Colorimetric/fluorescence cross-validation-based carbon dot nanozyme smart sensor array for biothiols identification

Biothiols play a crucial role in maintaining redox homeostasis and signal transduction within cells, with disruptions in their levels and types linked to various diseases. Therefore, a reliable and accurate sensing platform for the identification and quantification of biothiols is of great significance for early disease diagnosis. To overcome the limitation of conventional nanozyme sensor arrays that rely solely on enzyme-like activity for biothiol identification, this study achieved a synergistic balance between the fluorescence and peroxidase-like (POD) activity of iron-doped carbon dots (Fe-CDs) by modulating endogenous iron in the precursor. Biothiols with different reducing capacities exerted distinct inhibitory effects on the POD-like activity of Fe-CDs.Meanwhile, the difference in the binding affinity between the thiol group (-SH) of diverse biothiols and Fe-CDs could be reflected by the degree of fluorescence quenching of Fe-CDs. Based on the findings, a colorimetric/fluorescence/ cross-validation sensor array based on the POD-like activity and fluorescence property of Fe-CDs was proposed for biothiol recognition. This array enabled the accurate identification of 10 types of biothiols and their mixtures. Additionally, a machine learning-assisted classification-regression model was established for the quantitative analysis of biothiols. Finally, the proposed method was successfully applied to the recognition and quantification of biothiols in serum matrix, with detection recoveries ranging from 95% to 104%. Moreover, it also achieved the differentiation between cancer cells and normal cells. This work lays a foundation for rationally designing carbon dot nanozymes with high enzyme-like activity and favorable fluorescence, while providing a reliable tool for early disease diagnosis.