【作者】 王展；

【导师】 赵元弟；

【作者基本信息】 华中科技大学 ， 生物医学工程， 2009， 博士

【摘要】 生物分子参与完成生命体中的新陈代谢等许多生理过程，在这些生命过程中很多生物分子都要经历电子转移过程。从一定意义上讲，研究生命过程实质上就是研究生物体中的电子传递过程。电化学方法用来研究生物分子的电子传递过程有着特别的优势，不仅可以测定其基本的热力学和动力学参数，而且可以揭示生物体系中电子转移机理，对于制备电化学生物传感器以满足生物医学、环境检测和工业快速分析的需要具有重要意义。纳米材料具有独特的物理和化学特性，能促进生物分子的活性中心与电极间的直接电子交换，同时最大限度地保持生物分子的活性。因此，将纳米技术应用于生物分子电化学分析研究，有利于创新性地建立一些新理论、新技术和新方法，是一个很有前景的领域。本论文利用CdTe和CdSe纳米颗粒（量子点，QD）以及铂纳米颗粒作为修饰材料，构建了一系列新型生物传感器，并对其电化学性质进行了研究。主要研究结果如下：（1）将水溶性CdTe纳米颗粒和血红蛋白（Hb）混合修饰在玻碳（GC）电极表面，并用Nafion将其固定，制备了稳定的Nafion／Hb-CdTe／GC电极。利用循环伏安（CV）法和安培法详细研究Hb的直接电化学行为和对H₂O₂的催化动力学过程。实验表明，利用CdTe纳米颗粒可实现Hb的直接电化学，促进Hb与电极之间的电子传递，电子转移速率常数κ为0．068 s^-1，传递系数α为0．59。同时，表面固定的Hb仍然保持对H₂O₂的催化活性，其表观米氏常数为17．7μM。修饰后的电极可用于检测H₂O₂，其线性检测范围为5．0×10^-6～4．5×10^-5M，检测限为8．4×10^-7M（S／N=3）。修饰电极具有较高的灵敏度，并具有较好的重现性和稳定性。（2）采用多种方式将脂溶性CdSe／ZnS量子点与辣根过氧化物酶（HRP）共同修饰到GC电极表面，实验表明，只有当脂溶性量子点以蒸发沉积的方式修饰时，HRP在该修饰电极上才能发生明显的直接电子传递，电子传递速率常数为5．80±0．70s^-1。紫外和红外光谱表明HRP在此电极表面的构象没有发生明显变化。进一步研究表明，此修饰电极对H₂O₂有良好的催化活性，其表观米氏常数为0．152 mM。修饰后的电极可用于检测H₂O₂，其线性检测范围为5．0×10^-6～1．0×10^-4 M，检测限为2．84×10^-7M，且具有良好的可重复性和稳定性。这说明核壳结构的量子点可以实现蛋白质与电极的直接电子传递，且这一电化学行为与量子点在电极表面的修饰方式直接相关。（3）采用不同的手段对脂溶性CdSe／ZnS量子点在HRP表面的蒸发沉积进行表征，研究了沉积时间和沉积温度对HRP催化活性影响。确定了量子点的蒸发沉积的最佳条件，并对该条件下制备的修饰电极的电化学行为进行了详细的研究。结果表明，量子点于35℃下沉积7 hr对HRP的直接电子传递有很好的促进作用。在此条件下，量子点和HRP在电极表面的覆盖量分别为5．56×10^-8mol cm^-2和6．47×10^-11molcm^-2，HRP的的电子传递速率为6．01 s^-1。（4）在负载有巯基丙酸修饰CdTe纳米颗粒的半胱氨酸（Cys）自组装修饰电极上固定了Trametes versicolor漆酶，利用循环伏安法和安培法研究了它的直接电化学行为和对抗坏血酸（AA）的催化动力学过程，发现漆酶在CdTe纳米颗粒存在情况下可与电极发生直接电子传递，电子传递速率常数κ为21．7 s^-1，传递系数α为0．47。固定的漆酶保持对AA的催化活性，其表观米氏常数为0．47 mM。修饰后的电极可以用来检测溶液中的AA，其线性检测范围为1．0×10^-5～1．4×10^-4 M，检测限为1．4×10^-6M（S／N=3），且具有较好的灵敏性、可重复性和稳定性。（5）使用循环伏安电沉积的方法，在铂盘电极上均匀地沉积了铂纳米颗粒。结果表明，该方法制备的铂纳米颗粒修饰铂电极（PNP／Pt）对水杨酸（SA）有良好的电催化氧化能力，可以在弱碱环境下检测SA，对SA的响应电流是修饰前的9．2倍，其线性检测范围为2．0×10^-5～5．0×10^-44 M，并具有高的重复性和稳定性，能可靠地应用于SA的检测。更多还原

