A rapid reduction of Au(I→0) strategy for the colorimetric detection and discrimination of proteins

A gold nanoparticle (AuNP)-based sensing strategy based on rapid reduction of Au(I→0) is proposed. As a proof-of-concept study, the proposed sensing principle is designed for simultaneous and colorimetric detection and discrimination of multiple proteins. In the presence of H₂O₂, the target proteins could reduce Au(I) (i.e. HAuCl₂) to AuNPs with different sizes, shapes and dispersion/aggregation states, thus resulting in rapidly colorimetric identification of different proteins. The optical response (i.e. color) of AuNPs is found to be characteristic of a given protein. The color response patterns are characteristic for each protein and can be quantitatively differentiated by statistical techniques. The sensor array is capable of discriminating proteins at concentrations as low as 0.1 μg/mL with high accuracy. A linear relationship was observed between the total Euclidean distances and protein concentration, providing the potential for protein quantification using this sensor array. The limit of detection (LOD) for catalase (Cat) is 0.08 μg/mL. The good linear range (from 0 to 8 μg/mL) has been used for the quantitative assay of Cat. To show a potentially practical application, this method was used to detect and discriminate proteins in human urine and tear samples. Graphical abstract We report a facile gold nanoparticle (AuNP)-based sensing strategy, that is, "a rapid reduction of Au(I) to Au(0) nanoparticles with different sizes and shapes by analytes that having certain reducing capabilities, resulting in different colours." The proposed sensing principle is designed for simultaneous, colorimetric detection and discrimination of multiple proteins.