Preparation of an aptamer-based photoelectrochemical sensor for sequential detection of both mercury and glutathione in commercial skin lightening cosmetics.

Glutathione (GSH) and Hg2+ both possess skin-lightening effects, but GSH is a beneficial component while Hg2+ poses significant health risks to humans. Accurate quantification of both GSH and Hg2+ is crucial for distinguishing the quality of commercial skin lightening cosmetics. In this study, the In2S3-Ti3C2 photoelectric material was synthesized and modified onto the surface of FTO. By incorporating T-rich Hg2+ aptamer DNA with ferrocene-modified termini (Apt-Fc) onto the material surface, a photoelectrochemical (PEC) aptamer sensor was developed for the sequential detection of Hg2+ and glutathione (GSH) using the same sensing platform. In the absence of Hg2+, Fc acts as an electron acceptor to competitively capture photogenerated electrons from In2S3-Ti3C2, reducing the number of electrons transferred to the electrode and resulting in a decreased photocurrent. Upon Hg2+ addition, the formed T-Hg2+-T structure brings Fc into closer proximity to the photoelectrode surface, where the steric hindrance effect of the T-Hg2+-T duplex and the competitive electron-capturing effect of Fc synergistically lead to a further decreased photocurrent, enabling sensitive Hg2+ detection. On the other hand, GSH reduces MnO2 to Mn2+, which accelerates the CRISPR/Cas12a cleavage activity to randomly cleave the T-Hg2+-T chain; the resultant enhanced photocurrent enables GSH detection. The detection limits are 8.47 × 10-12 mol L-1 and 4.83 × 10-11 mol L-1 for Hg2+ and GSH, respectively. The sensor has been successfully applied to the sequential detection of illegally added Hg2+ and the endogenous antioxidant GSH in commercial skin lightening cosmetics.