A pH-Regulated Colorimetric Sensor Array for Discrimination of Biothiols Based on Two Different-Sized β-Cyclodextrin-Functionalized AuNPs

The abnormal changes of biothiols are directly related to health condition of human body, and the effective identification and quantification of biothiols is of great significance for screening and diagnosis of disease. This study described the development of a pH-regulated colorimetric sensor array for discrimination of five kinds of biothiols including cysteine (Cys), glutathione (GSH), homocysteine (Hcy), cysteamine (CA) and N-acetylcysteine (NAC). The proposed sensor array was established using 5-nm- and 20-nm-sized β -cyclodextrin-functionalized gold nanoparticles ( β -CD@AuNPs) as nonspecific receptor and signal transduction elements. Due to the different binding affinity between biothiols and β -CD@AuNPs in various pH environments, the different aggregation behaviors of nanoparticles produced unique colorimetric response patterns, which were able to be distinguished by bare eyes and UV–vis spectrophotometer. Accordingly, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed for pattern recognition and generated a clustering map for a clear differentiation of biothiols at the level of μmol/L. Furthermore, it can be proved that the method was successfully applied to the analysis of biothiols in human urine samples.