Studies On Direct Electrochemistry Of Redox Proteins And Its Applications In Electrochemical Biosensing

The electrochemistry research of horseradish peroxidase (HRP) and glucose oxidase (GOD) has aroused great interest in bioelectrochemistry and biological fields, which is very important both for studying electron transfer behaviors and electrocatalytic mechanism of the enzymes, and fabricating the-third-generation biosensors. Hence, in order to achieve the direct electrochemistry of enzymes, in this paper we construct several novel composite carriers to immobilize enzymes. These novel composite materials not only provide favourable microenvironment for the enzymes, but also improve the direct electron transfer between the enzymes and the electrode. Meanwhile, enzymes immobilized in these materials exhibit outstanding electrocatalytic properties. The main work in this paper is summarized below:(1) A novel hybrid film based on theβ-cyclodextrin (β-CD) and room temprature ionic liquids (IL) was fabricated to immobilize horseradish peroxidase. Thanks to the unique character of the hybrid film, such as excellent biocompatible ability and electron conductivity, we built a novel platform to improve the direct electron transfer between HRP and the electrode, and realized the direct electrochemistry of HRP. HRP immobilized in the hybrid film retained its bioactivity, and exhibited high electrocatalytic effect towards the reduction of H2O2, as well as high affinity for quercetin.(2) Ionic liquid mixed with acetylene black (AB) was modified on the glassy carbon electrode, and the results of scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) showed that AB was successfully dispersed into IL. After glucose oxidase (GOD) was entrapped in AB/IL composite film modified on the electrode, the direct electron transfer between GOD and the electrode was realized. The cyclic voltammograms research showed that GOD immobilized in the composite film retained its biocatalytical effect towards glucose, and possible interfering species such as ascorbic acid and uric acid did not interfere with the determination of glucose.(3) An amphiphilic diblock copolymer PEG-b-PGMA was synthesised, and acetylene black can be dispersed well in the copolymer aqueous solution. Hence, we fabricated AB/PEG-b-PGMA hybrid film on the glassy carbon electrode in order to immobilize horseradish peroxidase. Since AB possesses many favourable character, such as large specific surface area, excellent electric conductivity and super capacity of accumulation, AB/PEG-b-PGMA composite film not only provide favourable microenvironment for HRP, but also improve the direct electrochemistry of HRP. HRP immobilized in the composite film retained its bioactivity, and exhibited high electrocatalytic effect towards the reduction of H2O2, as well as high affinity for N-acetyl-p-aminophen (APAP).