Poly(Neutral Red)/Cholesterol Oxidase Modified Carbon Film Electrode for Cholesterol Biosensing

New amperometric cholesterol oxidase (ChOx) based enzyme biosensors for cholesterol have been developed. The enzyme was immobilised with and without glutaraldehyde cross‐linking on top of carbon film electrodes modified with redox mediators. Mediators tested were: poly(neutral red) (PNR), Prussian blue and cobalt hexacyanoferrates. Amperometric detection of cholesterol showed that PNR/ChOx modified electrodes exhibited the best characteristics; under optimised conditions cholesterol was determined at ?0.4 V vs. SCE with a detection limit of 1.9 µM. The biosensors showed good reproducibility and stability and only a small influence from potential interferents in food. Analyses of cholesterol in egg yolk were successfully performed.     

Pyruvate Oxidase Biosensors Based on Glassy Carbon Electrodes Modified with Carbon Nanotubes and Poly(Neutral Red) Synthesized in Ethaline Deep Eutectic Solvent

A novel nanostructured platform for pyruvate oxidase biosensors comprises poly(neutral red) (PNR) prepared by electropolymerization of NR in ethaline deep eutectic solvent (DES) with acid dopant, on a multiwalled carbon nanotubes (MWCNT) modified glassy carbon electrode (GCE). Characterization was by cyclic voltammetry and electrochemical impedance spectroscopy and morphology was examined by scanning electron microscopy. Ascorbate and H₂O₂ gave a better response at PNR_DES/GCE than at PNR_aq/GCE. Biosensors for pyruvate and phosphate, immobilizing pyruvate oxidase onto PNR_DES/MWCNT/GCE enabled selective determination of pyruvate and phosphate, with micromolar limits of detection. Pyruvate was determined in onion samples and phosphate in water samples.     

Application of Some Room Temperature Ionic Liquids in the Development of Biosensors at Carbon Film Electrodes

Two room temperature ionic liquids, 1‐butyl‐3‐methylimidazolium bistriflimide and 1‐butyl‐3‐methylimidazolium nitrate, were employed for enzyme immobilization in a new sol‐gel matrix and, for the first time, were successfully applied as electrolyte carriers in a biosensing system. The new sol‐gel matrix, based on 3‐aminopropyltrimethoxysilane and 1‐butyl‐3‐methylimidazolium bistriflimide mixtures, did not crack even after several weeks when kept dry, and exhibited similar analytical properties to aqueous sol‐gel based glucose biosensors. The linear range was up to 1.1 mM of glucose, sensitivity was 62 nA mM^?1 and the limit of detection was 28.8 μM. The optimum ionic liquid electrolyte carrier was found to be 1‐butyl‐3‐methylimidazolium nitrate, where the biosensor was made by electrodeposition of the redox mediator, poly(neutral red), and the enzyme was immobilized by cross‐linking with glutaraldehyde. The results showed that application of room temperature ionic liquids to biosensors is very promising and can be further exploited.     

Determination of Nitric Oxide by Glassy Carbon Electrodes Modified with Poly(Neutral Red)

Nitric oxide can be oxidized to NO⁻₂ (then to NO⁻₃) and reduced to N₂O at a glassy carbon electrode modified with the film of poly(neutral red). When the modified electrode is further coated with a thin Nafion film, the interference of NO⁻₂ can be almost thoroughly eliminated, and the electrode can be employed to detect nitric oxide.     

Highly Sensitive and Selective Glucose Biosensing at Carbon Paste Electrodes Modified with Electrogenerated Magnetite Nanoparticles and Glucose Oxidase

This work reports the advantages of carbon paste electrodes modified with electrogenerated magnetite nanoparticles. The nanoparticles present catalytic activity towards hydrogen peroxide reduction. The incorporation of glucose oxidase (GOx) and magnetite in a carbon paste matrix have made possible the development of an efficient glucose biosensor. The effect of the amount of GOx and magnetite present in the composite on the response of the biosensor was critically evaluated. The biosensors demonstrated to be highly selective, with negligible interference of ascorbic acid and uric acid. The proposed biosensor was challenged with human blood serum demonstrating an excellent correlation with the spectrophotometric method.     

