Nanoflower-structured MnO₂/Au composites with enhanced catalytic performance for colorimetric assay of α-glucosidase

α-Glucosidase (α-Glu) is an essential hydrolase that catalyzes the final step of carbohydrate digestion, playing a central role in glucose metabolism. Abnormal α-Glu activity is closely associated with type II diabetes, obesity, and Alzheimer's disease, making its precise monitoring critical for disease diagnosis and therapeutic evaluation. However, conventional detection methods often depend on natural enzymes or sophisticated nanomaterials, which face challenges of high cost, instability, and complicated operation. Thus, developing a simple, robust, and cost-effective strategy for sensitive α-Glu detection is of great significance.

In this study, a simple, low-cost, and sensitive colorimetric assay for α-Glu activity was developed based on nanozyme catalysis. Flower-like MnO₂/Au composites were synthesized via a mild and facile method, exhibiting remarkable oxidase-like activity. The MnO₂/Au nanozyme could efficiently catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by dissolved oxygen, producing a distinct blue color as the initial signal. In the presence of α-Glu, its substrate α-arbutin was hydrolyzed to generate hydroquinone, a strong reductant that rapidly reduced oxidized TMB (blue) to its colorless form, resulting in a visible signal decrease. This "color-on/color-off" mechanism enabled sensitive α-Glu detection without the need for natural enzymes or additional oxidants. The method demonstrated a low detection limit (0.005 U/mL), wide linear range, and excellent reproducibility. Recovery experiments in spiked human serum showed satisfactory results (97.7-103.2 %), confirming the robustness of the assay in complex biological matrices.

Compared with conventional methods, the proposed nanozyme-based strategy integrates ease of synthesis, mild reaction conditions, and cost-effectiveness with reliable analytical performance, highlighting its potential for rapid clinical screening and inhibitor discovery. This work not only expands the application of MnO₂-based nanozymes in biosensing but also provides a versatile platform for detecting hydrolytic enzyme activity through product-triggered signal modulation.