Covalent Modification Of Protein At Diamond And Glassy Carbon Surfaces And Electrochemical Biosensing Application

As a most widely-used biofunctional reagent for immobilization in the field of electrochemical biosensor, biomacromolecules, such as protein, enzyme and et al, are involved in metabolism and other important physiological processes which are characteristics of electron transfer. So there must be advantage for electrochemistry method to be adopted for the investigation of the electron-transfer processes of protein and enzyme. Moreover, the investigation of the direct electrochemistry of protein can help us comprehend the dynamic and thermodynamic properties of protein, establish a solid foundation to explore the biological oxidation and reduction processes, and be vitally significant for the theoretical and applicational research of new-generation biosensors, biological fuel batteries and et al. However, due to the huge dimension of bio-macromolecules' structure, their bio-active centre is usually buried deeply inside the bio-macromolecules, which must cause difficulty in the realization of the direct electrochemistry of the bio-macromolecules, such as protein or enzyme. On the other hand, carbon electrode has been broadly adopted as a kind of substrate material for the investigation of electrochemical biosensors. There are many good properties of carbon electrodes, such as perfect biological affinity, stable morphology, high chemical and electrochemical stability, good machining property, low background current and et al. Besides, due to carbon crystal's unique property and carbon materials' conjugate structure of p bond, the surface modification of carbon material can be achieved more easily. And especially, a lot of attentions have been paid for the investigation of Boron-Doped Diamond Film Electrode (BDD) which is a kind of new material with many perfect and unique properties. Despite the unique chemical and electrochemical inertness of BDD causes difficulty in its surface modification, the investigation of BDD for developing biosensors has just been carried out.In this paper, the surface pre-modification of Glassy Carbon Electrode (GC) and BDD electrode has been studied with a method named the electrochemical reduction of aromatic diazonium salts. The results show that the film monolayer of aromatic molecules covalently modified at the electrodes has an apparent blocking effect on the electron-transfer process of the redox system, Fe(CN)₆^3-/4- It was found that comparing with the R_ct value of GC or BDD electrode, the R_ct values of GC or BDD electrode covalently modified with aromatic molecules increased apparently. More than that, BDD electrode's R_ct value was found to be more than GC electrode's R_ct value, and the R_ct value of aromatic molecules-modified BDD electrode more than the one of aromatic molecules-modified GC electrode. So it indicates that the electron-transfer process of Fe(CN)₆^3-/4- at BDD electrode or aromatic molecules-modified BDD electrode is correspondingly slower than at GC electrode or aromatic molecules-modified GC electrode.With the characterization results obtained from the electrodes modified under different conditions of electrochemical reduction of aromatic molecules, the R_ct...