Water-Based Conductive Ink Formulations for Enzyme-Based Wearable Biosensors

Herein, this work reports the first example of second-generation wearable biosensor arrays based on a printed electrode technology involving a water-based graphite ink, for the simultaneous detection of l-lactate and d-glucose. The water-based graphite ink is deposited onto a flexible polyethylene terephthalate sheet, namely stencil-printed graphite (SPG) electrodes, and further modified with [Os(bpy)2(Cl)(PVI)10] as an osmium redox polymer to shuttle the electrons from the redox center of lactate oxidase from Aerococcus viridans (LOx) and gluocose oxidase from Aspergillus niger (GOx). The proposed biosensor array exhibits a limit of detection as low as (9.0 +/- 1.0) x 10-6 m for LOx/SPG-[Os(bpy)2(Cl)(PVI)10] and (3.0 +/- 0.5) x 10-6 m for GOx/SPG-[Os(bpy)2(Cl)(PVI)10], a sensitivity as high as 1.32 mu A mm-1 for LOx/SPG-[Os(bpy)2(Cl)(PVI)10] and 28.4 mu A mm-1 for GOx/SPG-[Os(bpy)2(Cl)(PVI)10]. The technology is also selective when tested in buffer and artificial sweat and is endowed with an operational/storage stability of approximate to 80% of the initial signal retained after 20 days. Finally, the proposed array is integrated in a wristband and successfully tested for the continuous monitoring of l-lactate and d-glucose in a healthy volunteer during daily activity. This is foreseen as a real-time wearable device for sport-medicine and healthcare applications. The proposed biosensor array based on water-based conductive inks exhibits a limit of detection as low as (9.0 +/- 1.0) x 10-6 m for lactate and (3.0 +/- 0.5) x 10-6 m for glucose. The array is successfully integrated in a rubber wristband tested in sweat. image