磁性复合纳米材料的制备及其电化学传感研究

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英文题名：Synthesis of Magnetic Nanocomposites and Their Applications in Electrochemical Sensing 作者：彭花萍 论文级别：博士 学科专业名称：微纳米材料科学与工程 中文关键词：磁性纳米复合物 ; 二茂铁 ; Fe_3O_4@SiO_2 ; Fe_3O_4@Au ; Fe_3O_4@ZrO_2 ; Fe_3O_4@Al_2O_3 ; Fe_3O_4/石墨烯 ; 金-聚多巴胺-Fe_3O_4-石墨烯 ; 蛋白质(酶)-金-聚多巴胺-Fe_3O_4 ; 葡萄糖氧化酶 ; 血红素类蛋白质 ; 磁性碳糊电极 ; 磁性玻碳电极 ; 生物传感器 ; 电催化 ; 电化学传感器 英文关键词：magnetic nanocomposite ; ferrocene ; Fe_3O_4@SiO_2 ; Fe_3O_4@Au ; Fe_3O_4@ZrO_2 ; Fe_3O_4@Al_2O_3 ; Au-polydopamine-Fe_3O_4-graphene ; Fe_3O_4/graphene ; Protein (enzyme)-Au-polydopamine-Fe_3O_4 ; glucose oxidase ; heme protein ; magnetic carbon paste electrode ; magnetic glassy carbon electrode ; biosensor ; electrocatalysis ; electrochemical sensor 学位年度：2011 导师：邱建丁 学科代码：080502 学位授予单位：南昌大学

摘要

磁性纳米材料因其易于制备、无毒且具有超顺磁性和良好的生物相容性,已被广泛应用于信息存储、磁共振成像、药物载体、癌症的诊断与治疗以及生物样品的分离与提纯等方面,也因此被认为是最有前途的材料之一。磁性复合纳米材料是磁性纳米粒子以及其他成分通过物理或化学的方法结合形成的,集成了各组分的特殊性质且具有协同效应的一类复合材料,其应用范围更加广泛。本论文设计合成了一系列性能优良的磁性复合纳米材料,例如：二茂铁功能化的Fe3O4@SiO2磁性纳米粒子、核-壳金属或金属氧化物包裹的Fe3O4磁性纳米粒子、石墨烯/Fe3O4复合纳米材料、纳米金-聚多巴胺-Fe3O4-氧化石墨烯复合纳米材料和蛋白质-金钠米粒子-聚多巴胺-Fe3O4磁性生物复合纳米粒子,并将其应用于构建性能优良的生物传感器,这一系列的研究工作充分体现了Fe3O4纳米粒子在电化学传感领域中的巨大潜在应用价值。本论文主要内容包括：
     1、对磁性纳米粒子及其复合材料的研究现状进行了综述,着重介绍了磁性纳米粒子的性质、制备方法及其功能化；详细介绍了磁性纳米粒子及其复合材料在生化医学领域中的应用；综述了电化学传感器及磁性纳米材料在电化学传感器中的应用。在以上基础上,提出了本论文的主要研究内容。
     2、制备了羧基二茂铁修饰的磁性核-壳Fe3O4@SiO2复合材料(FMC-AFSNPs),将该复合材料与葡萄糖氧化酶(GOx)及壳聚糖(CS)混合修饰于自制的磁性碳糊电极表面,构建了FMC-AFSNPs/GOx/CS复合膜生物传感器。通过循环伏安和计时电流法对传感器的电化学特性进行了研究。结果表明,固定在磁性碳糊电极表面的FMC-AFSNPs复合物良好地保持了二茂铁的氧化还原电活性,有效防止了电子介体二茂铁在电极表面的泄漏。而且,FMC-AFSNPs/CS复合膜良好的生物相容性还极大地改善了固定化GOx的生物活性,使得制备的传感器对葡萄糖具有良好的电催化氧化性能,对葡萄糖检测的线性范围为1.0±10-5～4.0×10-3M,检测限为3.2μM(S/N=3)。
     3、设计合成了一系列新型核-壳结构磁性纳米粒子(Fe3O4@Au、Fe3O4@ZrO2、Fe3O4@Al2O3等),将该功能化核-壳磁性纳米粒子通过外磁场作用固定在电极表面,进而通过蛋白质与核-壳磁性纳米粒子上的壳层之间的相互作用将血红素类蛋白质固定在核-壳磁性纳米粒子表面,从而提出了一种简单便捷的血红素类蛋白质的固定化方法。采用透射电镜、紫外光谱、交流阻抗和循环伏安等方法对核-壳磁性纳米粒子的形貌以及蛋白质的固定化过程进行了表征。结果表明,核-壳结构的磁性纳米粒子不仅有效克服了Fe3O4易团聚和易氧化等缺陷,而且具有良好生物相容性的Au、ZrO2或Al2O3等壳层能够很好地保持固定化蛋白质的生物活性。该磁性复合纳米粒子/血红素类蛋白质生物传感界面成功地实现了蛋白质和电极之间的直接电子转移及表现出对H2O2良好的电催化还原行为。该方法极大地简化了蛋白质在电极表面的固定化过程,为生物电子器件的制备开辟了新途径。
     4、在多元醇体系中,通过在石墨烯表面原位高温分解乙酰丙酮化铁(Fe(acac)3)制备了四氧化三铁/石墨烯(Fe3O4/rGO)复合纳米材料。采用透射电镜、X射线衍射、紫外-可见吸收光谱、红外光谱和电化学等方法对该复合物的形貌和性能进行了表征。利用Fe3O4具有良好的磁性性能及过氧化物酶活性,仅仅在外磁场作用下即实现了Fe3O4/rGO复合物在电极表面的固定,同时,利用Fe3O4良好的过氧化物酶活性,Fe3O4/rGO复合物修饰电极对H2O2的电化学还原展现出良好的催化性能。而且,石墨烯的大比表面积还有效提高了Fe3O4纳米粒子在rGO表面的负载量,增强了对H2O2的催化能力。Fe3O4和石墨烯的协同催化作用,使得Fe3O4/rGO复合物电极对H2O2的电催化还原能力大大增强,实现了对H2O2的高灵敏检测,测定的线性范围为2.0～983μM,检测限为0.66μM(S/N=3)。
