Emission enhancement of fluorescent glutathione-capped gold nanoclusters by cerium (III) ion-induced aggregation for sensitive detecting α-glucosidase in human serum using ratiometric fluorometry

A fluorescence probe was designed based on carbon dots (CDs) and glutathione-capped gold nanoclusters (GSH-AuNCs) for detecting α-glucosidase in human serum. By employing L-ascorbic acid-2-O-α-D-glucopyranosyl (AAG) as substrate for the α-glucosidase catalyzed hydrolysis reaction, ascorbic acid (AA) was generated, and subsequently reduced cerium (IV) ion (Ce⁴⁺) to Ce³⁺. Since Ce³⁺ would selectively improve the aggregation of GSH-AuNCs, the consequent aggregation-induced emission enhancement (AIEE) of aggregated GSH-AuNCs was measured for indicating the activity of α-glucosidase involved in the hydrolysis process. To furtherly improve the precision of spectral response, ratiometric fluorometry was realized by taking the fluorescence emission of CDs, which was affected insignificantly during the above process, as the fluorescence reference. The developed probe exhibited a linear response to α-glucosidase activity in the range of 0.01 ∼ 0.1 U‧mL⁻¹, with a limit of detection (LOD) of 0.0055 U‧mL⁻¹. Results of serum sample examination and cellular imaging reveal the promising potential of the developed probe for clinical diagnosis.