The impact of immobilization process on the electrochemical performance, bioactivity and conformation of glucose oxidase enzyme

Our research focuses on the electrochemical performance and influence of conformation on the bioactivity of glucose oxidase (GOx) immobilized on 4-(pyrrole-1-yl) benzoic acid (PyBA) modified multiwalled carbon nanotubes (MWCNT). The presence of PyBA in the nanostructured network introduces carboxylic groups participating in the enzyme immobilization on the electrode surface. In order to study the influence of GOx immobilization process the crosslinking and covalent binding has been applied. The electrochemical characteristics of both GOx modified electrodes were investigated by voltammetric, amperometric and potentiostatic methods. The electronic transfer properties of immobilized enzyme onto MWCNT/PyBA were monitored by electrochemical impedance spectroscopy (EIS). FTIR spectroscopy was used to explore how the immobilization process affected conformational changes in the structure of GOx. The electrochemical measurements revealed that for crosslinked enzyme the heterogeneous electron transfer (ET) rate constant ks was calculated to be 3.2 s−1 and confirmed by spectroscopic investigation on the structure of enzyme. A great number of unordered structures in the GOx immobilized by covalent binding, which were not found in the native and crosslinked GOx, indicate that there is a definite change in the tertiary structure of the protein. Such change suggests a partial denaturation of the enzyme molecule and definitely lower ks = 0.4 s−1. The distinct features of the bioelectrocatalytic systems were the long stability, reproducibility, repeatability and ability to reject or minimize most interferents. These observations provide a promising platform for the development of biofuel cells and biosensing devices.