Adsorption and catalytic activity of glucose oxidase accumulated on OTCE upon the application of external potential

Abstract

This article describes the adsorption of glucose oxidase (GOx) onto optically transparent carbon electrodes (OTCE) under the effect of applied potential and the analysis of the enzymatic activity of the resulting GOx/OTCE substrates. In order to avoid electrochemical interferences with the enzyme redox center, control electrochemical experiments were performed using flavin adenine dinucleotide (FAD) and GOx/OTCE substrates. Then, the enzyme adsorption experiments were carried out as a function of the potential applied (ranged from the open circuit potential to +950 mV), the pH solution, the concentration of enzyme, and the ionic strength on the environment. The experimental results demonstrated that an increase in the adsorbed amount of GOx on the OTCE can be achieved when the potential was applied. Although the increase in the adsorbed amount was examined as a function of the potential, a maximum enzymatic activity was observed in the GOx/OTCE substrate achieved at +800 mV. These experiments suggest that although an increase in the amount of enzyme adsorbed can be obtained by the application of an external potential to the electrode, the magnitude of such potential can produce detrimental effects in the conformation of the adsorbed protein and should be carefully considered. As such, the article describes a simple and rational approach to increase the amount of enzyme adsorbed on a surface and can be applied to improve the sensitivity of a variety of biosensors.

Adsorption of Soft and Hard Proteins onto OTCEs under the Influence of an External Electric Field

“…In this regard, the adsorption of the first layer of proteins onto the OTCE (at OCP) yielded thicknesses values of 3.1 ± 0.2 nm and 6.7 ± 0.4 nm for GOx and IgG, respectively. In agreement with previous reports, 15 the corresponding thickness values are compatible with the formation of incomplete layers without a preferential side-on orientation. It is important to note that when the potential was applied, IgG exhibited a slightly higher initial adsorption rate ((2.5 ± 0.2) × 10 −2 mg·m −2 ·min −1 ) than GOx ((0.16 ± 0.04) × 10 −2 mg·m −2 ·min −1 ), suggesting that more compact proteins would be less susceptible to the potential-induced adsorption process.…”

Development and characterization of carbon based electrodes from pyrolyzed paper for biosensing applications

“…[66, 67] After adsorbing the enzyme, each electrode was transferred to the electrochemical cell containing 35 mL phosphate buffer solution (10 mmol L −1 , pH = 8.5) and the electrochemical response was recorded by chronoamperometry. Calibration curves were performed by adding known amounts of uric acid dissolved in phosphate buffer (10 mmol L −1 , pH = 8.5) and recording the resulting current (oxidation of H 2 O 2 at +650 mV).…”

Electrochemical Detection Using an Engraved Microchip – Capillary Electrophoresis Platform

“…The LOD was estimated to be 2.5 μM. These values are comparable to other sensors reported in the literature .…”