Immobilization of glucose oxidase on plasma-treated polyethylene for non-invasive glucose detection

Glucose oxidase (GOx) has been covalently immobilized onto plasma-treated low-density polyethylene (PTLDPE) deposited by solvent-casting onto a glassy carbon electrode. PT-LDPE acts as a very simple and cheap mediator between the enzyme and the conducting substrate, the resulting electrode (GOx/PT-LDPE/GC) being able to detect effectively glucose under conditions of pH and temperature that mimic those of sweat. Glucose has been successfully monitored using GOx/PT-LDPE/GC electrodes via both, chronoamperometric and voltammetric measurements. The lowest limit of detection (LOD) was obtained with electrodes prepared with a GOx concentration of 5 mg/mL. This represents a significant reduction in the amount of enzyme as compared to electrodes obtained by dropping GOx onto PT-LDPE/GC (non-covalent immobilization), in which the required enzyme concentration was 33 mg/mL. Furthermore, the LOD has been decreased two orders of magnitude, from 1.3 mM for sensors without covalent immobilization to less than 0.05 mM. It is worth noting that the latter value is fully compatible with glucose concentration in sweat, which ranges from 0.06 to 0.11 mM for healthy patients and from 0.01 to 1 mM in diabetic patients. Moreover, the developed sensor is able to promote the reduction of hydrogen peroxide produced during the oxidation of glucose to gluconolactone.

Automated summary

Glucose oxidase was covalently immobilized onto plasma-treated low-density polyethylene to prepare an electrode for effective glucose detection under conditions mimicking sweat. The use of covalent immobilization significantly reduced enzyme usage and lowered the detection limit by two orders of magnitude compared to non-covalent methods.