【Abstract】 Biomolecules play important role in metabolism and other important physiologicalproeesses, which are charaeteristics of electron transfer between their oxidation andreduction states. Therefore, to study the proeess of life is to investigate the electrontransmition in essence. Electrochemical methods are applied widely in life scienceresearches to research the electron transfer process among the biomolecules, which notonly can obtain the basic thermodynamics and dynamics parameters, and show theelectron transfer mechanism as well. This is significant to understand the life process, andprepare the electrochemical biosensors to meet the needs of the biomedical, environmentaltest and rapid analysis of industrial.Due to their special physical and chemical properties, nanosturctured materials canactivate while active electrode surface, and promote the direct electron transfer betweenthe active center in biomolecule and the electrode surface. Therefore, the application ofNano-technology on electrochemical analysis of biological molecules is a promising aera.and conducive to the establishment of some new theories, new technologies and newmethods.In this thesis, some novel biosensors were constructed based on CdTe quantum dot（QD）, CdSe QD and Platinum nanoparticle, and the electrochemical properties andcatalytic effects were studied. The main contents and results are summarized as follows:（1） Water-soluble CdTe nanoparticles and hemoglobin （Hb） were immobilized on aglassy carbon （GC） electrode with Nafion. The direct electrochemistry and the catalytickinetics of Hb on this surface were studied by cyclic voltammetry （CV） and current-timeamperomeric method. The results indicated that CdTe nanoparticles could effectivelypromote the direct electron transfer of Hb at the interface of a electrode. Theheterogeneous electron transfer rate constant, k, was calculated as 0.068 s^-1 and thetransfer coefficient,α, was 0.59. The immobilized Hb still kept its catalytic activity toH₂O₂ reduction. The apparent Michaelis-Menten constant was calculated to be 17.7μM. Itwas also found that the modified electrode could be used as a sensor for H₂O₂; the linearrange of detection was 5.0×10^-6～4.5×10^-5 M, with a detection limit of 8.4×10^-7 M. The sensor exhibited high sensitivity, reproducibility and stability.（2） Horseradish peroxidase （HRP） and lipophilic CdSe/ZnS QD were incorporatedonto the surface of GC electrodes in various ways. It was found that HRP transferselectron directly onto the GC electrode only when the electrode was modified with QDthrough evaporative deposition. The heterogeneous electron transfer rate constant k was5.80±0.70 s^-1. Absorption spectra and Fourier-transform infrared spectra showed that theconformation of HRP immobilized on the electrode has no obvious change. Further studiesindicated that immobilized HRP retains excellent catalytic activity to H₂O₂. The apparentMichaelis-Menten constant was calculated as 0.152 mM. It was also found that themodified electrode could be used as a sensor for H₂O₂, and the linear range of detectionwas 5.0×10^-6～1.0×10^-4 M, with a detection limit of 2.84×10^-7 M. The sensor exhibitedreproducibility, stability and relatively high sensitivity. The result indicated that core-shellQD could promote the direct electron transfer between protein and electrode, but theelectrochemical behavior strongly depend on modify method of QD.（3） Evaporative deposition of lipophilic CdSe/ZnS QD was characterized by variousways, the influence of deposition time and deposition temperature on the catalytic activeof HRP were studied. The results indicated that the direct electron transfer of HRP couldbe promoted preferably when QD was deposited 7 hours at 35℃. Under these conditions,the average coverages of QD and HRP on the electrode surface were 5.56×10^-8 mol/cm²and 6.47×10^-11mol/cm² respectively, and the heterogeneous electron transfer rate constantk of HRP is 6.01 s^-1.（4） Laccase was immobilized on an electrode modified with a cysteineself-assembled monolayer and coated with functionalized quantum dots. The directelectrochemistry and the catalytic kinetics of Laccase on this surface was studied by CVand current-time amperomeric method. The immobilized laccase is capable of directlytransferring an electron, the heterogeneous electron transfer rate constant, k, wascalculated as 21.7 s^-1 and the transfer coefficient,α, was 0.47. Immobilized laccaseretained its activity to oxidize ascorbic acid （AA）, and the apparent Michaelis-Mentenconstant was found to be 0.47 mM. The modified electrode was used to linearlysense AA in the 1.0×10^-5～1.4×10^-4 M concentration range, with a detection limitation of 1.4×10^-6 M.（5） Pt nanoparticle was deposited on the Pt electrode by electro-chemical deposition,the prepared PNP/Pt electrode had good electrocatalytic oxidation response to salicylicacid （SA）, and could detect SA in weak alkali condition, the response current was 9.2times that of Pt electrode, and the linear range of detection was 2.0×10^-5～5.0×10^-4 M. ThePNP/Pt electrode has low detection limit, high repeatability and stability as SA sensor, canapplicate on the detection of salicylic acid reliably.更多还原