Electron Transfer of Myoglobin Immobilized in Au Electrodes Modified with a RAFT PMMA-Block-PDMAEMA Polymer

Carla N Toledo,Fábio H Florenzano,José M Schneedorf

doi:10.1155/2014/184206

Abstract

Myoglobin was immobilized with poly(methyl methacrylate)-block-poly[(2-dimethylamino)ethyl methacrylate]PMMA-block-PDMAEMA polymer synthesized by reversible addition-fragmentation chain transfer technique (RAFT). Cyclic voltammograms gave direct and slow quasireversible heterogeneous electron transfer kinetics between Mb-PMMA-block-PDMAEMA modified electrode and the redox center of the protein. The values for electron rate constant (Ks) and transfer coefficient (α) were0.055±0.01·s−1and0.81±0.08, respectively. The reduction potential determined as a function of temperature (293–328 K) revealed a value of reaction center entropy ofΔS0of351.3±0.0002 J·mol−1·K−1and enthalpy change of-76.8±0.1 kJ·mol−1, suggesting solvent effects and charge ionization atmosphere involved in the reaction parallel to hydrophobic interactions with the copolymer. The immobilized protein also exhibits an electrocatalytical response to reduction of hydrogen peroxide, with an apparentKmof114.7±58.7 μM. The overall results substantiate the design and use of RAFT polymers towards the development of third-generation biosensors.

Highlights

Direct electron transfer of proteins on the surface of bare electrodes is known to present some trouble due to the deep buried of protein redox centers in its structure, as well as adsorptive denaturation and unfavorable orientations of the macromolecule [1]
As some reversible addition-fragmentation chain transfer technique (RAFT) polymers seem to exhibit electroactivity [11, 12], they would be used for entrapment of macromolecules under electrochemical investigation
The aim of this work was to investigate the redox properties of myoglobin immobilized in PMMA-block-PDMAEMA, as a feasible approach to the development of a third-generation biosensor

Summary

Introduction

Direct electron transfer of proteins on the surface of bare electrodes is known to present some trouble due to the deep buried of protein redox centers in its structure, as well as adsorptive denaturation and unfavorable orientations of the macromolecule [1]. RAFT technique uses a chain transfer compound to attain control over the molecular weight and polydispersity during a free-radical polymerization, resulting in well-defined polymers, as well as diblock, triblock, and polymers with more complex architectures [8]. RAFT polymers have attracted considerable attention in the last decade, toward to a broad spectrum of applications including optoelectronics, block copolymer therapeutics, and star polymer rheology control agents [9]. In this regard, several derivatives of diblock RAFT polymers such as poly(methyl methacrylate)block-poly[(2-dimethylamino) ethyl methacrylate](PMMAb-PDMAEMA) have been used due to their versatility, stability, and ease of processing [10]. The aim of this work was to investigate the redox properties of myoglobin immobilized in PMMA-block-PDMAEMA, as a feasible approach to the development of a third-generation biosensor

Objectives

Methods

Results