Calcium Fluoride/Manganese Dioxide Nanocomposite with Dual Enzyme-like Activities for Uric Acid Sensing: A Comparative Study of Enzyme and Nonenzyme Methods.

The debate over enzyme methods versus nonenzyme methods in the field of nanosensing has lasted for decades despite hundreds of published studies on this topic. In this study, we first present a comparative analysis of these methods using a reaction based on the CaF 2 /MnO 2 nanocomposite (CM Nc) with dual-enzyme activity, presenting oxidase- and peroxidase-like activities. Uric acid (UA) is a byproduct of purine metabolism in the body, and abnormal levels can cause many diseases; hence, tracking the amount of UA in human serum is crucial. The enzyme method was established using uricase and CM Nc: UA produced H 2 O 2 when catalyzed by uricase; H 2 O 2 was then catalyzed into reactive oxygen species (ROS) by the peroxidase activity of the CM Nc; this ROS oxidized 3,3',5,5'-tetramethylbenzidine (TMB), which was oxidized into blue oxidized TMB (oxTMB). The nonenzyme method was built on the scavenging effect of UA on the ROS, which prevented the catalytic capability of CM Nc toward TMB and induced blue oxTMB fading. The results of further tests revealed the good selectivity of the enzyme method compared to the fast response of the nonenzyme method. Additionally, both methods were effective in determining the UA concentration in human serum. The two separate methods can also independently verify each other, increasing the accuracy of the detection results in accordance with the relatively independent detection principles. This research provided theoretical backing for the practical design of multienzyme nanozyme catalysts, which can facilitate the precise detection of UA in biochemical products.