Improving stability of biosensor based on covalent immobilization of horseradish peroxidase by γ-aminobutyric acid and application in detection of H2O2

A novel electrochemical biosensor for the determination of hydrogen peroxide (H2O2) has been fabricated through covalently immobilized horseradish peroxidase (HRP) on modified multi walled carbon nanotube (MWCNT) by gamma-aminobutyric acid (GABA) on glassy carbon electrode. Using the electrochemical techniques, the electrochemical properties of the biosensor were specified. Cyclic voltammograms of the enzyme film at pH = 7.0 exhibited a pair of quasi-reversible redox peaks according to Fe(III/II) redox process of HRP. The biosensor exhibited good efficiency for finding H2O2 with a broad linear range from 2.0 x 10(-7) M to 2.81 x 10(-4) M and a detection limit of 0.13 mu M. The surface coverage of active HRP, heterogeneous electron transfer rate constant and Michaelis-Menten constant of immobilized HRP were obtained 3.029 x 10(-9) mol cm(-2), 1.11 s(-1), and 0.23 mM respectively. Similarly, the applicability of the suggested biosensor was examined by detecting H2O2 in human plasma samples and the average recovery was obtained as 100.50 +/- 025. Moreover, the constructed biosensor presented a high stability, reproducibility and repeatability. Finally using docking and the molecular dynamics calculations, it was determined that GABA interacts with lysine residue and it causes HRP to be placed on the electrode with a specific orientation. (C) 2019 Elsevier B.V. All rights reserved.