高载酶量酶/酶免疫电极的制备及其电化学机理研究

本文利用扫描电镜和电化学方法确定了最佳镀铂电位,并进一步研究了酶电极和酶免疫电极在基体电极镀铂和未镀铂条件下的米氏常数、电化学反应速率常数和反应速度控制步骤。比较分析了生物电极的最佳实验条件。     

聚邻苯二胺膜电极中辣根过氧化物酶的电子传递

利用酸的电化学固定法制备含辣根过氧化物酶的聚邻苯二胺膜电极，研究其伏安行为及对Ｈ２Ｏ２还原的生物电催化作用，结果表明，在所述生物电催化反应中酶与聚合物基质 直接电子传递，但对新制的酶电极而言，电聚合时生成并包埋在酶膜中的寡聚体可作为电子传递体加速氧化态酶的再生，根据酶电极电流响应实验曲线的拟合，发现经态酶的再生速度随是极电位的变化表观上符合Ｔａｆｅｌ关系式，提出了酶反应学参数的测定方法。     

有机磷农药酶生物传感器研究进展

酶生物传感器（EBS）以简单、廉价、易于微型化等优势成了有机磷农药（OPs）传统分析方法的最佳替代品。本文从识别OPs的酶及识别机理、电化学EBS、酶的固定化技术、高分子材料的酶固定载体不同角度综述了有机磷农药酶生物传感器研究近况,并重点介绍了一次性丝网印刷酶电极。     

辣根过氧化物酶的电化学固定化及其对H2O2的生物电催化…

利用电化学固定化方法制备了聚吡咯／辣根过氧化物酶（ＰＰ／ＨＲＰ）膜电极，并研究了其电化学行为，在除氧的磷酸盐缓冲液介质中，ＰＰ／ＨＲＰ电极加速Ｈ２Ｏ２的还原，归因子酶加成物的直接电子传递，探索ＨＲＰ与电子传递体Ｋ４Ｆｅ（ＣＮ）６在聚吡咯（ＰＰ）膜中的同时固定化条件及其膜电极的电化学行为，实验证实，Ｋ４Ｆｅ（ＣＮ）６在酶膜中的存在使得Ｈ２Ｏ２的还原电位强烈正移，在－０．０５Ｖ的工作电位下能对Ｈ２Ｏ２     

辣根过氧化物酶／聚邻苯二胺膜电极的制备与性能研究

辣根过氧化物酶（ＨＲＰ）／聚邻苯二胺（ＰＰＤ）膜电极由ｐＨ７．０磷酸盐缓冲溶液介质中邻苯二胺在玻碳电极上的电聚合而制得。讨论了ＨＲＰ电化学固定化的过程。所得酶电极呈现生物催化活性,可在没有电子传递体存在的情况下催化Ｈ＿Ｏ＿２还原。该反应发生在聚邻苯二胺氧化还原的电位区,聚合物参与了酶的电子转移过程。分析了旋转ＨＲＰ／ＰＰＤ电极上酶反应的动力学,讨论了动力学常数的影响因素。     

用自制酶电极测定牛奶中残留青霉素

用自制酶电极测定牛奶中残留青霉素;生物电化学传感器;青霉素残留     

聚吡咯葡萄糖氧化酶电极的生物电化学响应

采用分步骤合过程，制备了以聚吡咯膜为载体的葡萄糖氧化酶电极，探讨了其生物电化学响应特性，计算了酶催化反应的有关动力学参数。与溶解态酶相比，该电极表现出良好的生物电化学特征，而且酶蛋白对溶液温度的稳定性有显著提高。     

钴卟啉修饰碳纤维束葡萄糖酶微电极的研究

生物电化学传感器的微型化研究是目前生物传感器研究中的一个很活跃的方向。我们曾用钴卟啉修饰碳纤维柱电极,并以它为基底制成了葡萄糖微传感器。为加强电极的抗折断能力,本文把约1千支碳纤维(φ9μm)做成碳纤维束盘微电极,在其表面修饰四苯基钴卟啉后,以其为基底制成了葡萄糖酶电极。将其用于流动注射分析,可以大大提高线性响应上限。     

1,4-二氧六环介质中辣根过氧化物酶电极的性能研究

用交联法制备辣根过氧化物酶(HRP)电极, 在1,4-二氧六环介质中研究其电化学行为。实验表明, 固定化的HRP在有机相中仍保持活性并可与电极进行直接电子传递, 因而能在没有其它电子传递体存在的条件下催化H~2O~2的电化学还原反应。当亚铁氰化物与酶共修饰至电极上之后, 它起着电子传递体的作用, 使HRP电极的性能大为改善。根据不同条件下得到的动力学参数, 讨论了影响酶电极性能的因素。     

