脑死亡过程中谷氨酸与场电位的同步检测微电极阵列研究

高浓度胞外K+会引起神经元的去极化、谷氨酸释放、甚至细胞死亡。为研究高浓度K+对在体神经元的影响,采用微机电系统( MEMS)方法制作了一种植入式微电极阵列( MEA),其上包含形状、位置固定的电化学(50伊150μm)和电生理(直径为15μm)检测位点,可同时进行脑内神经递质谷氨酸、局部场电位信号( LFP)双模检测。将这种MEA植入到大鼠纹状体后,给大鼠皮层施加高浓度K+刺激,结果表明,高钾刺激增加了纹状体内谷氨酸浓度,同时抑制了神经电生理活动。这是首次采用双模MEA研究神经元在体死亡过程,结果验证了双模微电极阵列在体检测的可行性,可用于研究脑内神经电化学、电生理的时空关系。     

多巴胺在聚中性红修饰碳纤维微电极上的电化学行为

利用电聚合方法制备了聚中性红(PNR)修饰碳纤维微电极.根据循环伏安(CV)、电位阶跃实验结果,得出了多巴胺(DA)在PNR膜中的表观扩散系数D0=7.0×10-9cm2/s、膜表面表观标准电子转移速率常数κ=0.55 cm/s;该电极对DA响应灵敏,对抗坏血酸具有良好的抗干扰能力,可望用于活体中DA的测定.     

聚对硝基苯偶氮间苯二酚修饰电极伏安法测定多巴胺

采用循环伏安法研究了多巴胺(DA)在聚对硝基苯偶氮间苯二酚(p-nitrobenzenazo resorcinol,简称NBAR)膜修饰电极上的电化学行为,用差示脉冲伏安法对多巴胺的含量进行测定.结果表明,聚NBAR膜修饰电极对DA有明显的电催化作用.在pH4.0的磷酸盐缓冲液中,氧化峰电流与DA浓度在5.0×10-6~8.0×10-4mol/L范围内呈良好的线性关系,检测限为6.0×10-7mol/L.修饰电极可有效消除针剂中其它组分对DA测定的干扰,已用于实际样品DA含量的测定,结果令人满意.     

电还原柠嗪酸修饰电极对多巴胺和尿酸的电化学性质研究

采用循环伏安法制备了电还原柠嗪酸膜修饰碳糊电极(ECA/CPE),研究了多巴胺(DA)在该修饰电极上的电化学行为。在pH 7.0的磷酸盐缓冲溶液中,ECA/CPE对DA具有明显的电催化作用,且DA呈现出一对准可逆的氧化还原峰,其氧化峰电流与DA浓度在3.7×10-7~8.2×10-5mol/L和1.04×10-4~9.34×10-4mol/L范围内呈良好的线性关系,检出限为1×10-7mol/L(S/N=3)。使用微分脉冲伏安法,DA和尿酸(UA)在ECA/CPE上的氧化峰能完全分离,且峰电流与浓度呈良好的线性关系。该电极可用于盐酸多巴胺针剂中DA的测定以及人体尿液中UA的检测。     

蒙脱土修饰碳纤维电极的制备及其应用于活体测定脑神经递质

制备了蒙脱土修饰碳纤维电极,研究了其对神经递质多巴胺(DA)及5羟色胺(5HT)的富集作用,以及对负电性的代谢产物3,4二羟基苯乙酸(DOPAC)、5羟吲哚乙酸(5HIAA)及脑内大量存在的抗坏血酸(AA)排斥性能.该电极具有很高的灵敏度、分辨率和抗干扰性,对DA的检测下限达16×10^-8mol/L,优于传统的Nafion修饰电极,对5HT的检测下限为1×10^-7mol/L.在动物活体分析中,使用该电极成功地检测了大鼠双侧颈总动脉结扎再灌损伤时,脑纹状体中神经递质DA浓度的变化.     

高效液相-电化学检测法研究针刺对家兔血浆及脑组织中单胺类神经递质的影响

 通过高效液相 电化学检测法测定了电针刺激家兔肾旁穴前后其血浆及脑组织中单胺类神经递质去甲肾上腺素 (NE)、肾上腺素 (E)、多巴胺 (DA)和 5 羟色胺 (5 HT)含量的变化 ;研究了神经递质的变化与家兔繁殖能力的关系。该实验采用ODS柱 ,流动相为V(0 0 2mol/L柠檬酸三钠 0 0 5mol/L磷酸氢二钠 )∶V(甲醇 ) =95∶5的溶液 ,用电化学检测器检测。实验证明 ,血浆及脑组织中NE ,E ,DA和 5 HT的含量在针刺肾旁穴前后都有了显著的变化 ,说明针刺能激发家兔脑内神经元的活动 ,导致相应的递质含量的变化 ,同时使得血浆中相应含量也发生变化。     

