Chemical Biological Sensors Based on Advances in Conducting Electroactive Polymers

Advances in conducting electroactive polymers (CEPs) have driven the design of novel chemical and biochemical sensors. The redox properties of CEPs have been intensely studied for more than two decades with emphasis on their synthesis and characterization. Little attention has been paid to the importance of mechanism in sensor designs. However, in order to design robust and stable sensors, it is important to understand how the polymer structure, morphology, adhesion properties and microenvironment affect sensor performance. This work describes how chemical and biological sensors have been designed, fabricated, characterized and tested based on the fundamental understanding in CEPs. The use of photopolymerized conducting polymers in sensor designs is described. Four focus areas are presented in which the electronic properties of CEPs have enabled the design of novel sensors for organics, nucleic acids, biological molecules, vapors and metal ions.     

Electrochemical Synthesis and Characterization of Electroactive Conducting Polypyrrole Polymers

Conducting/electroactive polypyrrole polymers are synthesized electrochemically on glassy carbon in various electrolytes (counterions). The polymers' electroactivity is measured using cyclic voltammetry. The electrolytes are chloride, nitrate, p-toluene sulfonate, dodecyl sulfate, and dodecylbenzenesulfonate of sodium and potassium ferrocyanide. It is found that the electrolyte (dopant) markedly affects the redox behavior of the polypyrrole films.     

聚吡咯涂层的电化学合成及对神经微电极电性能的影响

通过改变掺杂剂种类、反应时间、电流密度等合成条件, 在神经微电极表面通过电化学沉积一系列厚度及形貌不同的导电高分子聚吡咯(PPy)涂层. 通过X射线光电子能谱及扫描电子显微镜对所得涂层化学组成及形貌进行表征.研究了PPy涂层对神经微电极电性能的影响. 电化学阻抗谱表明, 在神经信号相关的1 kHz频率处, 神经微电极阻抗值可降低至原来的1/55. 循环伏安曲线表明, 随PPy合成时间加长或电流密度提高, 电极总电容量随之增大.     

Amino Acid Determination Using Screen-Printed Electrochemical Sensors

The use of a screen-printed electrochemical sensor (SPES) strip, consisting of a two-electrode system (a carbon working electrode and Ag/AgCl reference electrode), for amino acid determination is reported.The behaviour of the SPES toward cysteine and tyrosine is investigated using linear sweep and hydrodynamic voltammetries. The SPES operate at a lower oxidation potential (vs. Ag/AgCl) compared with traditional carbon and platinum electrodes, in a buffer solution (pH = 7) prepared using 0.1 M phosphates and 0.1 M KCl. The linear response lies between 5 * 10⁻⁵ M and 5 * 10⁻⁴ M for both amino acids while the sensitivity is 2.95±0.03 µA mM⁻¹ for cysteine and 8.00±0.01 µA mM ⁻¹for tyrosine; the correlation coefficient is higher than 0.9980. The sensors were applied to the analysis of some commercial pharmaceutical samples, and the results suggested that the devices hold promise in this application area.     

Coupling of a Reagentless Electrochemical DNA Biosensor with Conducting Polymer Film and Nanocomposite as Matrices for the Detection of the HIV DNA Sequences

Abstract

This paper describes a reagentless electrochemical DNA biosensor applied to the detection of human immunodeficiency virus (HIV) sequences based on electrochemical impedance spectroscopy (EIS). The novel DNA biosensor has been elaborated by means of an opposite‐charged adsorption Au‐Ag nanocomposite to a conductive polymer polypyrrole (PPy) modified platinum electrode (Pt) and self‐assembly the mercapto oligonucleotide probes onto the surface of modified electrode via the nanocomposite. The duplex formation was detected by measuring the electrochemical impedance signal of nucleic acids in phosphate buffer solution (PBS). Such response is based on the concomitant conductivity changes of the PPy film and nanocomposite. The reagentless scheme has been characterised using 21‐mer synthetic oligonucleotides as models: parameters affecting the hybridization assay were explored and optimized. The detection limit is 5.0×10^?10 M of target oligonucleotides at 3σ. The potential for development of reagentless DNA hybridization analysis in the clinical diagnosis is being pursued.     

