Gold nanoclusters-based dual-channel assay for colorimetric and turn-on fluorescent sensing of alkaline phosphatase

Here, based on their bifunctional peroxidase-mimicking activity and fluorescence of bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs), we develop a colorimetric and fluorescent dual-channel assay for alkaline phosphatase activity determination. The peroxidase-like activity of BSA-AuNCs makes it possible to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into its blue product (oxTMB) in the presence of H2O2, and result in the fluorescence quench of BSA-AuNCs simultaneously due to the inner filter effect between oxTMB and BSA-AuNCs. While the ascorbic acid generating form alkaline phosphatase (ALP)-catalyzed hydrolysis of L-ascorbic acid-2-phosphate can inhibit the oxidation of TMB, thereby inducing decolorization of oxTMB and fluorescence recovery of BSA-AuNCs. Based on these findings, a dual-readout assay for ALP activity sensing using BSA-AuNCs has been reported for the first time. The detection limitation can reach as low as 0.26 and 0.16 mU mL-1 by colorimetric and fluorescent method, respectively. Moreover, the developed assay has been successfully applied to detect ALP in human serum samples with satisfactory results. This method may not only offer new idea for simple, sensitive and accurate detection of ALP activity, but also broaden the applications of BSA-AuNCs in bioanalysis.