Direct Electrochemistry of Redox Proteins and Enzymes Promoted by Carbon Nanotubes

Yajing Yin,Yafen Lü,Chenxin Cai,Ping Wu

doi:10.3390/s5040220

Abstract

The redox protein and enzyme, such as hemoglobin (Hb), horseradish peroxidase(HRP) and glucose oxidase (GOx), was immobilized on the surface of the carbon nanotubemodified glassy carbon (CNT/GC) electrode, respectively. The cyclic voltammetric resultsindicated that the redox protein and enzyme underwent effective and stable direct electrontransfer reaction with a pair of nearly symmetrical redox peaks. The formal redox potential,E0’, was almost independent on the scan rates, the average value of E0’ for Hb, HRP andGOx was –0.343 ± 0.001, –0.319 ± 0.002 and –0.456 ± 0.0008 V (vs. SCE，pH 6.9),respectively. The dependence of E0’ on the pH solution indicated that the direct electrontransfer of Hb and HRP was a one-electron-transfer reaction process coupled with oneproton-transfer, while the GOx was a two-electron-transfer coupled with two-protontransfer.The apparent heterogeneous electron transfer rate constant (ks) was 1.25 ± 0.25,2.07 ± 0.69 and 1.74 ± 0.42 s-1 for Hb, HRP and GOx, respectively. The method presentedhere can be easily extended to immobilize other redox enzymes or proteins and obtain theirdirect electrochemistry.

Highlights

Electron transfer in biological systems is one of the leading areas of biochemical and biophysical sciences, and has been received more and more attention [1,2,3,4,5,6,7,8,9]
We report the direct electron transfer of hemoglobin (Hb), horseradish peroxidase (HRP) and glucose oxidase (GOx), which was immobilized onto the surface of carbon nanotubes (CNT), respectively
When CNT were sonicated with CTAB solution, the CTAB molecule was adsorbed on the surface of CNT and created a distribution of positive charges that prevented the CNT aggregation and induced its suspension in water to form a stable black suspension

Summary

Introduction

Electron transfer in biological systems is one of the leading areas of biochemical and biophysical sciences, and has been received more and more attention [1,2,3,4,5,6,7,8,9]. Enzyme-modified electrodes provide a basis for constructing biosensors, biomedical devices and enzymatic bioreactors From these studies, one can find potential applications in biotechnology. If an enzyme immobilized on an electrode surface is capable of the direct electron transfer and keeping its bioactivity, it can be used in biosensors and biofuel cells without the addition of mediators or promoters onto the electrode surface or into the solution. It is difficult for an enzyme (a protein) to carry out the direct electrochemical reaction due to several factors. The suitable electrode materials and immobilization methods of enzymes (proteins) onto the electrode surface are important for obtaining their direct electrochemical reaction and keeping their bioactivities

Objectives

Results

Conclusion