Sensitive and Selective Electrochemical Sensor Based on Molecularly Imprinted Polypyrrole Hybrid Nanocomposites for Tetrabromobisphenol A Detection

Abstract

A sensitive and selective electrochemical sensor based on electropolymerized molecularly imprinted polypyrrole and gold nanoparticles–multiwalled carbon nanotubes (AuNPs–MWCNTs) hybrid nanocomposites was developed for the determination of tetrabromobisphenol A (TBBPA). A glassy carbon electrode (GCE) was modified with MWCNTs, and the AuNPs–MWCNTs/GCE was prepared by an electrodeposition method in HAuCl₄ solution. The AuNPs–MWCNTs nanocomposite showed high electrocatalytic activity, good conductivity, and sufficient reactive sites for the direct electro-oxidation of TBBPA. The molecularly imprinted polymers (MIPs) as recognition elements were synthesized through in situ electro-polymerization of pyrrole as functional monomers in the presence of the TBBPA template molecules. Under the optimal conditions, the developed sensor exhibited good selectivity towards TBBPA compared with structural analogs, high sensitivity, and excellent producibility. The electrochemical responses of the sensor toward TBBPA were obtained in the linear range from 0.5?nM to 1?μM with a limit of detection equal to 0.24?nM at a signal-to-noise ratio of 3.     

银纳米修饰电极的制备及电化学行为

金属纳米粒子由于其小的体积和大的比表面积而具有独特的电子、光学和异相催化特性,是目前表面纳米工程及功能化纳米结构制备的一种理想研究对象[1]。银纳米粒子可广泛应用于催化剂材料、电池的电极材料、低温导热材料和导电材料等,成为近年来人们研究的热点[2,3]。在电化学方面,银纳米粒子具有比其他纳米粒子更为优异的导电性能和电催化性能。因此,研究银纳米粒子修饰电极有重要的应用价值和前景[4]。1实验部分1.1仪器CHI660电化学工作站(USA);TU-1901型双光束紫外可见分光光度计(北京普析通用仪器公司);KQ-100型超声清洗器(昆山市超声…     

以聚吡咯和纳米金为基质基于电化学交流阻抗测试的乙肝表面抗原免疫传感器研究

A novel simple immunosensing strategy for fabrication of hepatitis B surface antigen detection has been developed via electrochemical impedance spectroscopy （EIS） as a platform. At first, the conductive polymer polypyrrole （PPy） film was electrodeposited on a platinum electrode surface to adsorb the gold nanoparticles （nano-Au） via the opposite-charged adsorption technique, and then hepatitis B surface antibodies were adsorbed onto the surface of nano-Au. The modification procedure was characterized by EIS. Such spectroscopy is attributed to the concomitant conductivity changes of the polymerized pyrrole film and gold nanoparticles. The factors influencing the performance of resulting immunoelectrode were studied in detail. The linear range of the resulting immunoelectrode is from 2.6 to 153.6 ng.mL^-1 with a detection limit of 1.3 ng·mL^-1 at 3σ. In addition, the experiment results indicate that antibody immobilized on this way exhibits a good sensitivity, selectivity, high stability and a long-term maintenance of bioactivity, implying a great promising alternative approach for reagentless immunosensing analysis in the clinical diagnosis.     

Effect of the Structure of Nonuniform Conducting Polymer Films on Their Electrochemical Impedance Response

Electrochemical impedance spectroscopy is used to characterize thin p-doped polypyrrole (PPy) films in propylene carbonate (PC) solutions and poly(trifluorophenyl)thiophene (PTFPT), in solutions based on sulfolane (SF). It appears that the latter film is much less swelled compared to the former one. One consequence of this difference is that the PTFPT film shows a much higher bulk resistance compared to that for the PPy film. Another important consequence is that the swelling of the PTFPT film is essentially physically non-homogeneous. Two parallel, uncoupled paths, with different chemical diffusion coefficients, model the experimental results adequately. In order to quantify the impedance spectra for both polymer films, we use a model proposed by Rubinstein et al. explaining the difference in the diffusion coefficients of Ru(bpy)^3+/2+ ₃ within a thin Nafion film. The model can also predict the impedance spectra for composite powdery electrodes containing different particle sizes, such as composite cathodes and graphite anodes used in lithium batteries.     