聚中性红修饰玻碳电极葡萄糖生物传感器

以中性红为电子媒介体,电聚合于Nafion修饰的玻碳电极表面,以戊二醛作交联剂固定葡萄糖氧化酶,最后覆盖一层Nafion膜防止酶流失,构建一种新型葡萄糖生物传感器.详细探讨了传感器的电化学性能及对葡萄糖的最佳响应条件.结果表明,30℃时,传感器在pH 7.0的PBS中对葡萄糖的线性响应范围为1.0×10-5~5.0×10-3mol.L-1.该传感器制作简单、性能优良,有潜在应用前景.     

新型聚中性红膜修饰碳糊电极的制备、表征及应用

运用一种新型的化学引发-电聚合方式将中性红膜固定到碳糊电极表面,制备出聚中性红薄膜修饰碳糊电极(PNR/CPE)。利用循环伏安法(CV)和交流阻抗谱(EIS)对修饰电极的电化学性能进行研究,借助于扫描电子显微镜(SEM)对修饰电极表面进行表征,并采用红外吸收光谱法(IR)和紫外可见吸收光谱法(UV-Vis)对PNR薄膜结构进行测试。结果表明,中性红成功地固定在碳糊电极表面,修饰电极的表面呈现特定的立体化结构,表面的电活性位点增多,电催化性能增大。在优化条件下,将该电极应用于鲱鱼精DNA(hs DNA)的检测,PNR电极上出现了1对较强的氧化还原峰,峰电流与其浓度在1.0×10~(-6)~8.0×10~(-5)mol/L范围内呈良好的线性关系,检出限为1.0×10~(-7)mol/L。     

聚中性红膜修饰电极的电化学特性及其电催化性能

研究了中性红在玻碳电极表面电聚合成膜的方法和条件，对膜内电荷传输过程和电化学特性分别用循环伏安技术和电位阶跃暂态技术进行了初步探讨。该膜对维生素Ｃ和亚硝酸盐有较强的电催化作用，催化电流与底物浓度在很宽的范围内呈线性关系，可用于实际样品的分析。     

Direct Electrochemistry of Glucose Oxidase at Carbon Nanotube‐gold Colloid Modified Electrode with Poly(diallyldimethylammonium chloride) Coating

Glucose oxidase showed direct electrochemical transfer at glassy carbon electrodes immobilized with carbon nanotube‐gold colloid (CNT‐Au) composites with poly(diallydimethylammonium chloride) (PDDA) coatings. The modified electrode (GC/CNT/Au/PDDA‐GOD) was employed for the amperometric determination of glucose. Under optimal conditions, the biosensor displayed linear response to glucose from 0.5 to 5 mM with a sensitivity of 2.50 mA M^?1 at an applied potential of ?0.3 V (vs. Ag|AgCl reference).     

聚亚甲基蓝和纳米金修饰玻碳电极的葡萄糖生物传感器

用循环伏安法在玻碳电极上电聚合一层稳定的亚甲蓝聚合物膜,研究了这层膜在0.1mol/L磷酸缓冲溶液(pH7.0)中的电化学性质。用纳米金溶胶与聚乙烯醇缩丁醛(PVB)构成复合固酶基质,采用溶胶-凝胶法固定葡萄糖氧化酶(GOD)于亚甲蓝修饰的玻碳电极表面,制成了新型葡萄糖生物传感器。实验发现,加入纳米金后提高了酶电极对葡萄糖的电流响应,所制备的传感器具有响应快、灵敏度高、稳定性好,对葡萄糖的线性响应范围为1×10-6~3×10-3mol/L,检出限为5×10-7mol/L。并具有抗尿酸、抗坏血酸干扰的特点。     

