The studies on the adsorption behavior of glucose oxidase and its effect on the characteristics of glucose sensors

• Main Authors: Ke-HsuanWang, 王可瑄
• Other Authors: Yuh-Lang Lee
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/51227706894780366208

博士 === 國立成功大學 === 化學工程學系碩博士班 === 100 === The adsorption behavior of glucose oxidase (GOx) from aqueous solution to the air/liquid interface was studied. The GOx monolayer at the air/liquid was transferred on the surstrate for application to glucose sensor. With the variation of surface pressure in the adsorption stage (π-t), pressure-area (π-A) isotherms, hysteresis curves, and the Brewster angle microscopy (BAM), the GOx adsorption and the interaction between GOx and Langmuir monolayer were elucidated. The morphology of GOx LB films was also examined by the observation of atomic force microscopy (AFM). The GOx secondary structure and the GOx amount were examined by a circular dichroism (CD) spectroscopy and Fourier transform infrared spectroscopy (FTIR). Amperometric measurements were made for determining the performance of assembled glucose sensors. The adsorption of GOx from aqueous solution to an air/liquid interface can be classified into two stages according to the surface pressure variation. In the first adsorption stage, GOx adsorb as a single-molecular layer, extended by the interface-molecule interaction, and organize as a mainly β-sheet conformation. The second adsorption stage is initiated by further adsorption of GOx into the interface, pushing up the pre-adsorbed proteins away from the interface, forming GOx multilayer, and inducing a conformational transition into α-helix. The glucose sensing experiments demonstrate that GOx with α-helix conformation has a much higher electroacivity than the β-sheet. The electrostatic attractive interaction between octadecylamine (ODA) and GOx not only enchance the amount of adsorbed GOx, but also promote the uniformity of ODA and GOx to avoid the reduction in GOx catalytic ability. It is possible to prepare an immobilized enzyme film with condensed and homogeneous phase by surface-film compression. Overall, the {AuNPs-1/GOxAuNPs-2} sensor prepared by layer-by-layer deposition with a close-packed AuNP monolayer and the GOx/AuNPs monolayer exhibited the highest current sensitivity (0.521 μA•cm-2•mM-1) and the fastest response time (within 12 s).