A Wearable Biosensor Based on Bienzyme Gel-Membrane for Sweat Lactate Monitoring by Mounting on Eyeglasses

A new enzymatic biosensor worn on eyeglasses has been developed for low-noise and noninvasive determination of lactate in human sweat during physical exercise. The Os (osmium)-complex, the electron mediator between the enzyme and the electrode, was first immobilized on a flexibly printed carbon electrode. Then, a gel membrane with the stereoscopic reticular structure of lactate oxidase and horseradish peroxidase was casted on the electrode to form the biosensor. Linearity of the biosensor was observed for up to 25 mM lactate in a phosphate buffered solution of pH 7.0. Chemical selectivity was evaluated by adding common interferent species such as ascorbic acid, glucose and uric acid to the lactate. The negligible current interference indicated excellent discriminatory selectivity of the biosensor. Applied to an analysis of the real sweat lactate dynamics of healthy subjects during cycling exercise, the amperometric profiles of the biosensors reflected changes in sweat lactate that depended on physical exercise intensity. Compared with other reported epidermal biosensors attached to the arm or leg, our biosensor not only exhibited a similar current change tendency but also rarely suffered from deformational interference due to their forehead measurement position. Such a successful application of real-time monitoring of sweat lactate means that eyeglass-bound biosensors hold considerable promise in the physical exercise and biomedical fields.