微渗析活体取样-高效液相色谱电化学检测法测定鼠脑中的单胺类神经递质

采用微渗析活体取样技术和高效液相色谱电化学检测法,测定了鼠脑纹状体中的3种单胺类神经递质多巴胺(DA)、3,4二羟基苯乙酸(DOPAC)和5羟吲哚乙酸(5HIAA)。在3.0×10-8～1.0×10-5mol/L浓度范围内,DA、DOPAC和5HIAA的浓度分别与氧化峰的峰电流呈良好的线性关系。通过在灌流液中加入1.0×10-5mol/L的NO释放剂硝普钠(SNP),研究了NO对DA释放的影响,结果表明:受NO刺激后纹状体中DA的量为基础水平的150%。     

微芯片电泳化学发光检测多巴胺

多巴胺(Dopamine,DA)是哺乳动物的重要单胺类神经递质,多巴胺代谢异常会引起神经疾病,如癫痫、帕金森症以及老年痴呆症等~([1]).目前,测定多巴胺的方法主要有毛细管电泳法~([2]),电化学分析法~([3]),微流控芯片电泳电化学检测法~([4]).本研究采用自行构建的MCE-CL检测装置和自制的玻璃/PDMS复合芯片,建立了微流控芯片电泳-化学发光(MCE-CL)测定多巴胺的新方法,并应用于人尿样中多巴胺含量的检测.     

聚4-氨基丁酸修饰电极的制备及其对多巴胺的测定

应用电聚合的方法以4-氨基丁酸(4-ABA)为修饰剂,将4-ABA聚合在玻碳电极(GCE)表面,制得聚4-氨基丁酸修饰电极(P-4-ABA/GCE),并用于多巴胺(DA)的检测。在pH 5.0的磷酸盐缓冲液(PP)中,DA在0.488V处出现一灵敏的氧化峰,氧化峰电流与DA浓度在9.1×10-8～6.7×10-5mol/L范围内呈现线性关系。检出限为3.0×10-8mol/L。制备的修饰电极,可应用于针剂中多巴胺含量的测定。     

基于氧化石墨烯增敏的聚邻苯二胺分子印迹电化学传感器测定多巴胺

本工作结合分子印迹技术和电化学检测方法对多巴胺(DA)进行了快速测定。以DA为模板分子,邻苯二胺(o-phenylenediamine,oPD)为功能单体,在氧化石墨烯(GO)修饰电极表面通过一步电聚合法制备分子印迹电化学传感器。采用透射电镜(TEM)和扫描电镜(SEM)对GO的形貌进行了表征,通过循环伏安法(CV)和差分脉冲伏安法(DPV)对传感器的电化学性能进行了分析。当DA的浓度在0.4～2000μmol·L^-1范围内时,DA在印迹电极上的DPV峰电流值与其浓度呈线性关系,检出限为8.0×10^-8 mol·L^-1;采用该方法对实际样品中的DA进行测定,回收率在92～108%之间。     

Highly Sensitive and Selective Determination of Dopamine Based on Graphite Nanosheet‐Nafion Composite Film Modified Electrode

A graphite nanosheet (GNS)‐Nafion modified glassy carbon (GC) electrode was prepared and used for highly sensitive and selective determination of dopamine (DA). The GNS‐Nafion/GC electrode displayed excellent electrocatalytic activities towards DA and ascorbic acid (AA). The selective determination of DA was carried out successfully in the presence of AA by differential pulse voltammetry. High sensitivity (3.695 μA μM^?1) and low detection limit (0.02 μM, S/N=3) for the DA detection were obtained. These good properties can be attributed to a large amount of edge plane defects presented on GNSs and the charge‐exclusion and concentration features of Nafion.     

Voltammetric determination of dopamine in the presence of ascorbic acid at a chemically modified electrode

A Nafion/ruthenium oxide pyrochlore chemically modified electrode (CME) was used for the selective determination of dopamine (DA) in the presence of a high concentration of ascorbic acid by square-wave voltammetry. Compared to a bare glassy carbon electrode, the CME exhibits an apparent shift of the oxidation potentials in cathodic direction and a marked enhancement of the current response. The selective sensing of DA is achieved by combining the electrocatalytic function of the ruthenium oxide pyrochlore catalyst with the charge-exclusion and preconcentration features of Nation. With a preconcentration time of 60 s at a potential of −0.3 V (vs. Ag/AgCl), linear calibration plots are obtained for dopamine in 0.1 M, phosphate buffer (pH 7.4) over 0–20 μM with a detection limit (3σ) of 0.1 μM.     

