Wearable transdermal colorimetric microneedle patch for Uric acid monitoring based on peroxidase-like polypyrrole nanoparticles

Regular Uric Acid (UA) monitoring is essential for patients with gout, and great efforts have been made to develop portable, low-cost and easy-to-operate UA detection technologies. Herein, we developed a wearable microneedle colorimetric patch integrating the sampling function and the capability of real-time UA analysis in a minimally invasive manner, which can dramatically improve patient compliance. For the operation of the constructed device, the poly(vinyl alcohol) based microneedle was embedded with the uricase which catalyzed the oxidation of UA extracted from the interstitial fluids and produced H2O2. Polypyrrole nanoparticles (PPy NPs) with peroxidase-like activity encapsulated in the display layer triggered the reaction between H2O2 and 3,3',5,5'- tetramethylbenzidine, resulting in the color variation associated with the concentration of H2O2 produced by the UA oxidation. Thus, the UA level can be determined with the naked eye. According to the relationship between the color intensity and the UA concentration, the UA level within the range of 200-1000 μM can be further quantified accurately by analyzing sample images with a smart phone. The developed device exhibited good selectivity and stability, and a limit of detection of about 65 μM. This wearable device holds great potential in health management and clinical point-of-care detection.