【作者】 陈鹏飞；

【导师】 吴朝阳； 陈利国；

【作者基本信息】 湖南大学 ， 化学工程， 2011， 硕士

【摘要】 电化学传感器具有灵敏度高、选择性好、检测成本低、分析速度快、能在复杂环境中进行连续检测等优点,在生物工程、临床医学、环境保护、电子和食品工业具有广泛的应用价值。纳米材料具有许多优点,将纳米材料用于制备传感器,可以显著增强传感器的响应性能。磁性纳米颗粒四氧化三铁因为其独特的磁效应、电子传导性、生物相容性和催化作用,在仿生催化、材料制造、生物医学等领域受到广泛关注。生物酶具有很高的催化效率和对底物选择的高度选择性,但是酶易失活,提取困难,生产工艺不够成熟,因此开发一种具有生物仿生催化作用的材料具有重要意义。基于四氧化三铁纳米颗粒具有对过氧化氢良好的催化作用,本论文拟探索研发一系列新型纳米材料修饰的电化学传感器,并用以实现对过氧化氢的检测。近年来,电化学DAN传感器吸引了广大学者的关注,它拓展了电化学和分子生物学新的研究领域,对于临床医学和基因工程具有深远意义。本论文利用DNA特殊的生化性质制备新型电化学生物传感器,实现对多巴胺抗干扰检测,为探索生物体内电子传递和代谢提供一种新的研究手段。具体内容如下:（1）用共沉淀法合成磁性纳米颗粒四氧化三铁Fe₃O₄-NPs,并以其为传感器件,构建过氧化氢传感器。采用物理吸附法（成膜法）在玻碳电极表面修饰一层用PDDA（聚氯化二烯丙基二甲基铵）分散的Fe₃O₄-NPs（四氧化三铁纳米颗粒）敏感薄膜,成膜后再附着一层离子交换膜Nafion（全氟化磺酸酯）,用以防止敏感材料的泄露,增强电流响应。由于Fe₃O₄-NPs具有仿生催化作用,实验中所制备的电化学传感器对过氧化氢浓度在10μM～2 mM的范围内有良好的信号响应,线性相关系数0.9929。在对不同H2O2浓度分析得出的米氏方程中,线性相关系数0.9989,米氏常数为5.1 mmol/L,显示了所制备传感器对过氧化氢良好的催化性能。（2）构建碳纳米管/四氧化三铁磁性纳米颗粒层层自组装膜的电化学传感器,其中采用了化学吸附和静电吸附相结合的方法对电极进行修饰。实验中运用循环伏安法和计时电流法考察修饰电极电极的性能,如直接电化学行为、对底物的催化还原行为等,同时也探讨了碳纳米管在修饰电极中的作用。当过氧化氢浓度在5μM～2.5 mM范围时有很好的响应,而且由于化学吸附和静电吸附的作用力比普通物理吸附作用力强,因此,制备的电极具有更好的稳定性和重现性。（3）用电沉积的方法构建DNA修饰电极,该DNA修饰电极表面的负电性磷酸基团可通过静电作用吸附富集正电性的多巴胺分子,显著增强多巴胺分子的电化学氧化电流;同时该修饰电极可以有效地分离在裸电极上发生重叠的多巴胺和抗坏血酸的氧化峰,从而消除电化学氧化检测多巴胺时共存电活性组分抗坏血酸的干扰。用脉冲伏安法灵敏地、选择性地检测到了浓度低至0.05μM的多巴胺。考虑到电沉积DNA修饰电极制备的简单性和对多巴胺检测的有效性,该修饰电极可提供一个具有广泛应用前景的多巴胺分子检测平台。更多还原

【Abstract】 Due to their high sensitivity , excellent selectivity, low cost, rapid reponse and continuous detection in perplexing system, electrochemical biosensor has comprehensive valuable applications in bioengineering, clinical medicine, environmental protection, electonic and food-stuff industry. Because of a number of advantages, nanostructured materials are fitted for the preparation of sensor, and enhance their response performance. Magnetic Fe₃O₄ nanoparticles（Fe₃O₄-NPs） possess unique magnetic action, eminent electronic conduction , excellent biocompatibility and catalytic property, they have attracted considerable attentions in many fields, including material production, mimetic catalysis, biomedicine, and so on. Nature enzymes own high catalytic efficiency and perfect selectivity for substrate, however, they are relatively difficult to be extracted and critical to the environmental condition. Furthermore, the enzymes cannot keep a long-term stability due to their inherent instability, so the assembly-line production of nature enzymes may suffer from lots of difficulties. Thereore , it may make sense for exploiting functional materials. In this study, we succeeded to fabricate an electrochemical sensor based on novel nanomaterials, and used for the detection of hydrogen peroxide. Electrochemical DNA biosensor integrates electrochemistry with molecular biology, which makes far-reaching influence for clinical medicine and genetic engineering, as a result, a great number of attentions are awared by scholars recently. According to the above discusses, an original electrochemical DNA sensor was prepared to detect dopamine without interference. At the same time, the sensor paves a new way to the study of electrone transfer and metabolism in life. The details are described as follows:（1） Fe₃O₄-NPs were synthesized by co-precipitation method. After preparation , the self-synthesized nanoparticles were empolyed as a part of sensor and used for constructing modified electrode. We adopted physical adsorption method to manufacture electrode. The procedures are illuminated in the following essay. First of all, Fe₃O₄-NPs were dispersed in PDDA solution, then we added several drops to the carbon electrode. After the liquid drops dried in the air, another kind of drop called Nafion was added onto the carbon electrode , successively, which could prevent from the sensitive materials letting out. Fe₃O₄-NPs possess mimetic catalysis to hydrogen peroxide. In this experiment, the electrochemical sensor represented great response behavior to hydrogen peroxide with a linear rangeof 10μM～2 mM, and the related coefficient was 0.9929. According to Michealis equation based on the analysis of different concentration of hydrogen peroxidase, the related coefficient was 0.9989 and the Michaelis constant was 5.1 mmol/L,respectively,indicting that the self-preparation sensor displayed excellent catalysis capabililties to hydrogen peroxidase.（2） We fabricated CNTs and Fe₃O₄-NPs mixed electrode by chemical and static adsorption method. The functionalized electrode capabilities were investigated by cyclic voltammograms（CVs） and amperometric i-t curve, such as direct CVs, electrocatalytic CVs and advantages of the carbon nanotubes. The sensor could be used for the detection of hydrogen peroxide, and the linear range was 5μM～2.5 mM . Because the force between chemical and static adsorption were greater than simple physical adsorption, so this modified electrode represented properties in stability and repeatbalility.（3） DNA modified electrode was constructed by electrodeposition. The carbon electrode surface was overlayed by DNA after electrodeposition. In the rear of DNA, there exited much phosphate anion with negative charge, which could arrest dopamine, for dopamine moleculars were positive. This process could evidently amplify the anodic current. More importantly, the modified electrode successfully separated the anodic peaks between dopamine and asorbic acid , compared to normal bare electrode. We used impulse voltammograms to detect dopamine selectively and sensitively. The concentration of dopamine was allowed to 0.05μM could be detected, and the low limit is 0.05μM. Considering the preparation of electrodeposition DNA modified electrode was convient and efficient detection for dopamine, it may provide a broad platform for the detection of dopamine.更多还原