Nafion-离子液体-修饰碳糊电极在抗坏血酸和尿酸存在下选择性测定多巴胺

用Nafion和亲水性离子液体溴化1-辛基-3-甲基咪唑([OMIM]Br)作修饰剂制作了Nafion-离子液体-修饰碳糊电极;在0.1 mol/L磷酸盐缓冲溶液(pH 7.40)中,用循环伏安法(CV)和方波伏安法(SWV)研究了多巴胺在该修饰电极上的电化学行为,建立了抗坏血酸和尿酸存在下选择性测定多巴胺的新方法.研究表明,该修饰电极降低了多巴胺氧化、还原反应的过电位,增大了其氧化、还原反应的峰电流,而抗坏血酸和尿酸在该修饰电极上无响应;在方波伏安曲线上,多巴胺的氧化电流与其浓度在3.0×10-8～2.0×10-6 mol/L范围内呈线性关系,检出限为1.0×10-8 mol/L.该法可用于注射液和模拟生物样品中多巴胺的测定.     

聚氨基黑10B/Nafion修饰电极上多巴胺的检测

用电化学聚合法制备了聚氨基黑10B/Nafion修饰电极,利用循环伏安法研究了多巴胺在此修饰电极上的电化学行为.在磷酸盐缓冲溶液(pH 6.0)中,多巴胺在修饰电极上呈现可逆的氧化还原峰.其峰电位都随pH值的增加而负移.多巴胺氧化还原峰电流与其浓度在0.2～30 μmol/L范围内呈良好的线性关系;检出限为1.0×10~7 mol/L.实验结果表明:本修饰电极具有良好的重现性、稳定性和较强的抗干扰能力.将此修饰电极用于多巴胺注射液和小牛血清中多巴胺的检测,结果令人满意.     

Nafion covered core–shell structured Fe3O4@graphene nanospheres modified electrode for highly selective detection of dopamine

Nafion covered core–shell structured Fe₃O₄@graphene nanospheres (GNs) modified glassy carbon electrode (GCE) was successfully prepared and used for selective detection dopamine. Firstly, the characterizations of hydro-thermal synthesized Fe₃O₄@GNs were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Then Fe₃O₄@GNs/Nafion modified electrode exhibited excellent electrocatalytic activity toward the oxidations of dopamine (DA). The interference test showed that the coexisted ascorbic acid (AA) and uric acid (UA) had no electrochemical interference toward DA. Under the optimum conditions, the broad linear relationship was obtained in the experimental concentration from 0.020 μM to 130.0 μM with the detection limit (S/N = 3) of 0.007 μM. Furthermore, the core–shell structured Fe₃O₄@GNs/Nafion/GCE was applied to the determination of DA in real samples and satisfactory results were got, which could provide a promising platform to develop excellent biosensor for detecting DA.     

Fe(CN)64−‐Doped‐Glutaraldehyde‐Cross‐Linked Poly‐L‐Lysine Film Electrode. Part 2: Stability Improvement and Selective Detection of Dopamine in the Presence of Ascorbic Acid

Highly stable Nafion‐covered hexacyanoferrate‐doped‐glutaraldehyde‐cross‐linked poly‐L ‐lysine (PLL‐GA‐Fe(CN)₆^4?/Naf) film modified glassy carbon electrode (GCE), for the selective detection of dopamine (DA) in the presence of ascorbic acid (AA), was prepared by first ion‐exchanging Fe(CN)₆^4? into PLL‐GA coating on GCE then sealing it with a Nafion outer layer. The Nafion over layer is crucial in preventing leaching of Fe(CN)₆^4? ions from the inner layer. The first layer was acting as electrocatalyst for DA oxidation and the outer coating acted as discriminating layer for selective permeation of DA in the presence of interfering anionic species. More than 90% of the initial response was retained after coating with the Nafion protecting layer compared to a huge loss (>60%) without Nafion outer layer. 5% Nafion coating was identified as optimum thickness for the selective detection of DA in the presence of AA.     

