An improved ELISA for the determination of tobacco mosaic virus with linear sweep voltammetry detection based on a new system of PAP-H2O2-HRP

An improved ELISA for the determination of tobacco mosaic virus (TMV) with linear sweep voltammetry based on a new system of p-aminophenol (PAP)- H₂O₂- horseradish peroxidase (HRP) has been developed. The enzymatic product 3-[(4-hydroxyphenyl)amino]-4-(2-amino-5-hydroxyphenyl)-6-[(4-hydroxyphenyl)imino]-2,4-cyclohexadiene-1-one, produced from HRP catalyzing the oxidation of PAP with H₂O₂, yields a sensitive linear sweep voltammetric response at a potential of –0.45 V (vs. SCE) in Britton-Robinson (BR) buffer solution. By using this voltammetric peak, HRP can be measured with a detection limit of 0.4 mU/L and a linear range of 1.0 ～ 1.0 × 10² mU/ L. The detection limit for the clarified TMV is 4.0 ng/mL and the highest dilution ratio detected for the infected leaf sap is 1?:?3.9 × 10⁶. The processes of the enzyme-catalyzed reaction and the electro-reduction of the product of the enzyme-catalyzed reaction have been investigated.     

An improved ELISA for the determination of southern bean mosaic virus with linear sweep voltammetry detection based on new system of PAP-H_2O_2-HRP

An improved enzyme-linked immunosorbent assay (ELISA) for the determination of southern bean mosaic virus (SBMV) with linear sweep voltammetry based on a new system of p-aminophenol (PAP)-H2O2-horseradish peroxidase (HRP) has firstly been developed. The enzymatic product 3-[(4-hydrox-yphenyl) amino]-4-(2-amino-5-hydroxyphenyl)-6-[ (4-hydrox-yphenyl)imino]-2,4-cyclohexadiene-l-one, produced from the oxidation of PAP with H2O2 catalyzed by HRP, yielded a sensitive linear sweep voltammetric response at - 0.45 V ( vs. SCE) in Britton-Robinson (BR) buffer solution. Based on the voltammetric peak, HRP can be measured with a detection limit of 0.4 mU/L and a linear range of 1.0-1.0 × 102 mU/ L. The detection limit for the SBMV is 8.0 ng/mL and the highest dilution ratio for the detection of infected leaf sap is 1: 1.5×105.     

Detection of TMV with ODA-H(2)O(2)-HRP voltammetric enzyme-linked immunoassay system

o-Dianisidine (ODA)-H₂O₂-horseradish peroxidase (HRP) voltammetric enzyme-linked immunoassay system has firstly been used for the detection of tobacco mosaic virus (TMV). HRP catalyzes strongly the oxidation reaction of ODA by H₂O₂, the product of which produces a sensitive second order derivative linear sweep voltammetric peak at potential of −0.56 V (versus SCE) in Britton–Robinson (BR) buffer. HRP activity has been measured with this voltammetric peak and TMV detected through immunoreaction. The detection limit for HRP is 9.25×10^-7 mU l⁻¹ and the linear range is 2.5×10⁻⁶–5.0×10⁻⁴ mU l⁻¹. The detection limit for the clarified TMV is 0.25 ng ml⁻¹ and the highest dilution ratio detected for the infected leaf sap is 1:8×10⁵. The sensitivity for TMV detection with this method is higher than that with the enzyme-linked immunosorbent spectrophotometric assay (ELISA) using ODA-H₂O₂-HRP system. The processes of the enzyme-catalyzed reaction and the electro-reduction of the product of the enzyme-catalyzed reaction have been described.     

Detection of ferritin in human serum with a MAP-H(2)O(2)-HRP voltammetric enzyme-linked immunoassay system

A voltammetric enzyme-linked immunoassay based on new system of m-aminophenol (MAP)-H(2)O(2)-horseradish peroxidase (HRP) has firstly been developed and used for the detection of HRP, labelled HRP and ferritin in human serum. HRP or labelled HRP catalyzes the oxidation reaction of MAP with H(2)O(2), the product of which produces a sensitive voltammetric peak at potential of -0.46 V (vs. SCE) in Britton-Robinson (BR) buffer solution. By using this voltammetric peak, HRP can be measured with a detection limit of 9.5x10(-1) mU/l and a linear range of 2.5-2.5x10(2) mU/l. The detection limit to ferritin is 0.25 ng/ml and the linear range 0.25-320 ng/ml. The processes of the electro-reduction of the product of the enzyme-catalyzed reaction have been investigated in detail.     

