Fluorescence turn-on and colorimetric dual readout assay of glutathione over cysteine based on the fluorescence inner-filter effect of oxidized TMB on TMPyP

Quantitative fluorescence turn-on and colorimetric detection of glutathione (GSH) with rapid speed, low cost have attained much attention. Herein, we developed a sensitive fluorescence turn-on and colorimetric sensor for GSH based on the inner-filter effect (IFE), which is the first time to select oxTMB and TMPyP as the IFE absorber and fluorophore pair, respectively. The absorption band of oxTMB matches well with the emission band of TMPyP in the IFE-based fluorescent assay. In the absence of GSH, the absorption peak of oxTMB at 652 nm significantly overlaps with the emission of TMPyP, resulting in the efficient IFE and inhibition of the fluorescence of TMPyP. In the presence of GSH, the absorption intensity at 652 nm decreases, generating the recovery of the fluorescence of TMPyP. Therefore, this approach is demonstrated to be a novel candidate for detection of GSH, with high sensitivity and selectivity. The linear dynamic range for the concentrations of GSH is between 0.1 μM to 20 μM along with a limit of detection (LOD) of about 30 nM (calculated LOD as 3σ/slope). Finally, this novel sensor was successfully applied for GSH detection in fetal calf serum, and satisfactory recovery was achieved.