Enzyme-Free Glucose Monitoring Patch

Abstract

Monitoring of glucose levels in non-invasive biofluids, such as saliva and sweat, can advance personal health tracking. However, the approach remains challenging due to the low glucose concentration in saliva and sweat, about 100 times lower than in the blood. Commercial glucose sensors rely on glucose oxidase to measure blood glucose levels with enzyme reactions. The enzyme activity varies with pH, oxygen level, and temperature (more than 40ºC). Also, the method often suffers from cross-reactivity with other sugar molecules, such as maltose and xylose [1]. Thus, it is crucial to develop highly sensitive and stable non-enzymatic sensors for detecting glucose in non-invasive biological fluids.In this work, we present an enzyme-free, reagent-free electrochemical glucose monitoring patch based on a glucose imprinted polymer nanocomposite. The nanocomposite comprises redox-active chitosan-ferrocene (Cs-Fc) wrapped multi-walled carbon nanotubes (MWCNTs). The Cs-Fc is a polymer with covalently secured redox-active ferrocene, effectively preventing the out leakage of redox substances [2]. The incorporation of MWCNTs increases the surface area, conductivity, and electron transfer rate. The glucose imprinted layer was grown on the surface of the nanocomposite by electropolymerization of functional monomers o-phenylenediamine (o-PD) and 3-aminophenylboronic acid (APBA) in the presence of glucose templates. The successful removal of template molecules created glucose specific recognition sites in the polymer matrices. The sensor directly detected the presence of glucose upon their binding into these cavities. The electrochemical property of the modified sensor was characterized by cyclic voltammetry (CV) in a potential range of 0-0.5 V at a scan rate of 100 mVs-1 in 1x PBS (pH 7.4) solution. For glucose sensing, the sensor was immersed in a sample solution containing different glucose concentrations for 30 min. We have optimized the composition ratio and assay conditions for sensitive glucose detection. Preliminary results indicated a change in redox peak current of ~2.7 times relative to the control upon adding 1 mM glucose, as shown in Figure 1. The proposed glucose patch is label-free, reagentless, cost-effective, easy fabrication, and expected to be utilized for sensitive and selective glucose detection from sweat.