Study On The Biosensors Based On Hydroxyapatite And Carbon Nanotube Composite

Biosensors have been extensively attracted and used due to their unique advantages. Recently, many materials have been used to develop the biosensors. However, much attention has been paid to modify electrode with carbon nanotubes and other nano-materials. How to improve the performances of biosensors, such as the high sensitivity, excellent stability and the quick response time were also focused.Because of good biological compatibility and bioactivity, the hydroxyapatite (HA) is not only used in clinical instead of the bone substitute, but also used in the basic research of bioelectrochemistry and the development of biosensors.Based on the electrochemical deposition technique of HA which has studied in our group, the glucose oxidase (GOD), hemoglobin and other biological macromolecules were immobilized on the surface of glassy carbon electrode modified by electrodeposited HA. The immolization of GOD on the electrode modified by HA and carbon nanotubes (CNTs) composite were also studied. The electrochemical behaviors of different modified electrodes have been investigated. This work provided references of research and experimental techniques for developing the new biosensors. This paper includes the following aspects:1. The study on the glucose sensor based on hydroxyapatite modified electrodeThe coatings of HA have been electrodeposited on the surface of GC electrodes with double potential step technique. Then GOD has been immobilized onto the HA/GC electrodes, and the GOD-HA/GC electrode has been fabricated. The cyclic voltammetry (CV) measurement showed that a pair of well-defined reduction and oxidation peaks was obtained. The ratio of peak current is closed to 1.The formal potential E0'is -0.387V and ?Ep is 28 mV. This experiment result proved that the direct electron transfer of GOD immobilized on HA modified GC electrode has been promoted. The electron transfer reaction is a quasi-reversible process controlled by adsorption. The modified electrode can be used for determination of glucose.2. The study on the glucose sensor based on hydroxyapatite and carbon nanotube composite modified electrodeA novel glucose oxidase sensor based on HA and single-wall carbon nanotube SWNTs composite has been developed for the detection of glucose. At first, the hydroxyapatite was electrodeposited onto the surface of GC electrode coated by single-wall carbon nanotubes (SWNTs), then GOD was immobilized by self assembled method. The direct electron transfer mechanism of GOD immobilized on HA/SWNTs/GC electrode was discussed with the measurement results of electrochemical impedance spectroscopy (EIS) and its electrochemical parameters. The results showed that HA cooperated with SWNTs can promote the electron transfer reaction. The effect of different pH on electrochemical behavior of modified electrode was also discussed. The response to different concentrations of glucose was investigated with differential pulse voltammetry (DPV). The GOD-HA/SWNTs/GC electrode exhibited a good linear response to glucose.3. Study on electrochemical behavior of Hemoglobin immobilized on GC electrode modified by hydroxyapatite and carbon nanotube and its applicationThe hydroxyapatite was electrodeposited onto the single-wall carbon nanotubes modified GC electrod. Hb is immobilized on the surface of HA/SWNTs/GC electrode by layer-by-layer method. The different dispersants for dispersed SWNTs have been tested.The result showed that the SWNTs which is dispersed by DMF is better than that by Chitosan. The cyclic voltammetry results shows that the direct electron transfer of Hb at modified electrode was observed, that is a quasi-reversible reaction controlled by the adsorption. The modified electrode also has a linear response to different concentrations of H₂O₂.