A fluorescence and colorimetric dual-mode sensing system for Cys/Hcy detection

Accurate detection of Cys/Hcy levels is critical for evaluating human health conditions. In this study, we developed an innovative fluorescence/colorimetric dual-mode sensing system to detect Cys/Hcy by dynamically adjusting the level of oxTMB. The system utilizes Au@PtNPs with peroxidase-like activity to catalyze the oxidation of colorless 3,3,5,5- tetramethylbenzidine (TMB) to blue oxTMB, and TAPB@DMTP COF, a fluorescent nanomaterial with abundant spatial pores, could be used as a carrier for oxTMB, and the two were made fluorescence quenching due to the fluorescence inner filter effect. The addition of Cys/Hcy allowed the originally dispersed Au@PtNPs to aggregate to inhibit their peroxidase-like activity, thus indirectly regulating the oxTMB content. At this point, the absorbance signal decreased and fluorescence was restored. To this end, we have developed a special fluorescence/colorimetric dual-mode sensing system for the detection of Cys/Hcy. The detection limits of the fluorescence and colorimetric methods for Cys/Hcy were determined to be 0.788 nM (Cys), 0.663 nM (Hcy), and 1.795 nM (Cys), 1.886 nM (Hcy), respectively. The sensing system was also evaluated for its ability to withstand interferences from 12 anions and 13 amino acids, demonstrating excellent unti-interference and selectivity. The recoveries of the two methods for detecting Cys/Hcy in fetal bovine serum were found to be 98.9%-114.3% with RSDs as low as 0.52% (fluorescence) and 0.92% (colorimetric), respectively.