A New Glucose Biosensor Based on Sandwich Configuration of Organically Modified Sol-Gel Glass

Abstract

A new glucose biosensor was developed based on the sandwich configuration of organically modified sol-gel glasses. The new sol-gel glass was developed using 3-aminopropyltrimethoxy silane and 2-(3,4-epoxycyclohexyl)-ethyltrimethoxy silane. Two types of sol-gel glasses were used to develop glucose biosensors that differ in absence (A) and the presence of graphite powder [particle size 1–2 μ] (B). An additional additive (polyethylene glycol, Mol. wt. 6000) was also incorporated in both types of the upper sol-gel glass layer. The new sol-gel matrix with immobilized glucose oxidase was analyzed by scanning electron microscopy (SEM).The sandwich configuration was developed using a bilayer of sol-gel glasses having a layer of glucose oxidase in between the bilayer. This electrode with special configuration was used to form a layer of sol-gel glass of ca. 0.2 mm thickness. The performance of sol-gel glasses (A & B) was analyzed based on cyclic voltammetry using ferrocene monocarboxylic acid. The results show a diffusion limited condition of ferrocene across the sol-gel matrix. The characterization of sol-gel glass based biosensor was recorded based on the cyclic voltammograms in absence and presence of glucose. The results show an increase in anodic current which is also characteristic of hydrogen peroxide oxidation in both cases (A & B). The responses of the sol-gel glasses based biosensors were analyzed based on chronoamperometric measurements. An amplified signal on the addition of the same concentrations of glucose was recorded with the B-type sol-gel glass electrode which was attributed to its relatively high porosity and better conductivity of the graphite loaded sol-gel glass. These observations were in accordance with the results on the diffusion of ferrocene and the magnitude of anodic current resulting from hydrogen peroxide oxidation. The calibration plots for glucose analysis using both type of sensors are reported. Data on the mediated electrochemical oxidation of glucose oxidase using soluble ferrocene were also reported based on cyclic voltammograms and amperometric measurement.