Sensitive determination of dopamine on poly(aminobenzoic acid) modified electrode and the application toward an experimental Parkinsonian animal model

Recent research on the pathology and treatment of Parkinson's disease (PD) necessitates the development of methods for analysis of dopamine (DA), an electroactive substance whose content reduces in patients with PD. The concentration variation of dopamine in an experimental Parkinsonian animal model and a treatment model was studied in this paper. For the purpose of detecting dopamine sensitively, a poly(para-aminobenzoic acid) (P-pABA) electrochemically modified glassy carbon electrode was prepared. The electrochemical behavior of the modified electrode was studied by cyclic voltammetry. Under optimum conditions, the P-pABA modified electrode showed high sensitivity to DA oxidation. Coupled with high-performance liquid chromatography, the modified electrode was utilized to detect dopamine in rat brain dialysate with the linear range over three orders of magnitude and the detection limit of 2.0x10(-8) mol l(-1) (S/N=3). By treatment with reserpinum, an experimental Parkinsonian animal model was produced. Levodopa (L-dopa) and sodium nitroprusside (SNP) were used as drugs for treatment PD in this work. The dopamine level in PD model was only 22.4% that of the control one. PD rats could recover after therapy of L-dopa or SNP and the dopamine level increased sixfold compared with those not treated with drugs.     

Electrocatalytic activities of Nafion/CdSe/Self-doped polyaniline composites to dopamine,uric acid,and ascorbic acid

Composites of Nafion, COOH-capped CdSe, and self-doped polyaniline (SPAN) were used to prepare novel chemical modified glassy carbon electrodes (Nafion/CdSe/SPAN/GCE). The electrocatalytic activities of the modified GCE to the redox reactions of dopamine (DA), uric acid (UA), and ascorbic acid (AA) were investigated by cyclic voltammetry (CV). CV curves revealed that the electrocatalytic activities of Nafion/CdSe/SPAN/GCE to oxidations of the analytes in solution of pH 7 were in the order of DA?>?UA?>?AA. This order was consistent with the strong-to-low extent of interactions between the modified GCE and the analytes. These interactions were consistent with the observations that the oxidation rate of DA followed a diffusion-controlled process whereas that of UA followed a surface adsorption-controlled process. The composites of casting at higher pH levels were found to exhibit better CdSe and SPAN dispersions in films and higher electrocatalytic activities. CdSe and SPAN exhibited insignificant synergistic effects on the oxidations of DA when cast from Nafion solutions of both low and high pHs whereas CdSe and SPAN exhibited much synergistic effects on the oxidations of UA when cast from the Nafion solution of high pH at 12.     

Spatio-temporally resolved measurement of quantal exocytosis from single cells using microelectrode array modified with poly L-lysine and poly dopamine

The subsecond, temporal, vesicular exocytosis is ubiquitous, but difficult detecting in communication mechanisms of cells. A microelectrode array(MEA), fabricated by MEMS technology, was applied successfully for real-time monitoring of quantal exocytosis from single pheochromocytoma(PC12) cell.The developed MEA was evaluated by dopamine(DA) using electrochemical methods and the results revealed that the sensitivity of DA was improved to 12659.24 μA L mmol ~(-1)cm~(-2). The modified MEA was used to detect in vitro vesicular exocytosis of DA from single PC12 cells stimulated by concentrated100 mmol L~(-1)K~+cell solution. A total of 592 spikes were measured and analyzed by three parameters and the statistical results revealed the population of each parameter was an approximate Gaussian distribution, and on average, 1.31×10~6 ±9.25×10~4 oxidizable molecules were released in each quantal exocytosis. In addition, results also indicate that a single PC12 cell probably releases the spikes with T ranging from 25.6 ms to 35.4 ms corresponding to I_(max)ranging from 45.6 pA to 65.2 pA. The devices, including a homemade computer interface and the MEA modified with polymer film, provides a new means for further research on the neural, intercellular, communication mechanism.     

Electrocatalytical Oxidation and Determination of Dopamine at Redox Polymer/Nafion Modified Electrodes

ABSTRACT

The modified glassy carbon electrodes prepared by simultaneously covering with [Os(bpy)₂(PVP)₁₀Cl]⁺ redox polymer and Nafion film exhibited excellent electrocatalytic activity for the oxidation of dopamine (DA). Dual linear regions between 1.0x10^?8-1.8x10^?5 M and 1.8x10^?5-4.0x10^?4 M with correlation coefficients of 0.998 and 0.995, respectively, were obtained for log-log plots of catalytic current versus DA concentration. The detection limit for DA determination was ca. 5 nM with 3σ. The dual-film modified electrodes eliminated efficiently the interference from AA presence in a 1000-fold concentration ratio and showed excellent reproducibility for the determination of DA. The modified electrodes have been used to determine DA concentration with both cyclic voltammetric and chronoamperometric techniques. Electrocatalytic kinetics have been studied using a rotating disk electrode. Both the addition of Nafion film and an increase in DA concentration resulted in a decrease in the electrocatalytic rate constant. An apparent Michaelis-Menten constant of 1.3 mM and maximum catalytic current of 88μA were evaluated from the chronoamperometric measurements.