用于细胞检测的叉指微电极阻抗传感器研究进展

叉指微电极传感器具有体积小、成本低、响应快、灵敏度高、操作方便等优点,在细胞检测方面有广泛的应用。对近几年用于细胞检测的叉指微电极阻抗传感器的研究进行了综述。重点介绍了叉指微电极的不同结构、尺寸和表面修饰等对检测精度的影响,对叉指微电极细胞阻抗传感器的不足进行了总结,并对未来的发展进行了展望。     

微电极制备、表面修饰及活体/单细胞电分析应用

微电极是指至少在一维尺度上不大于25μm的电极。微电极由于尺寸小而具有一些常规电极无法比拟的性质,如具有电流密度高、响应速度快、欧姆压降(iR降)小、信噪比高等特点。微电极特殊的性质使其在电化学测试中具有独特的优点和重要性,并在分析化学、生物学及医学等方面得到了广泛应用,尤其在生命分析领域如在单细胞检测和活体分析中具有众多重要的应用。微电极的设计制备是微电极电化学发展应用的关键,目前涌现出的制备微电极的技术有电化学刻蚀法、电沉积法、自组装技术、化学镀层技术等,这些制备方法为快速制备微电极提供了可能性。本文综述了近年来微电极的研究进展,包括微电极的特点、分类、制备方法及其单细胞检测和活体分析方面的应用,最后提出了微电极面临的挑战与发展方向。     

纳米TiN修饰平面微电极阵列在神经信息双模检测中的应用

采用氮化钛(TiN)修饰平面微电极阵列(pMEA),对其性能进行改进,开展了离体神经电生理和神经递质电化学的检测研究。采用磁控溅射法在实验室自制微电极阵列上修饰具有纳米结构的TiN材料,修饰后的微电极阻抗降低近一个数量级,背景噪声基线降至±6μV,信噪比是修饰前的1.7倍。在SD大鼠离体脑片神经电生理信号检测中,信噪比可达10∶1,能分离提取±12μV的微弱信号。神经递质多巴胺电化学信号检测下限达50 nmol/L(信噪比2∶1),浓度在0.05~100μmol/L内与电流响应的线性相关系数为0.998。实验结果表明,在微电极表面修饰纳米TiN,降低了微电极阻抗,提高了信噪比,实现了对神经信息微弱信号的检测。     

石墨烯基微电极的制备及其在电化学传感中的应用

微电极由于灵敏度高、响应快、样品用量少、操作简便等特点,近年来在化学分析、生物医学、食品安全、环境检测等领域引起人们的广泛关注。 石墨烯具有超高的比表面积、优异的电子迁移率及良好的生物相容性等优点,近年来在电化学传感领域展示出巨大的发展前景。 本文围绕石墨烯基微电极的制备及其在电化学传感中的应用展开,总结了近年来国内外同行基于石墨烯修饰微电极和石墨烯微电极在重金属离子、多巴胺、葡萄糖、H₂O₂等分子检测方面取得的研究成果。 同时探讨了石墨烯基微电极在电化学传感方面面临的挑战和发展前景。     

对神经递质多巴胺敏感的离子选择性微电极的研究

介绍了一种用于检测神经递质多巴胺的双通道离子选择性微电极。利用所合成的四对甲氧基苯硼－多巴胺活性材料,构建了对多巴胺敏感的液态膜微电极,该微电极的响应性和稳定性较好,一般无机离子和有机离子没有明显的干扰。     

微电流法直接检测非电活性气体二氧化碳

基于非电活性气体CO_2在‘二甲亚砜/铂微电极’体系中定量的电还原反应,提出微电流法常温直接检测二氧化碳.在常规气敏微电极和硅一体化薄膜微电极器件上获得了满意的气敏响应特性:好的线性响应关系、灵敏度和响应速度.用硅微机械加工技术批量构制的薄膜微电极器件,既保持了微电极的全部优点,又实现了微电流器件结构的一体化,电流响应异常稳定和重现.     