     5、发展了一种基于纳米金-聚多巴胺-四氧化三铁-氧化石墨烯复合纳米材料(Au-PDA-Fe3O4-GO)的简单方便的生物分子固定化方法,以乙肝表面抗体(HBsAb)为例开展研究,构建了高灵敏特异性检测乙肝表面抗原(HBsAg)的电流型免疫传感器。采用透射电镜、电子能谱图和X射线衍射等方法对制备的Au-PDA-Fe3O4/GO复合纳米材料进行了表征,采用电化学方法对传感界面的构建过程进行了研究。设计合成的Au-PDA-Fe3O4/GO复合纳米材料不仅具有良好的生物相容性,能够有效保持固定化抗体的生物活性,而且,石墨烯特有的二维纳米结构还极大地增大了HBsAb在电极表面的负载量,并有效提高了复合材料的导电性。此外,利用Fe3O4自身具有的良好氧化还原电化学特性,在无需加入其它电子介体的条件下即可实现对HBsAg的电化学检测。采用示差脉冲伏安法对HBsAg测定的线性范围为0.1～180.0 ngmL-1,检出限为0.033 ng mL-1(S/N =3)。本法构建的传感界面兼具GO、PDA、Fe3O4和AuNPs的优点,对HBsAg的检测具有检出限低、灵敏度高、稳定性好等特点,具有良好的应用前景。
     6、采用一步原位化学聚合法制备了一种多功能蛋白质(酶)-金纳米粒子-聚多巴胺-四氧化三铁磁性生物纳米粒子。反应中,DA作为还原剂和聚合物单体,多种蛋白质(酶),如血红蛋白(Hb)、肌红蛋白(Mb)、辣根过氧化酶(HRP)以及葡萄糖氧化酶(GOx)为模型生物分子,HAuCl4为氧化剂,触发DA发生聚合反应,同时自身生成Au纳米粒子。采用扫描电镜、X射线能谱、紫外光谱及电化学等方法对复合物的形貌和生物分子的固定化进行了表征。结果表明,利用Fe3O4的磁性,该复合物仅在外磁场存在下就可有效固定于电极表面。而且,多巴胺原位聚合法固定蛋白质过程温和,金纳米粒子和聚多巴胺为固定化的蛋白质提供了良好的生物微环境。因此,用该方法构建的仿生纳米传感界面不仅很好地保持了固定化蛋白质的生物活性,还有效防止了固定化生物分子从电极表面的泄露。此外,金纳米粒子还可作为电子导线,有效接触蛋白质的电活性中心,并在蛋白质与电极之间建立起良好的传导桥梁,显著促进了生物分子与电极表面的直接电子传递速率。因此,该方法构建的生物传感界面不仅有效地促进了电极表面蛋白质(酶)与电极之间的直接电子转移,而且也表现出对H2O2及葡萄糖等的良好电催化行为。该方法为构建真正的第三代生物传感器件提供了有益尝试。
Magnetite nanoparticles have long been one of the most promising materials because of their good biocompatibility, strong superparamagnetic property, low toxicity and easy preparation and great potential for various biomedical applications, such as magnetic data storage, NMR imaging, targeted drug delivery, and biomolecule separation. Various magnetic nanocomposites have been intensively investigated because of their hybrid properties of the involved magnetic nanoparticles and other materials. In this dissertation, various magnetic nanocomposites with excellent properties have been designed and synthesized, such as ferrocene-modified magnetic nanoparticles, core-shell metal or metal oxide coated Fe3O4 nanoparticles, graphene/Fe3O4 composite, Au-polydopamine-Fe3O4-graphene nanocomposite, and protein-Au-polydopamine-Fe3O4 magnetic bionanoparticles and applied to construct a series of novel electrochemical sensing. The details are given as follows:
     1. Introdution
     In this section, the characteristics, synthesis methods, and modification of the magnetic nanomaterials and their composites were introduced, and their applications in biochemistry and medicine were summarized. Furthermore, we have described the electrochemical biosensor and summarized the applications of magnetic materials in electrochemistry sensing. At last, the works and innovations of this dissertation were presented.
