Stable Chitosan and Prussian Blue-Coated Laser-Induced Graphene Skin Sensor for the Electrochemical Detection of Hydrogen Peroxide in Sweat

Developing a noninvasive skin peroxide monitoring technology is highly desirable for managing a number of metabolic disorders associated with diabetes, pulmonary diseases, or other health conditions. To date, the majority of studies on peroxide detection have been conducted on simulated sweat and high pH conditions, which are beyond the physiological range, in order to provide an enhanced response. Here, a skin-worn amperometric sensor, based on laser-induced graphene (LIG), surface-engineered with a Prussian blue (PB)–chitosan (CS) network was fabricated by one-step electrodeposition for the stable and sensitive detection of H2O2 in human eccrine perspiration. The hybrid (PB–CS) network and laser-written electrode configuration were optimized through systematic investigation of electrodeposition parameters and concurrent feedback from electrochemical and morphological characterization at each fabrication step. Different from the multitude of carbon-based electrodes functionalized with metallic nanoparticles reported in the literature, the sensor was operated at a low potential of −0.036 V vs Ag/AgCl in unmodified human eccrine perspiration. The low working potential ensured that the sensor is highly specific, immune to the current from oxygen reduction or common interfering species, whereas the inclusion of CS in the hybrid coating afforded a highly stable performance over a period of 14 days. The sensor was able to monitor H2O2 over the linear range of 10–1000 μM with a low detection limit of 6.31 μM and achieved a recovery of 98.73% (%RSD 0.86) in human eccrine perspiration. This facile biosensor based on directly laser-written electrodes coupled with the one-step PB–CS fabrication strategy has the potential to form the basis for the development of oxidase enzyme-based sensors in sweat.