儿茶酚胺类神经递质的修饰微电极伏安法研究

本文用电化学方法在铂微盘电极的表面沉积一层铁氰化镍薄膜修饰微电极，对儿茶酚胺类神经递质具有明显的电催化作用，可有效地改善微电极伏安法检测的波形，提高分析检测的准确度和灵敏度，此法用于去甲肾上腺素针剂的样品检测，结果良好。     

微电极技术在电化学中的应用

近年来,微电极越来越多地应用于电化学研究。目前已有响应速度较快的检测微电流的电子设备,这种小尺寸的微电极在电化学测试中有独特的优点和重要性,并在医学、生物学及分析化学等方面得到了应用。     

聚甲基丙烯酸甲酯电泳芯片电化学检测氨基酸

采用集成铜微电极的聚甲基丙烯酸甲酯(PMMA)电泳芯片,实现对氨基酸的分离与检测。考察了制备的铜微电极对氨基酸的催化活性以及检测电位和分离场强对分离效果的影响。在优化条件(30mmol／L NaOH缓冲溶液中,检测电位为0．7V(vs.Ag／AgCl),进样与分离电场强度均为50V／cm)下,用3cm长的通道实现了精氨酸(Arg)与亮氨酸(Leu)的分离。     

高效细胞电融合芯片中的电场分析

细胞电融合芯片内的电场分布对细胞的控制及细胞融合效率有非常重要的意义,它是该类芯片设计的主要因素。电场分布主要由芯片内微通道和微电极的结构决定。在一个新研制的融合芯片中,采用大量微电极构成的阵列来提高融合效率。由于电极数量很多,微通道和微电极的结构和形状复杂,理论计算芯片内部电场分布具有较大难度。利用ANSYS有限元分析软件,对细胞电融合芯片中的电场分布进行模拟分析,得到其强度分布及变化梯度。通过不同设计的对比分析,提出了更加适合于细胞电融合的电极阵列结构模型——矩形梳状交叉微电极阵列,为高效细胞电融合芯片的实现奠定了基础。在矩形梳状交叉微电极阵列原型芯片的实验研究中,细胞融合(植物原生质体融合)效率约为40%,超过了传统的化学融合(小于1%)、电融合(小于10%),以及最初所采用的矩形对称梳状电极(小于20%)。表明在该融合芯片上可以实现高效的细胞电融合。     

混合溶剂中性载体镁离子选择性微电极的研究

用氯化石腊和邻硝基苯辛醚为混合溶剂制备中性载体ETH5214的镁离子选择性微电极,相对于钾离子的电位选择性系数较单独以邻硝基苯辛醚为溶剂的ETH5214镁微电极改善0.9个数量级。在纯MgCl~2和在含细胞内典型离子背景的MgCl~2溶液中,响应斜率为Nernst响应,检测下限分别为4×10^-^7mol.dm^-^3和2×10^-^5mol.dm^-^3。在pH3.5-9.5范围内,氢离子对电极的电位响应无影响。测量的重现性良好。电极的实用响应时间(t~9~5)≤3s,有效寿命长于5天。     

Building addressable libraries: The use of a mass spectrometry cleavable linker for monitoring reactions on a microelectrode array

Time-of-flight secondary ion mass spectrometry (TOF SIMS) has been used in conjunction with a mass spectrometry cleavable linker to determine the percent conversion of reactions that were conducted site-selectively on an addressable microelectrode array. When combined with fluorescence techniques for analysis of the reactions, the TOF SIMS experiment provides a means for optimization of both reaction confinement and reaction efficiency on the microelectrode arrays.     

Microelectrode Electrochemistry in Microemulsion Systems

Abstract

In this paper, we demonstrate the microelectrode electrochemistry of a simple electroactive probe (ferrocene) in SDS/n‐C₄H₉OH/H₂O microemulsion systems. The oxidation of ferrocene within the microemulsion environment was carried out at a Pt microelectrode using a three‐electrode assembly with a Pt wire acting as an auxiliary electrode and an Ag wire as the pseudo‐reference electrode. Excellent Nernstian electrochemical responses were observed. The well‐defined reversible electrochemical responses facilitated the measurement of the self‐diffusion coefficient of microemulsion droplets and introduced the possibility of probing the structural changes of microemulsion systems.     