     2. The preparation of ferrocene-modified Fe3O4@SiO2 magnetic nanoparticles and their applications for electrochemical biosensor
     A novel amperometric glucose biosensor was developed by entrapping glucose oxidase in chitosan composite doped with ferrocene monocarboxylic acid-modified magnetic core-shell Fe3O4@SiO2 nanoparticles (FMC-AFSNPs). It is shown that the obtained magnetic bio-nanoparticles attached to the surface of a carbon paste electrode with the employment of a permanent magnet showed excellent electrochemical characteristics and at the same time acted as mediator to transfer electrons between the enzyme and the electrode. Under optimal conditions, this biosensor was able to detect glucose in the linear range from 1.0×10-5～4.0×10-3 M with a detection limit of 3.2μM (S/N=3). This immobilization approach effectively improved the stability of the electron transfer mediator and is promising for construction of biosensor and bioelectronic devices.
     3. The construction of core-shell magnetic nanoparticles/heme protein nano-functional interfaces and their applications
     A simple approach for the immobilization of heme proteins using core-shell magnetic nanoparticles (Fe3O4@Au, Fe3O4@ZrO2 and Fe3O4@Al2O3) as the building block has been developed, and the direct electron transfer between the immobilized proteins and electrode was studied. The bifunctional core-shell magnetic nanoparticles were initially deposited on the electrode surface by applying a constant magnetic field, and then heme proteins were immobilized on the core-shell magnetic nanoparticles surface via interaction between the shell and the protein. Transmission electron microscope, UV-vis spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry were carried out to characterize the morphology, structure, and electrochemistry of the nanocomposite and the biofilm. The modified electrode based on this core-shell magnetic nanoparticles/heme proteins films well retained the native structure of the immobilized proteins and displayed good electrocatalytic activity to the reduction of H2O2. The proposed method simplified the immobilization methodology of proteins and showed potential application for construction of third-generation biosensors and other bio-magnetic induction devices.