酶电极电子转移途径的研究进展

酶的活性中心与电极表面的电子转移直接影响酶电极的性能和特征。自1962年第一个酶电极报道以来,科学家们不断探索新的方式实现酶与电极间电子转移并取得了较大的进展,使生物传感器由第一代依靠氧与葡萄糖氧化酶中的活性中心反应测量氧的消耗为原理,发展到第三代实现酶的活性中心与电极表面之间的直接电子转移,即所谓的"无试剂电化学生物传感器"。然而,探究酶电极内在电子转移机理以及设计能够满足不同应用要求并适合大规模量产、价格合适的酶电极仍然是研究的热点。本文综述了主要的电子转移方式以及相应的优缺点,以及笔者团队开发的使用氧化还原聚合物实现电子转移的方法,并对其应用前景进行展望。     

Electrochemical Peroxidase‐Catalase Clark‐Type Biosensor: Computed and Experimental Response

A bioelectrode containing immobilized catalase and peroxidase was built using a Clark‐type oxygen electrode. The bioelectrode responded to hydrogen peroxide (H₂O₂) as well as to acetaminophen (Ac). The sensitivity of the bioelectrode for H₂O₂ was 0.35 mM O₂/mM H₂O₂ and for Ac it was 0.23–1.05 µM O₂/µM Ac at pH 6.6 and 25 °C. The limit of detection of Ac varied from 12 to 44 µM. The half‐time of the bioelectrode response to hydrogen peroxide was 36 s. The modeling of the bioelectrode action was performed digitally at transition and steady‐state conditions using finite difference technique. The calculated half‐time of the bioelectrode response to hydrogen peroxide was 53 % larger and the steady‐state response 11 % less than experimentally determined. The response to Ac was 2–3 times smaller in comparison to the experimental values. The calculated response change correlated with the experimentally determined when the catalase and peroxidase concentrations in the biocatalytical membrane changed 3–4 orders of magnitude. The simulations of the bioelectrode response revealed that the bioelectrode acts in diffusion limiting conditions at almost all enzymes concentrations. The model appears to be promising for optimization of the bioelectrode response.     

Ionic Liquid‐Hemoglobin‐Carbon Paste Composite Bioelectrode and Its Electrocatalytic Activity

A new carbon ionic liquid paste bioelectrode was fabricated by mixing hemoglobin (Hb) with graphite powder, ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIMBF₄) and liquid paraffin homogeneously. Nafion film was cast on the electrode surface to improve the stability of bioelectrode. Direct electrochemistry of Hb in the bioelectrode was carefully investigated. Cyclic voltammetric results indicated that a pair of well‐defined and quasi‐reversible electrochemical responses appeared in pH 7.0 phosphate buffer solution (PBS), indicating that direct electron transfer of Hb was realized in the modified electrode. The formal potential (E^0′) was calculated as ?0.316 V (vs. SCE), which was the typical characteristic of the electrochemical reaction of heme Fe(III)/Fe(II) redox couple. Based on the cyclic voltammetric results the electrochemical parameters of the electrode reaction were calculated. This bioelectrode showed high electrocatalytic activity towards the reduction of trichloroacetic acid (TCA) with good stability and reproducibility.     

Glucose Dehydrogenase Based Bioelectrode Utilizing a Synergistic Scheme of Substrate Conversion

A Bioelectrode utilizing a synergistic scheme of substrate conversion was built using glucose dehydrogenase from Acinetobacter calcoaceticus immobilized on the surface of a graphite electrode. At saturated glucose concentration the bioelectrode responded to the low reactive substrate hexacyanoferrate(III) with a sensitivity of 0.0035 µA/µM cm². The response of the bioelectrode increased up to the 3.4×10⁴ fold in the presence of high reactive organic electron acceptors (mediators). The increase of the response depended on the concentration of the mediators and their chemical nature. The sensitivity of the bioelectrode to mediators reached 7.3–77 µA/µM cm². The comparison of the bioelectrode sensitivity with kinetic parameters of enzyme action in homogeneous solution revealed good correlation between the sensitivity of the bioelectrode and the predicted value from the kinetic scheme of the reactivity of mediators. This confirms a synergistic scheme of bioelectrode action.     

An optimised glucose oxidase bioelectrode exhibiting high performance direct electron transfer

A glucose oxidase (GOd) bioelectrode exhibiting high performance, direct electron transfer (DET) has been prepared. Unprecedented redox peak current densities of 1 mA cm(-2) were observed alongside a clear electrochemical response to glucose. This system shows potential as a low cost, high performance enzymatic bioelectrode.     

Microstructural and Potential Dependence Studies of Urease-Immobilized Gold Nanoparticles–Polypyrrole Composite Film for Urea Detection

Gold nanoparticle–polypyrrole nanocomposite film was electrochemically deposited in a single-step polymerization of pyrrole in the presence of 3-mercaptopropionic acid (MPA)-capped gold nanoparticles (GNPs) and p-toluenesulfonic acid (pTSA) on the surface of an indium tin oxide (ITO)-coated glass plate. The carboxyl functional groups surrounding the GNPs within the polymer matrix were utilized for the immobilization of urease enzyme through carbodiimide coupling reaction for the construction of a Urs/GNP(MPA)–PPy/ITO-glass bioelectrode for urea detection in Tris–HCl buffer. The resulting bioelectrode film was characterized by atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), contact angle measurement, Fourier transform infrared spectroscopy (FTIR), and electrochemical techniques. The potentiometric response of the bioelectrode made of polymer nanocomposite films of two different thicknesses prepared at 100 and 250 mC cm^?2 charge densities, respectively, was studied towards the urea concentration in Tris–HCl buffer (pH 7.4). The thin polymer nanocomposite film-based bioelectrode prepared at 100 mC cm^?2 charge density exhibited a comparatively good potentiometric response than a thick 250 mC cm^?2 charge density film with a linear range of urea detection from 0.01 to 10 mM with a sensitivity of 29.7 mV per decade.     