Development of electrochemical biosensors based on sol-gel enzyme encapsulation and protective polymer membranes

Protective polymer coatings have been used to enhance the retention of enzymes in sol-gel films as immobilisation phases in electrochemical biosensors. Carbon film electrodes were electrochemically modified with poly(neutral red) (PNR). These electrodes were coated with oxysilane sol-gels incorporating glucose oxidase and an outer coating of carboxylated PVC (CPVC) or polyurethane (PU), with and without Aliquat-336 or isopropyl myristate (IPM) plasticizer, was applied. The biosensors were characterised electrochemically using cyclic voltammetry and amperometry, electrochemical impedance spectroscopy and scanning electron microscopy. Impedance spectra showed that the electrode surface is most active when the sol-gel–GOx layer is not covered with a membrane. However, membranes without plasticizer extend the lifetime of the biosensor to more than 2 months when PU is used as an outer membrane. The linear range of the biosensors was found to be 0.05–0.50 mM of glucose and the biosensor with PU outer membrane exhibited higher sensitivity (ca.117 nA mM⁻¹) in the region of linear response than that with CPVC. The biosensors were applied to glucose measurement in natural samples of commercial orange juice.     

聚中性红作电子转移介体的过氧化氢生物传感器

提出一种新的第二代电流型生物传感器。将易溶于水的电子转移介体中性红经电聚合在石墨电极表面形成一层致密、稳定的膜 ,有效的减少了其流失。并在辣根过氧化酶的表面覆盖一层明胶 ,再用戊二醛交联制备了H2 O2 传感器 ,使固定化酶保持了较高活性。该生物传感器具有较宽的线性范围 :2 .0× 10 - 5～ 2 .5×10 - 2 mol L ;检出限为 1.8× 10 - 5mol L ,达到 95 %稳态电流所用时间 <2 0s。     

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.     

Electrocatalytic Oxidation and Determination of Norepinephrine at Poly(Cresol Red) Modified Glassy Carbon Electrode

A glassy carbon electrode (GCE) was modified with electropolymerized films of cresol red in pH 5.6 phosphate buffer solution (PBS) by cyclic voltammetry (CV). The modified electrode shows an excellent electrocatalytic effect on the oxidation of norepinephrine (NE). The peak current increases linearly with the concentration of NE in the range of 3×10^?6–3×10^?5 M by the differential pulse voltammetry. The detection limit was 2×10^?7 M. The modified electrode can also separate the electrochemical responses of norepinephrine and ascorbic acid (AA). The separation between the anodic peak potentials of NE and AA was 190 mV by the cyclic voltammetry. And the responses to NE and AA at the modified electrode were relatively independent.     

Application of Square Wave Anodic Stripping Voltammetry for Determination of Traces of Ti(I) at Carbon Electrodes In Situ Modified with Bi Films

Bismuth films deposited in situ at glassy carbon and carbon film electrodes were tested for the determination of traces of Tl(I) separately and together with Zn(II) and Pb (II), in acetate buffer solution pH 3.7, using square wave anodic stripping voltammetry. Electrochemical impedance spectra in the presence of Tl(I) showed differences between the electrode substrates. The sensitivity to Tl does not depend on the presence of other ions, and was better at carbon film electrodes, although the 2 nmol L^?1 detection limit was independent of electrode substrate. Application to the measurement of Tl(I) in commercial berry juice is demonstrated.     

