Lancet-free and label-free diagnostics of glucose in sweat using Zinc Oxide based flexible bioelectronics

We demonstrate a wearable, flexible electrochemical biosensor for the combinatorial label-free detection of glucose in human sweat. The novel device comprises of stacked metal/metal-oxide (gold/zinc oxide) thin films within porous polyamide substrates for low-volume ultrasensitive impedance based detection of glucose and cortisol using non-faradaic electron-ionic charge transfer. In this work, we report the detection of glucose over a concentration range from 0.01–200 mg/dL spiked in synthetic and human sweat. Monoclonal antibodies specific to glucose oxidase were immobilized on thiolated ZnO sensing electrode surfaces resulting in the modulation of charge transfer within the electrical double layer (EDL). Non-Faradaic electrochemical impedance spectroscopy (EIS) was used to calibrate the sensor response with varying dose concentration through measurement of change in impedance. Reliable limit of detection (LOD) of 0.1 mg/dL in human sweat was demonstrated. Correlation of the sensor response with that of a commercial glucose meter TRUEresult™ Sensor (LOD of 20 mg/dL in blood) was found to be 0.9. Combinatorial detection of glucose and cortisol was demonstrated through frequency specific EIS measurements. Sensor variability was found to be within 15% of individual dynamic range for each molecule.