Wearable microneedle patches integrated with a bicatalytic nanozyme for self-cascade amplified dopamine sensing

This study constructs a wearable microneedle sensing platform integrated with a bicatalytic nanozyme, enabling minimally invasive detection of dopamine (DA) in interstitial fluid. Firstly, a dual-enzyme mimic nanozyme (CMCO-S) with high catechol oxidase and catalase activities was synthesized via the Mn and S co-doping strategy. It was then employed to construct a highly efficient self-oxygenating cyclic cascade sensing system. Specifically, catechol oxidase activity catalyzes the oxidation of catechol compounds in the presence of O₂, simultaneously generating H₂O₂ as an intermediate product. Subsequently, catalase activity immediately decomposes the generated H₂O₂ into O₂ and H₂O, thereby achieving self-sustaining oxygen recycling and efficient reuse. This closed-loop cascade reaction significantly enhances the catalytic efficiency and realizes effective signal amplification. Based on this cyclic system, the present study further developed a rapid and ultrasensitive dual-mode method for dopamine detection. In the presence of resorcinol, both the 478 nm fluorescence and 420 nm absorbance of the catalytic products display remarkable positive linear correlations with dopamine concentration. The two modes cover linear ranges of 0.03-100 μM and 0.1-100 μM, with limits of detection (LOD) of 0.016 μM and 0.049 μM, and the assay is completed within 5 min. By integrating this self-sustaining oxygen-driven cascade amplification sensing system into a gel microneedle patch, a visualized analysis platform capable of both extracting and detecting dopamine in skin interstitial fluid was ultimately constructed. This work provides a practically feasible strategy for developing wearable devices for dopamine detection in interstitial fluid.