聚中性红修饰玻碳电极的制备及其在抗菌药物有效性检测中的应用

采用电聚合法制备了聚中性红修饰玻碳电极(PNR/GCE),运用循环伏安法(CV)对修饰电极进行表征,并以CV图中的峰电流为指标,研究了中性红浓度、扫描段数、缓冲液pH值及支持电解质NaNO_3浓度对聚合过程的影响,筛选了最佳聚合条件。继而借助中性红可作为电子媒介体的特性,以E.coli为模型微生物,通过考察E.coli活性与抗菌药物浓度的关系,构建了一种新型体外药效检测的方法,用于抗菌药物有效性的快速检测。以中性红浓度0.5 mmol/L,扫描段数Segment 30,缓冲液pH 7.0,NaNO_3浓度0.5 mol/L为最佳电极修饰条件。选择菌悬液吸光度(OD_(600)) 0.5,反应时间40 min,以标准葡萄糖-谷氨酸溶液(GGA,BOD~(220))为营养物质,此时检测抗菌药物有效性的灵敏度最高。在最佳实验条件下,头孢哌酮、阿米卡星、庆大霉素、左氧氟沙星4种抗菌药物对E.coli的半数抑菌浓度分别为34.15、27.98、8.83、11.49 mg/L;作为抗革兰氏阳性菌的万古霉素对E.coli的抑菌效果较差。上述结果与经典纸片扩散法具有良好一致性。     

聚中性红/纳米二氧化硅复合修饰电极直接测定抗坏血酸

用滴涂法和电化学聚合法制备了聚中性红/纳米二氧化硅修饰电极(PNR/nano-SiO2/GCE),并用循环伏安法和交流阻抗法研究了修饰电极表面的电化学行为。实验表明,该修饰电极对抗坏血酸(AA)表现出良好的电催化氧化性能,探讨了复合修饰电极协同增效作用的机理。用线性扫描伏安法研究了AA浓度与峰电流之间线性关系,在pH2.0的磷酸盐缓冲溶液中,AA氧化峰电流在1.8×10-6～5.0×10-3mol/L浓度范围内呈良好的线性关系,检出限为5.4×10-7mol/L(S/N=3)。该修饰电极制备简单,可用于药品及果蔬食品中抗坏血酸的直接测定。     

Enhanced Microchip Electrophoresis of Neurotransmitters on Glucose Oxidase Modified Poly(dimethylsiloxane) Microfluidic Devices

In this paper, glucose oxidase (GOx) was employed to construct a functional film on the poly(dimethylsiloxane) (PDMS) microfluidic channel surface and apply to perform electrophoresis coupled with in‐channel electrochemical detection. The film was formed by sequentially immobilizing poly(diallyldimethylammonium chloride) (PDDA) and GOx to the microfluidic channel surface via layer‐by‐layer (LBL) assembly. A group of neurotransmitters (5‐hydroxytryptamine, 5‐HT; dopamine, DA; epinephrine, EP; dobuamine, DBA) as a group of separation model was used to evaluate the effect of the functional PDMS microfluidic devices. Electroosmotic flow (EOF) in the modified PDMS microchannel was well suppressed compared with that in the native one. Experimental conditions were optimized in detail. As expected, these analytes were efficiently separated within 110 s in a 3.7 cm long separation channel and successfully detected at a single carbon fiber electrode. Good performances were attributed to the decreased EOF and the interactions of analytes with the immobilized GOx on the PDMS surface. The theoretical plate numbers were 2.19×10⁵, 1.89×10⁵, 1.76×10⁵, and 1.51×10⁵ N/m at the separation voltage of 1000 V with the detection limits of 1.6, 2.0, 2.5 and 6.8 μM (S/N=3) for DA, 5‐HT, EP and DBA, respectively. In addition, the modified PDMS channels had long‐term stability and excellent reproducibility.     

聚中性红膜修饰电极测定痕量NO2^—的研究

研究了聚中性红膜修饰电极对ＮＯ－２的催化氧化性能，建立了测定ＮＯ－２的新方法。ＮＯ－２的浓度在２．０×１０－６～５．０×１０－３ｍｏｌ／Ｌ范围内与催化氧化峰电流呈良好的线性关系，检测限为６．０×１０－７ｍｏｌ／Ｌ。若利用计时电流法分析，检测限可达８．０×１０－８ｍｏｌ／Ｌ。