Multi-colorful ratio fluorescent biosensing of β-glucosidase activity based on the rapidly synthetic gold nanoclusters

Given the undeniable importance of robust analysis of β-glucosidase (β-GLU) activity in clinical diagnosis and therapeutics applications, in this work, a multi-colorful ratio fluorescent assay for monitoring β-GLU activity by applying gold nanoclusters (AuNCs) as the probes was proposed. The AuNCs were prepared via a convenient chemical reduction procedure within 15 min at 70 °C. In the catalytic system of enzymatic substrate 3-indoxyl-β-D-glucopyranoside (IDG) and β-GLU, the generations of hydrogen peroxide (H2O2) and fluorescent indoxyl oxidation product (op-ID) were demonstrated. The generated op-ID exhibited a fluorescence emission peak at 478 nm, and H2O2 quenched the fluorescence of AuNCs at 645 nm, forming a typical ratio fluorescence and multiple fluorescence color change responses to β-GLU. The ratio sensing platform determined β-GLU activity with a limit of detection (LOD) as low as 0.051 U/L. Further, β-GLU activity could also be detected in real human serum samples using the prepared biosensor. This sensing strategy was also used to construct a simple and low-cost hydrogel kit for portable monitoring of β-GLU activity, holding great potential for point-of-care testing of β-GLU-related clinical investigation.