Glassy carbon paste electrodes modified with polyphenol oxidase: Analytical applications

The electrochemical behavior of a glassy carbon paste electrode (GCPE) is evaluated in comparison to that of graphite paste electrode (gPE) and glassy carbon electrode (GCE). Important shifting in the peak potentials and increases in the peak currents for catechol, ascorbic acid, dopamine and hydroquinone were obtained for the GCPE and its usefulness for the development of phenol and catechol biosensors was also evaluated. Both, pure mushroom polyphenol oxidase (PPO) and fresh mushroom tissues were used as biorecognition elements. The effect of the binder percentage in the composite material was also studied. The bioelectrode was used for the determination of dopamine and acetaminophen in pharmaceutical formulations and for the detection of polyphenols in wine and tea. The bioelectrode demonstrated to be very stable as the response remained around 90% after four months at 4 °C.     

Langmuir-Blodgett film based on MEH-PPV for cholesterol biosensor

Cholesterol oxidase (ChOx) has been immobilized onto conducting poly[2-methoxy,5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)/stearic acid (SA) Langmuir-Blodgett film transferred onto octadecanethiol (ODT) modified gold plate. The ChOx/MEH-PPV/SA LB film bioelectrode exhibits has been characterized by FT-IR, contact angle, and atomic force microscopy. The response of the ChOx/MEH-PPV/SA LB film bioelectrode carried out using differential pulse voltammetry (DPV) studies reveal linearity from 1.29 to 12.91 mM of cholesterol concentration and response time as 30 s. This ChOx/MEH-PPV/SA bioelectrode exhibits values of correlation coefficient as 0.9939, standard deviation as 0.0029 μA and limit of detection as 1.66 mM. UV-visible spectrophotometer studies reveal that 5.2 × 10⁻³ U of ChOx are actively working per cm² area of ChOx/MEH-PPV/SA LB film bioelectrode and this bioelectrode is thermally stable upto 55 °C with reusability of about 60 times.     

A novel enzymatic bioelectrode system combining a redox hydrogel with a carbon NanoWeb

A novel bioelectrode system has been prepared in which an enzyme and a conducting polymer hydrogel are combined in a nanostructured scaffold. The latter consists of fibres of carbon NanoWeb, grown by chemical vapour deposition onto reticulated vitreous carbon (RVC). The catalytic currents produced by this new bioelectrode system are significantly larger than those obtained using conventional electrodes.     

Electrophoretically deposited polyaniline nanotubes based film for cholesterol detection

Polyaniline nanotube (PANI-NT) based films have been fabricated onto indium-tin-oxide (ITO) coated glass plates via electrophoretic technique. These PANI-NT/ITO electrodes have been utilized for covalent immobilization of cholesterol oxidase (ChOx) using glutaraldehyde (Glu) as cross-linker. Structural, morphological and electrochemical characterization of PANI-NT/ITO electrode and ChOx/Glu/PANI-NT/ITO bioelectrode have been done using FT-IR spectroscopy, SEM, electrochemical impedance spectroscopy and cyclic voltammetry techniques. Response studies of the ChOx/Glu/PANI-NT/ITO bioelectrode have been carried out using both linear sweep voltammetry and UV-Visible spectrophotometry. The results of the biosensing studies reveal that this bioelectrode can be used to detect cholesterol in wide detection range of 25-500 mg/dL with high sensitivity of 3.36 mA mg(-1) dL and fast response time of 30 s at pH 7.4. This bioelectrode exhibits very low value of Michaelis-Menten constant of 1.18 mM indicating enhanced interactions between cholesterol and ChOx immobilized onto this nanostructured PANI matrix.     

Glutathione-s-transferase based electrochemical biosensor for the detection of captan

The proposed electrochemical biosensor based on the inhibition of glutathione-s-transferase (GST) onto SAM modified gold due to captan was developed and determined by CV technique. The bioelectrode exhibited improved fast response time (12 s) with the detection limits 0.25–16 ppm, percentage inhibition >72% and high sensitivity 4.5 uA/ppm at standard optimal conditions. The recovery experiment results were found between 77% and 144% from spiked water sources. The bioelectrode was regenerated by DTT and reusable. The bioelectrodes were characterized by UV–visible, CV, AFM and STM. Thus, the proposed electrochemical biosensor is not only detected captan but also its metabolite and promising for real-time analysis of small molecules of environmental interest.