Well-regulated synthesis of conductive polymer by bipolar electrochemistry: an effective substrate for enzyme immobilization toward oxygen reduction reaction

Optimizing the electrical connection between enzymes and electrodes surface is critical in the development of biosensors, enzymatic biofuel cells, and other bioelectrocatalytic applications. There are some limitation to achieve those aims, therefore introducing of suitable support for enzyme immobilization was used to overcome this limitation [1]. A variety of materials including metals, alloys, inorganic substances polymers and composites are used to modify the surface of electrodes for enzyme attachment. Conducting polymers (CPs) based on the macromolecular systems have been used for many application areas such as electrochromic devices, energy storage, and biotechnology in material science. In view of their attractive properties, CPs are promising candidates for biomolecule immobilization in biosensing and biofuel cell systems [2]. Electrochemically synthesis of polymer films is a suitable way for adjusting the surface of electrodes to produce functionalized CPs with enhanced controlling the film thickness and morphology even at a micro /nanoscale substrate [3]. Bipolar electrochemistry (BPE) has been recently explored for the modification of various conductive substrates. The BPE features particular advantages compared to conventional electrochemistry especially in a simple setup, which involve one direct current (DC) power supply, low cost, ease of setup, no direct electrical connection is required and many electrodes can be controlled simultaneously with a single DC power supply [4]. Here we report the electropolymerization of 3-thiophenecarboxcylic acid on the suitable support such as Au by bipolar electrochemistry method, which provide polymer functional groups on surface of the support. The synthesized polymer film on the Au support shows preferable substrate for 235 immobilization of bilirubin oxidase enzyme. The resulting polymer films were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy. The prepared bioelectrodes as novel system were characterized by voltammetric techniques such as cyclic voltammetry in order to investigate its electrocatalytic activity for oxygen reduction reaction (ORR) and calculate kinetics parameters. The onset potential and the magnitude of current density for oxygen reduction on the modified electrode were 0.55 V (vs. Ag/AgCl) and 967 μA cm-2, respectively. Furthermore, the electrocatalytic performance of the proposed system toward ORR was better than the immobilized bilirubin oxidase enzyme on synthesized poly -3-thiophenecarboxcylic by conventional three-electrode system.