电化学DNA生物传感器定量检测根癌农杆菌终止子基因片段

通过自组装法及共价法固定单链脱氧核糖核酸(ssDNA),制备了电化学DNA生物传感器。将巯基丙酸(MPA)自组装于金电极表面形成单分子膜,再利用1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐酸盐(EDC)和N-羟基琥珀酰亚胺(NHS)的活化作用将ssDNA探针序列固定于金电极表面。将ssDNA修饰的电极与待测溶液中人工合成的转基因食品中常有的根癌农杆菌终止子(NOS)基因片段进行杂交,在[Fe(CN)6]3-/4-溶液中进行循环伏安和电化学阻抗谱扫描,表征ssDNA固定及杂交过程。优化了ssDNA固定条件。待测溶液中DNA浓度在1.0×10-7～1.0×10-10mol/L范围时,其浓度的对数值和ssDNA/Au电极与dsDNA/Au电极峰电流差值的变化值呈线性相关关系,相关系数为0.9822,检出限为8.1×10-11mol/L。     

对羟基苯甲酸酯分子印迹电化学传感器的研制

利用分子印迹技术,以对羟基苯甲酸乙酯为模板分子,甲基丙烯酸为单体,在玻碳电极表面原位聚合分子印迹聚合物敏感膜.采用方波伏安法对对羟基苯甲酸乙酯在该印迹电极上的电化学行为进行了研究,当响应时间为15 min时,0.95 V(vs SCE)处的峰电流与对羟基苯甲酸乙酯的浓度在2.0×10-6 ～2.0×10-4 mol/L范围内呈线性关系,检出限(S/N=3)为1.0 μmol/L,而相同条件下,对羟基苯甲酸乙酯在控制电极上的响应非常小并对浓度变化不灵敏;同时在印迹电极上氧化峰电位较在裸电极上发生了微弱正移.同一支印迹电极对对羟基苯甲酸乙酯响应值的RSD为4.3%(n=10).该印迹电极对尼泊金酯类具有良好的选择性,对对羟基苯甲酸甲酯、丙酯以及丁酯的选择性系数分别为1.89、1.70和2.01;对结构相似的苯酚、对羟基苯甲酸、对氨基苯甲酸等响应不灵敏,对结构差异较大的如维生素C等几乎无响应.用该分子印迹电极对实际样品进行分析,加标回收率大于90%.     

Hydroxyapatite Nanoparticles Modified Graphite Electrodes for Electrochemical DNA Detection

Hydroxyapatite nanoparticles (HaNP) modified pencil graphite electrodes (PGEs) were developed for the first time in the literature, and accordingly they were applied for electrochemical monitoring of sequence‐selective DNA hybridization. The experimental conditions for HaNP modification of PGE, and DNA hybridization related to Hepatitis B Virus (HBV) DNA sequence were optimized. The microscopic and electrochemical characterization of HaNP‐PGE in contrast to the unmodified one was utilized. Under optimized experimental conditions, the selectivity of HBV DNA probe immobilized biosensor was tested against to non‐complementary (NC), mismatch (MM) sequences and the mixture of target:NC (1 : 1) or target: MM (1 : 1).     

Au/硫醇/卵磷脂双层膜的制备及其电化学表征

生命体系的许多过程发生在生物膜上,生物膜模拟体系的制备与研究一直受到人们的重视．自组装单分子膜（ＳｅｌｆＡｓｅｍｂｌｅｄＭｏｎｏｌａｙｅｒｓ,ＳＡＭｓ）特别是在金基底表面的硫醇单分子膜由于其具有良好的稳定性及有序性,因此在基础理论研究及应用技术等方...     

温度对铅阳极膜电化学性能的影响

利用线性电位扫描法、交流伏安法、电化学阻抗谱(EIS)及Mott-Schottky方程, 研究了温度对纯铅在4.5 mol/L H₂SO₄溶液中形成的阳极腐蚀膜电性能的影响. 结果表明: 温度对膜电化学性能具有显著的影响, 随着温度的升高, 膜的电阻增加, 孔隙率增加, 传递电阻减小. EIS结果表明膜的生长遵循固相机理, Mott-Schottky曲线显示腐蚀膜呈现n型半导体特性, 随着溶液温度升高, 膜内的施主密度减小.     

