MnO2 nanoparticles as tandem nano-enzyme for colorimetric flexible sensor in sweat

The emergence of flexible, painless sensors for biomolecule measurement represents a growing trend in biomedical research. In this context, a highly sensitive flexible sweat sensor, incorporating MnO2-TMB@PAM aggregates employing dual-detection routes via visualization and UV–vis spectrometry, has been developed. The sensor utilizes bovine serum albumin (BSA) templated MnO2 nanoparticles (NPs) as a catalyst for glucose detection. Unlike natural enzymes, this nanozyme is not only cost-effective and stable but also exhibits tandem enzyme-like activities, which facilitates quick and straightforward glucose detection. MnO2 NPs are synthesized in situ on the surface of polyacrylamide (PAM), ensuring high stability and increasing the contact area of reactors, thereby enhancing the catalytic efficiency of MnO2 NPs. Additionally, 3,3′,5,5′-tetramethylbenzidine (TMB) is modified on the hydrogel to create an integrated sensing patch (referred to as MnO2-TMB@PAM). This patch enables fast and convenient sensing routes, positioning it as a potential candidate for point-of-care testing (POCT) devices. Due to the excellent flexibility and transmittance of PAM, the sensing patch allows for rapid colorimetric analysis of biomolecules such as glucose and dopamine via UV–vis spectrophotometry, as well as visual detection with the naked eyes. Consequently, a high-sensitive, selective, and visually active flexible sensor has been established based on colorimetric and visual methods, facilitating efficient sensing of biomarkers from in vitro biological fluids.