An on-site colorimetric sensor for glucose in sweat based on a hydrogel embedded with GOx@Co-HHTP

, which is subsequently utilized by the peroxidase-like Co-HHTP to oxidize 3,3',5,5'-tetramethylbenzidine, thereby producing a visible color change of the hydrogel, and this phenomenon can be easily recorded using a smartphone. Under the optimized conditions, the developed system exhibits a linear response to glucose over the concentration range of 5-600 μM, with a limit of detection of 3.02 μM. The sensing system also shows high selectivity against common potential interferents. The concentration-dependent color change of the hydrogel is quantified using smartphone imaging and ImageJ-assisted gray-value analysis, enabling visual and image-assisted glucose determination. This work provides a practical strategy for constructing hydrogel-supported enzyme-nanozyme colorimetric platforms for on-site glucose monitoring.