Study On The Electrochemical Behaviors Of Biological Molecule At The Electrode Modified With Hydroxyapatite

Direct electrochemistry of redox proteins has been a hot object in biological chemical fields. Researches on direct electrochemistry of the proteins/enzymes can be used to extract essential physicochemical data concerning the thermodynamics and kinetics information, provide mechanism of electron exchanges among proteins/ enzymes in biological system. Moreover, it can establish a foundation for fabricating new kinds of biosensors. But usually it is difficult to achieve the direct electron transfer between the proteins and electrodes,mainly because the electroactive centers are embedded in the non-conducting polypeptides.The hydroxyapatite coating as the bone substitute, has good biological compatibility and bioactivity, it is also non-toxic,harmless and non-carcinogenesis to human body. By now it has been put into clinical use as the human body skeleton substitution material. On the basis of the previous research work of our lab, the PAMAM/HA composition coatings have been deposited on the electrodes by continuous potential step method, to study the electrochemical behaviors of the biological molecule such as cytochrome c (Cyt.c), glucoseoxidase (GOD), haemachrome (Hb).The coating of PAMAM/HA deposited on Pt electrodes have been prepared by double potential step. The CV results show a pair of well-defined redox peaks, the ratio of anodic and cathodic peak current is 1:1, the formal potential is about 0. 018 V (vs. SCE) and peak potential separationΔEp is 70 mV, all of which demonstrate that it was a quasi-reversible process controlled by diffusion, and the electron transfer of Cyt.c can be promoted by HA.The experiment results show that the the electron transfer Cyt.c can be affected by different conditions of electrodeposition. On the basis of impedance spectra (EIS) and electrochemistry parameter fitting, the possible electron transfer mechanism of Cyt.c promoted by PAMAM/HA coating is also discussed. The results show that the direct electron transfer of Cyt.c will be much better if the time of deposition is increased.The coatings of HA are deposited on GC electrodes with double potential step. The glucose oxidase (GOD) is immobilized onto the HA/GC electrodes and fixed by Nafion to form GOD-HA/GC electrode. The CV results show that a pair of nealy reversible redox peaks are observed due to the direct electron transfer of GOD on the HA/GC electrodes. The experiment show that GOD modified on HA/GC electrodes can keep its biological and electrocatalysis activity. The effects of different pH and temperature on the respond current of the modified electrode have been discussed.The GC electrode modified with HA coatings is prepared by double potential step. The hemoglobin (Hb) is immobilized onto the HA/GC electrodes and fixed by Nafion solution, called as Hb-HA/GC electrode. The UV-Vis and FTIR spectroscopy demonstrate that the Hb modified on the HA/GC electrodes can keep its original secondary structure. The CV results show that Hb doesn't denaturalize as its electrochemical behaviors can be observed. It was a quasi-reversible process controlled by surface. Besides, it can catalyse O₂ and H₂O₂ efficiently, it also can be used to detect NO^2-.