A novel dual-mode sensing strategy for the determination of 1,4-dithiothreitol based on tannic acid stabilized copper nanocluster

In this paper, a novel sensing strategy with both ratiometric fluorescence and colorimetric responses towards 1,4-dithiothreitol (DTT) was developed based on tannic acid-templated copper nanoclusters (TA-CuNCs). The one-step reduction approach was utilized to obtain TA-CuNCs with the fluorescence emission peak located at 436 nm. Through the catalytic oxidation of Cu2+, o-phenylenediamine (OPD) could be converted to 2,3-diaminophenazine (DAP) with an obvious fluorescence signal at 557 nm. Additionally, the obtained yellow DAP showed a clear absorption peak at 420 nm, DAP could cause a significant fluorescence quenching of TA-CuNCs on account of inner-filter effect (IFE). The oxidation process between Cu2+ and OPD could be largely prevented by 1,4-dithiothreitol (DTT), whose sulfhydryl groups bound to Cu2+, and the fluorescence intensity of DAP was diminished, whereas the fluorescence of the TA-CuNCs was restored. The ratiometric fluorescence signal and absorbance intensity changed with the concentration of DTT in the linear ranges of 5–45 μM and 5–40 μM, respectively. And the limits of detection (LOD) for two modes were found to be 2.98 and 2.03 μM, respectively. Furthermore, the dual-mode assay method was used for the determination of DTT accurately and reliably in human serum samples.