PEDOT/Superoxide Dismutase Electrode Surface Modification for Superoxide Bioelectrochemical Sensing

Abstract

An amperometric biosensor for the sensitive detection of superoxide was designed utilizing a drop-coating approach for immobilizing the superoxide dismutase enzyme on Pt electrode modified with a thin layer of poly (3,4-ethylenedioxythiophene) (PEDOT). The PEDOT layer electrodeposited on Pt was characterized by cyclic voltammetry and atomic force microscopy (AFM). Then, drop-coating procedure was chosen for the immobilization of superoxide dismutase (SOD), which was incorporated at the electrode surface using a solution containing SOD, glutaraldehyde and bovine serum albumin (optimized composition: SOD 0.1 % – BSA 2 % – GA 2.5 %.) This simple procedure allows forming a reproducible enzymatic biocomposite layer that allows optimal sensitivity and limit of detection for superoxide sensing. The synergistic effect integrates an effective conductivity and permselectivity attributed to the PEDOT layer, as well as the specificity and selectivity of SOD for the detection of superoxide. A high sensitivity (0.82±0.01 μA/μM) and a low detection limit of 11 nM were obtained, as well as good selectivity against main interfering biological compounds such as uric acid and ascorbic acid. Our results suggest that the biosensor could be used for the detection and quantification of O2- in vitro and in vivo.