Self-cascading nucleotide-based nanozyme for ultra-sensitive dual-signal detection of α-glucosidase activity

Designing highly sensitive method for the analysis of α-glucosidase activity is of critical value for diagnosis and therapy of diabetes. Here, we employed self-assembly of guanosine 5'-monophosphate nucleotide (GMP) with metal ions (Cu²⁺ and Tb³⁺) to prepare multifunctional Tb-CuGMP NPs. Owing to Cu²⁺-catalytic center, the as-prepared Tb-CuGMP NPs exhibits ascorbic acid oxidase (AAO)-like and peroxidase (POD)-like self-cascading catalytic activity. The AAO-POD cascade system can catalyze the oxidation of AA into dehydroascorbic acid (DHAA) with the generation of H₂O₂, which serves as a substrate for POD-like activity and catalyzed into ^•OH radicals. Based on these enzymatic reactions, a unique colorimetric detection approach in which nanozyme/TMB/AA produced oxidized TMB with characteristic blue color and DHAA sensitized Tb³⁺ to turn-on the fluorescence of the detection system was proposed. Furthermore, enzymatic hydrolysis of 2-O-a-D-glucopyranosyl-L-ascorbic acid (AA2G) into AA was coupled with AAO-POD cascade system to realize highly sensitive detection of α-glucosidase activities. Interestingly, the as-constructed dual-mode assay reduces the LOD of α-glucosidase to 5.1 × 10^-4 U/mL. To sum up, this work provides new horizon for the development of efficient multifunctional nanomaterial with integration of biocatalysis and bioassay into a single material.