Screen-printed, biocompatible and ultrasensitive sensor for real-time reactive oxygen species detection in human sweat

Excessive or burst generation of reactive oxygen species (ROS) can induce oxidative stress, precipitating a range of critical illnesses, including cancers, Parkinson's disease and Ischemia-reperfusion injury. Conventional biological assays for ROS, involving discrete steps of capturing, labelling, and spectrometric detection, are complex and time-intensive. Moreover, their accuracy is substantially compromised by the short lifespan (microseconds to milliseconds) of ROS. Consequently, there is a pressing need for a rapid and efficient method that enables real-time detection. In this study, we have developed a printable, flexible ROS sensor based on a robust nanoenzyme composite by direct deposition of the paste onto a flexible polyethylene terephthalate (PET) substrate. This device demonstrated the fast and real-time responses to the hydrogen peroxide (mimetic agent) in the laboratory and to total ROS in sweat of an individual, exhibiting an outstanding current response to hydrogen peroxide across a broad concentration range of 0.01-10 mM, with a limit of detection (LOD) of 1.85 μM. The device's sensitivity to hydrogen peroxide (136.59 μA mM^-1 cm^-2), was found to be 1.5 to 10 times higher than that of sensors previously reported. Moreover, the IFRS device successfully identified instantaneous ROS levels in the sweat of adult males in vitro, with amperometric response increased 8 times after half an hour strenuous exercise, thereby exhibiting excellent selectivity, remarkable stability, and confirmed high biosafety. Overall, the IFRS provides a viable and practical solution for simple, expedited, and real-time ROS detection in the near future.