In Situ Synthesis and Copolymerization of Oligonucleotides on Conducting Polymers

 Two strategies of DNA biochip construction on conducting polymers are investigated. The first involves a direct electro-copolymerization of pyrrole–oligonucleotides (oligonucleotides tethered to a pyrrole group) with the pyrrole leading to a polypyrrole film bearing the oligonucleotides. Successive copolymerizations allow the transformation of a microelectrode array into a DNA array. The second methodology involves a direct in situ synthesis of oligonucleotides on a conducting polymer used as an organic electrode. In this way a 5′ electrolabile protecting group, p-nitrobenzoyl, was used. In order to construct short oligonucleotide sequences, the other protecting groups of the bases have also to be modified. Preliminary results based on this technology are shown. Received July 28, 1998. Revision October 19, 1998.     

界面可控硫醇SAMs纳米金修饰金电极的电化学行为研究

在裸金电极上自组装不同比例的4,4’-二甲基联苯硫醇(MTP)和硫辛酸(TA)混合液,形成自组装膜(MTP+TA/Au SAMs),再修饰纳米金,制得纳米金混合巯基修饰金电极(AuNPs/MTP+TA/Au)。研究了纳米金混合巯基修饰金电极的电化学行为和阻抗行为,结果表明电极表面pH值的改变对电极表面的电子转移有重要影响。对葡萄糖传感器的制备条件、测定条件、抗干扰能力等进行了讨论,结果表明修饰电极的微结构和微环境有必要进一步研究。     

Development of Pen-type Portable Electrochemical Sensor Based on Au-W Bimetallic Nanoparticles Decorated Graphene-chitosan Nanocomposite Film for the Detection of Nitrite in Water,Milk and Fruit Juices

The development and fabrication of a simple, portable, and sensitive detection tool to precisely monitor nitrite level is of growing importance in electrochemistry research, given the strong interest in the protection of drinking water quality, treatment of wastewater, food production, and control of remediation processes. This work describes the fabrication of a simple, cost-effective, pen-type electrochemical sensor based on bimetallic gold and tungsten nanoparticles electrochemically decorated on graphene-chitosan modified pencil graphite electrode (PGE) for the trace detection of nitrite in real samples. The prepared nanocomposite was characterized using XRD, SEM, and EDS. The electrochemical behavior of the sensor was evaluated by cyclic voltammetry (CV) and impedance electrochemical spectroscopy (EIS). Results revealed that the proposed sensor displayed excellent electrocatalytic activity towards electro-oxidation of nitrite with an irreversible redox reaction. The AuNPs-WNPs@Gr-Chi/PGE sensor exhibited excellent analytical performance with a wide linear range from 10 to 250 μM towards nitrite. The LOD and LOQ were calculated to be 0.12 μM and 0.44 μM, respectively. The designed electrochemical sensor was successfully applied for the detection of nitrite in water, milk, and natural fruit juice samples.     

Study of the adsorption of cytochrome c on a gold nanoparticle – modified gold electrode by using cyclic voltammetry, electrochemical impedance spectroscopy and chronopotentiometry

Adsorption of cytochrome c (Cyt c) on a gold nanoparticle – modified gold electrode was studied by using cyclic voltammetry, electrochemical impedance spectroscopy and chronopotentiometry in a phosphate buffer solution. It is shown that the charge transfer resistance is directly proportional to the amount of adsorbed Cyt c. The effects of temperature and time on the course of adsorption were also studied. The trends obtained in ΔG_ADS showed that Cyt c was found to have a smaller affinity for the modified electrode as indicated by their smaller negative ΔG_ADS values.     

基于纳米MnO2的免标记型DNA电化学生物传感器用于大肠杆菌的测定

以室温固相合成法制备纳米MnO2,通过壳聚糖（CHIT）的成膜效应将纳米MnO2固定在玻碳电极表面。DNA在MnO2/CHIT膜上的固定和杂交通过循环伏安和电化学交流阻抗进行表征。以电化学阻抗免标记法检测目标DNA,固定于电极表面的DNA探针与目标DNA杂交后使电极表面的电子传递电阻增大,以此作为检测信号可以高灵敏度地测定目标DNA。电化学阻抗谱检测大肠杆菌基因片段的线性范围为2.0×10^-11 ～2.0×10^-6mol/L,检出限为1.0×10^-12mol/L。