Enzyme‐Free Detection of Glucose with a Hybrid Conductive Gel Electrode

Abstract

Current assays for glucose monitoring rely predominantly on glucose oxidation-catalyzing enzymes because of the high specificity of enzyme-substrate interactions. Enzymes are however expensive, suffer from instability during fabrication, operation and storage, and necessitate complex procedures for integration with transducer materials. These challenges, rendering the enzyme-based sensors disadvantageous for routine glucose monitoring, can be overcome by non-enzymatic sensors. Here, for the enzyme-free detection of glucose, an electroactive gel is developed via one-pot polymerization. The functional material is a hybrid of the conducting polymer poly(3,4-ethylenedioxythiophene):polystyrenesulfonate and a polyacrylamide gel functionalized with phenylboronic acid. As an electrode, the gel exhibits a specific current response to glucose within the standard concentration range measured in the complex bloodlike medium. When integrated as the lateral, micrometer-scale gate electrode of an organic electrochemical transistor (OECT), the channel current is proven to be sensitive to the presence of glucose in the measurement solution. The advantage of the OECT based sensor compared to the amperometric electrode is its miniaturized form, amplified input signal as well the elimination of a reference electrode. Adaptable to different geometries, this conducting gel exhibits multifunctionality within its soft, gel-like architecture, that is, mixed ionic and electronic conductivity and glucose specific electrical response. 2 IntroductionGlucose is the primary nutrient of living systems to perform a variety of cellular metabolic processes including cellular respiration and biosynthesis. [1,2] In case of malfunction, cells may end up not taking up glucose sufficiently, which leads to abnormal levels of glucose build up in the bloodstream. The high concentration of glucose in blood is typically associated with the disease, diabetes. Diabetes is a pandemic disorder which was one of the top ten leading causes of death worldwide in 2015 and it is predicted to become the tenth most burdensome disease by 2030. [3][4][5] A good part of diabetes treatment as well as its early diagnosis involve self-monitoring of the amount of glucose in biological fluids. Thus, powerful, low-cost and easy-to-use glucose sensors are on high demand.The inherent specificity and electrochemical reversibility of enzymes poise them as the biorecognition element of choice for a wide range of metabolites. The majority of current glucose sensors are thus electronic and based on the redox enzyme, glucose oxidase that undergoes redox reactions with the analyte, glucose. In these platforms, the enzyme transforms glucose into gluconolactone and hydrogen peroxide (H2O2). H2O2 reacts with a metal electrode in its vicinity, resulting in a change in the flow of electrical current which is directly proportional to concentration of glucose that has reacted with the enzyme. The electrical potential required to oxidize H2O2 however matches that for the oxidation of several ...

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