) with NIR excitation and emission was rationally designed and developed. What’s more, DXM-OH was applied to construct an “OFF-ON” fluorescent probe ( E )-2-{2-[6-(acryloyloxy)-2,3-dihydro-1 H - xanthen-4-yl]vinyl}-3-methylbenzo[ d ]thiazol-3-ium iodide ( DXM ) for sensitive and selective detection of cysteine (Cys). The experimental results showed that DXM had the advantages of good cell permeability, low toxicity, and excellent optical properties (NIR excitation/emission) and it was successfully applied to image Cys of living cells and zebrafish.