Simultaneous lancet-free monitoring of alcohol and glucose from low-volumes of perspired human sweat

A lancet-free, label-free biosensor for simultaneous detection of sweat glucose and alcohol was demonstrated using zinc oxide thin films integrated into a nanoporous flexible electrode system. Sensing was achieved from perspired human sweat at low volumes (1–3 μL), comparable to ambient conditions without external stimulation. Zinc oxide thin film electrodes were surface functionalized with alcohol oxidase enzyme and with glucose oxidase enzyme towards developing an affinity biosensor specific to the physiological relevant range of alcohol comprising of 0–2 drinks (0–50 mg/dl) and physiologically relevant range of glucose ranging from hypo- to hyper-glycaemia (50–130 mg/dl) in perspired human sweat. Sensing was achieved by measuring impedance changes associated with alcohol and glucose binding onto the sensor interface using electrochemical impedance spectroscopy with a dynamic range from 0.01–200 mg/dl and a limit of detection of 0.01 mg/dl for alcohol in human sweat. Sensor calibration in synthetic sweat containing interferents (25–200 mg/dl) and comparison using regression and Bland-Altman analysis of sweat sensor performance was done with BACtrack®. Combinatorial detection of glucose and ethanol in perspired human sweat and comparison of sweat sensor performance with Accu-Chek® blood glucose monitoring system that we expect would be relevant for pre-diabetics and diabetics for monitoring their glucose levels and alcohol consumption.