Microdrop analysis of a bead-based immunoassay

The progress to electrochemical detection of a microbead-based immunoassay in small volumes has led to a reduced assay time and lower detection limits. Three electrochemical techniques are described for an immunoassay with detection in a microdrop. The techniques are amperometric detection with a rotating disk electrode (RDE), a microelectrode, and an interdigitated array (IDA) electrode. An enzyme-labeled sandwich immunoassay with mouse IgG as the model analyte is used to demonstrate the three techniques. The microbead assay is carried out in a test tube using a magnet to control bead collection. Once the immunocomplex is formed on the microbead, the beads are transferred to a microdrop where the enzyme, either alkaline phosphatase or β-galactosidase, generates 4-aminophenol (PAP). PAP is oxidized at the electrode with an applied potential of +290 mV vs. Ag/AgCl. For all three techniques, the upper limit of the dynamic range was 1000 ng/ml mouse IgG, and the detection limits were: 50 ng/ml for the RDE, 40 ng/ml for the microelectrode, and 26 ng/ml for the IDA electrode.     

Electrochemical determination of superoxide anions generated from a single neutrophil

The oxidation current of superoxide anions generated from a single neutrophil stimulated with Immunoglobulin G or phorbol myristate acetate has been determined with a carbon fibre microelectrode. Superoxide generation by a stimulated porcine or human neutrophil is initiated 1 min after the stimulation, reaches a maximum around 5 min later, and ends within 20 min. The current—time profiles thus determined agreed well to the time-course curves of superoxide generation obtained from conventional techniques using macroscopic numbers of cells. A sampled dc voltammogram of superoxide anions having a redox potential at around −0.3 V vs. Ag/AgCl was obtained using carbon fibre microelectrode.     

Evaluation of Poly(o‐phenylenediamine) Films for Application as Insulating Layers upon Carbon Substrates for Use within Sonochemically Fabricated Microelectrode Arrays

The formation of insulating layers of poly(o‐phenylenediamine) via electropolymerization was performed on single carbon screen‐printed electrodes. The effects of experimental parameters on the properties of the film were investigated, allowing for technique optimization. These conditions were then used to deposit films upon surfaces of 100 interconnected electrodes, with cyclic voltammetry used to study the electroactivity of the resulting electrodes. The insulating property of the film, for use in the formation of microelectrode array amperometric sensors, was evaluated. Finally, the insulated sensors were exposed to ultrasonic ablation to form microelectrode arrays, and these were subsequently assessed using optical and electrochemical techniques.     

Application of a large assembly of microelectrodes to the study of cytochrome-c and other redox proteins

A novel microelectrode assembly containing more than 1000 carbon microdisks has been used to study the interfacial electron transfer kinetics of cytochrome c and several other redox proteins. It is demonstrated that near-steady-state current–voltage curves can be obtained without solution stirring, and without significant mains interference or capacitive charging currents. In addition, it is demonstrated that concentrations of redox proteins as low as 1 μM can be detected in solution. Finally, it is shown that the surfaces of carbon microdisk assemblies can be successfully coated with thin films of poly(ester sulfonic acid), which allows reactants to be studied in a membrane-like environment.     

Chemically Modified Electrodes for Recessed Microelectrode Array

Chemical modifications on recessed microelectrode array, achieved via electrodeposition techniques are reported here. Silicon-based gold microelectrode arrays of 10 μm microband and microdisc array were selected and functionalised using sol-gel and nanoporous gold (NPG) respectively. For electrochemically assisted self-assembly (EASA) formati6154on of sol-gel, electrode surface was first pre-treated with a self-assembled partial monolayer of mercaptopropyltrimethoxysilane (MPTMS) before transferring it into the sol containing cetyltrimethyl ammonium bromide (CTAB)/tetraethoxysilane (TEOS):MPTMS (90:10) precursors. A cathodic potential is then applied. It was found that larger current densities were required in ensuring successful film deposition when moving from macro- to micro- dimensions. For NPG modification, a chemical etching process called dealloying was employed. NPG of three different thicknesses have been successfully deposited. All the modified and functionalized microelectrode arrays were characterized by both optical (SEM) and electrochemical analysis (cyclic voltammetry and impedance spectroscopy). An increase in surface area and roughness has been observed and such will benefit for future sensing application.     

粉末微电极——Ⅱ. 完全不可逆电极反应体系

在完全不可逆电极反应体系(氧和亚硫酰氯还原)中研究了粉末微电极的行为。可以用微多孔电极模型解释测得的实验结果, 粉末微电极技术可以广泛用于研究各种粉末催化剂的电催化行为并可能制备高灵敏、响应快的微型电化学传感器。