     4. The synthesis of Fe3O4/graphene nanocomposite and its application in electrochemical sensing
     A novel electrochemical sensing platform based on graphene supported Fe3O4 nanoparticles (Fe3O4/rGO) composite was constructed for the detection of hydrogen peroxide (H2O2). The Fe3O4/rGO composite was prepared by one-step in situ high-temperature decomposition of the precursor iron (Ⅲ) acetylacetonate on graphene oxide sheets in polyol solution. The morphologies and characteristics of the as-prepared Fe3O4/rGO composite were investigated by using transmission electron microscopy, X-ray diffraction, UV-vis spectroscopy, Fourier transform infrared spectra and electrochemical techniques, respectively. With the advantages of the magnetism and the intrinsic peroxidase-like activity of Fe3O4 nanoparticles, the composite film could be easily fabricated in the present of external magnetic field and shows excellent electrocatalytic activity towards the reduction of H2O2. In addition, the large surface area and high electrical conductivity of graphene dramatically increased the loading capability of Fe3O4 nanoparticles and enhanced the conductivity of the composite. Together with the electrocatalytic activity of the graphene towards H2O2, the Fe3O4/rGO composite-modified electrode had a better synergistic electrocatalytic effect on the reduction of H2O2 than did Fe3O4 or graphene-modified electrode. At physiological condition, the constructed sensor showed a linear range for the detection of H2O2 from 2.0 to 983μM with a low detection limit of 0.66μM (S/N=3) and exhibited high selectivity, excellent stability and reproducibility.
     5. A label-free amperometric immunosensor based on biocompatible Au-polydopamine-Fe3O4-graphene nanocomposite
     A novel and facile biomolecule immobilization strategy based on Au-polydopamine-Fe3O4-graphene oxide (Au-PDA-Fe3O4-GO) nanocomposite was used to develop a highly sensitive amperometric immunosensor. The morphologies and characteristics of the as-prepared Au-PDA-Fe3O4-GO nanocomposite were investigated by using transmission electron microscopy, powder X-ray diffraction, energy dispersive X-ray and electrochemical techniques, respectively. The characteristics of the modified electrode at different stages of modification were studied by cyclic voltammetry and electrochemical impedance spectroscopy. In addition, the performances of the resulting immunosensor were studied by differential pulse voltammetric. The as-prepared Au-PDA-Fe3O4-GO nanocomposite not only provided a favorable microenvironment to maintain the activity of the immobilized HBsAb, but also increased the loading capacity of the HBsAb due to the two-dimensional structure of the graphene, and the present of graphene and Au nanoparticles enhanced the conductivity and charge-transport properties of the composite. In addition, due to the redox characteristic of the Fe3O4 nanoparticles, the constructed immunosensor could realize the electrochemical detection of HBsAg without using other electron mediator. The present immunosensor exhibited a wide linear range from 0.1～180.0 ng ml/-1 with a low detection limit of 0.033 ng-mL-1 at signal to noise ratio of 3. Moreover, the studied biosensor exhibited high sensitivity, good reproducibility and long-term stability. The prepared immunosensor exhibited high selectivity, low detection limit, long-term stability and good reproducibility.
     6. The synthesis of protein-polydopamine-Au-Fe3O4 nanocomposites and their application in electrochemical biosensor
     A novel protein-Au-polydopamine-Fe3O4 magnetic polymeric bionanocoparticles (protein-Au-PDA-Fe3O4 MPBNPs) with proteins entrapped at high load/activity for direct electrochemistry was designed and prepared by a one-pot in situ chemical synthesis. As representative materials here, DA as a reductant and a monomer, proteins including hemoglobin (Hb), myoglobin (Mb), horseradish peroxidase (HRP), and glucose oxidase (GOx) as the model proteins/enzyme, Fe3O4 NPs as model magnetic nanomaterial and the core of the MPBNPs, and HAuCl4 as an oxidant to trigger DA polymerization and the source of the Au nanoparticles, were simply mixed to yield protein-Au-PDA-Fe3O4 MPBNPs. Scanning electron microscope, energy dispersive X-ray, UV-vis spectroscopy, and electrochemical methods were used to characterize the protein-Au-PDA-Fe3O4 MPBNPs. Results demonstrated that the resultant protein-Au-PDA-Fe3O4 MPBNPs not only have the magnetism of Fe3O4 NPs which makes them easily manipulated by an external magnetic field, but also have the excellent biocompatibility of the functional shell which can maintain the native structure of the entrapped proteins and facilitate the direct electrochemistry of the heme proteins. Based on the direct electron transfer of the immobilized proteins, the protein-Au-PDA-FesO4 MPBNPs-modified electrode exhibited excellent catalytic performance for H2O2.

引文

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