纳米材料修饰电极上吸附态葡萄糖氧化酶的酶活性和电活性的比较

采用石英晶体微天平(QCM)技术, 监测了裸金(Au)电极、电沉积纳米金的金电极(Au_ed/Au)、多壁碳纳米管(MWCNTs)修饰的金电极(MWCNTs/Au)以及MWCNTs 修饰后再电沉积纳米金的金电极(Au_ed/MWCNTs/Au)上葡萄糖氧化酶(GOx)的吸附过程, 测算了吸附固定的GOx质量. 通过阳极恒电位检测吸附酶与葡萄糖发生酶反应所产生的过氧化氢, 考察了这些酶电极的安培响应, 并测算了各吸附态GOx的质量比生物活性(MSBAi).也通过循环伏安法研究酶的直接电化学, 测算了各吸附态GOx的电活性百分数(EAP_i). 实验结果表明, 酶吸附量和酶电极的安培响应满足MWCNTs/Au > Au_ed/MWCNTs/Au > Au_ed/Au > Au 的顺序; MSBA_i满足Au > Au_ed/MWCNTs/Au > Au_ed/Au > MWCNTs/Au的顺序; 而EAP_i则满足MWCNTs/Au > Au_ed/MWCNTs/Au > Au_ed /Au > Au的顺序. 根据酶和纳米材料的亲疏水作用以及酶的吸附量对实验结果进行了合理解释, 也定量验证了电极上吸附酶分子的总生物活性与酶电极的安培响应呈正相关关系, 所得数据和结论有助于纳米材料固定酶及其安培酶电极的研究.

Comparison of Enzymatic Activities and Electroactivities of Adsorbed Glucose Oxidase on Several Nanomaterial-Modified Electrodes

The quartz-crystal microbalance technique was used to monitor the adsorption of glucose oxidase (GOx) on bare Au, Au-electrodeposited Au (Au_ed/Au), multiwalled carbon nanotube (MWCNT)- modified Au (MWCNTs/Au), and Au-electrodeposited MWCNT-modified Au (Au_ed/MWCNTs/Au) electrodes. The mass of GOx at saturated adsorption was obtained in each case. The amperometric responses of these enzyme electrodes were examined, and the mass-specific bioactivities of the immobilized (adsorbed) GOx (MSBA_i) were evaluated through anodic potentiostatic detection of enzymatically generated H₂O₂ in the presence of glucose. The direct electrochemistry of adsorbed GOx was studied by cyclic voltammetry, to obtain the electroactivity percentage of the immobilized (adsorbed) GOx (EAP_i) in each case. We found that the amounts of enzyme adsorbed and the amperometric responses of these enzyme electrodes follow the order MWCNTs/Au > Au_ed/MWCNTs/Au > Au_ed/Au > Au; MSBA_i follows the order of Au > Au_ed/MWCNTs/Au > Au_ed/Au > MWCNTs/Au; and EAP_i follows the order of MWCNTs/Au > Au_ed/MWCNTs/Au > Au_ed/Au > Au. The experimental data are interpreted based on hydrophobic/hydrophilic interactions among enzyme molecules and the nanomaterials, as well as the amount of adsorbed GOx. It was also verified that the total enzymatic activity of all the electrode-adsorbed enzyme molecules is positively related to the amperometric responses of the enzyme electrodes. This work is useful in studying the immobilization of enzyme on nanomaterials and thus-prepared amperometric enzyme electrodes.