PAP-H2O2-HRP酶促反应产物光谱及电化学研究

前文［１］首次提出了以对氨基酚（ＰＡＰ）为底物的ＰＡＰ－Ｈ２Ｏ２－辣根过氧化物酶（ＨＲＰ）伏安酶联免疫分析新体系,并成功地应用于烟草花叶等植物病毒的血清学检测．在此之前,我们也曾报道过一些伏安酶联免疫分析新体系［２,３］．迄今,还没有人对 ＨＲＰ催化 Ｈ２Ｏ２氧化 ＰＡＰ的酶促反应进行过探讨．Ｐｒａｔｉ等［４］报道了在铜催化作用下,Ｏ２氧化对氨基酚生成３－［（４－个羟苯基）氨基」－４－（２－氨基－５－羟苯基）－６－［（４－羟苯基）亚胺基］－２,４－环己二烯基－１－酮．本文的实验结果与此文献不符． 为…     

MAP-H~2O~2-HPR伏安酶联免疫分析新体系和光谱及电化学研究

提出了间氨基酸(MAP)-H~2O~2-辣根过氧化物酶(HRP)伏安酶联免疫分析新体系.本方法以线性扫描二阶导数伏安法检测HRP催化H~2O~2氧化MAP的产物,用于游离HRP和各种HRP标记物的测定,灵敏度均高于经典的ELISA显色光度法.测定游离HRP的线性范围为1.0x10^-^8-1.0x10-6/L,检测限达3.8x10^-^9g/L.制备出了HRP催化H~2O~2氧化MAP的产物纯品并应用电化学分析,高效液相色谱,元素分析,紫外-可见光谱,红外光谱,^1H核磁共振谱,^1^3C核磁共振谱及质谱等技术对体系酶促反应进行了深入的研究.在选择的酶促反应条件下,生成的产物为2-氨基-5-[(3-差苯基)]-2,5-环己烯基-1,4-二酮.提出了酶催化反应机理及其产物的电极还原过程。     

Comparison of Electrochemical and Spectro-Photometric Detection in Hrp-Based Elisa for Tobacco Mosaic Virus

ABSTRACT

An electrochemical method was compared with a spectrophotometric method using a horseradish peroxidase (HRP)-based indirect enzyme-linked immunosorbent assay (ELISA) with direct antigen coating (DAC) technique for the determination of tobacco mosaic virus (TMV). In substrates for a spectrophotometric HRP-based ELISA method, was selected as the substrate for the electrochemical method as well as the spectrophotometric method. 2, 3-Diaminophenazine is the product of the oxidation of OPD with H₂O₂ catalyzed by HRP in the selected conditions. It is electroactive and has a sensitive voltammetric response at -0.93 V (vs. Ag/AgCl) in alkaline solution. The detection limit of free HRP, by second-order derivative linear-sweep voltammetry, is 1.1 mU/L. This method can be further used to detect TMV antigen. The peak current is linear with TMV concentration in the range of 0.25-5.0 ng/mL. The detection limit for TMV is 0.25 ng/mL and the highest dilution ratio detected for the infected leaf sap is 1:102400. Compared with the classical OPD ELISA spectrophotometric method, the detection limits of the electrochemical method for the clarified TMV and the infected leaf sap detection are about ten and four times lower, respectively.     

Enzyme-catalyzed reaction of voltammetric enzyme-linked immunoassay system based on OAP as substrate

The o-aminophenol (OAP)-H_2O_2-horseradish peroxidase (HRP) voltammetric enzyme-linked immunoassay new system has extremely high sensitivity. HRP can be measured with a detection limit of 6.0×10~-(10) g/L and a linear range of 1.0×10~(-9)—4.0×10~(-6) g/L. The pure product of H_2O_2 oxidizing OAP catalyzed by HRP was prepared with chemical method. The enzyme-catalyzed reaction has been investigated with electroanalytical chemistry, UV/Vis spectrum, IR spectrum, ~(13)C NMR, ~1H NMR, mass spectrum, elemental analysis, etc. Under the selected enzyme-catalyzed reaction conditions, the oxidation product of OAP with H_2_O2 catalyzed by HRP is 2-aminophe-noxazine-3-one. The processes of the enzyme-catalyzed reaction and the electroreduction of the product of the enzymecatalyzed reaction have been described.     

联苯胺-H_2O_2-HRP伏安酶联免疫分析体系测定植物病毒TMV和TRSV

提出了联苯胺－Ｈ２Ｏ２－辣根过氧化物酶（ＨＲＰ）伏安酶联免疫分析体系测定植物病毒烟草花叶病毒（ＴＭＶ）和烟草环斑病毒（ＴＲＳＶ）的新方法。ＨＲＰ标记的羊抗兔酶标记抗体ＩｇＧ－ＨＲＰ可以催化Ｈ２Ｏ２氧化联苯胺的反应,其氧化产物在Ｂｒｉｔｏｎ－Ｒｏｂｉｎｓｏｎ（ＢＲ）缓冲溶液中在－０．６２Ｖ（ＳＣＥ）左右产生灵敏的线性扫描二阶导数伏安峰,可以测定ＩｇＧ－ＨＲＰ。根据ＩｇＧ－ＨＲＰ与植物病毒及其抗血清的免疫反应,可以间接测定植物病毒。本法测定ＴＭＶ的检出限为０．２５ｎｇ／ｍＬ,线性范围为０．２５～５０００ｎｇ／ｍＬ;测定ＴＲＳＶ的检出限为１．５ｎｇ／ｍＬ,线性范围为１．５～３０００ｎｇ／ｍＬ;测定ＴＭＶ烟草病叶澄清液的最高稀释比为１∶１００００。检测灵敏度高于酶联免疫吸附显色光度法（ＥＬＩＳＡ）     

Enzyme-catalyzed reaction of OPD-H202-HRP voltammetric enzyme-linked immunoassay system

Enzyme-catalyzed reaction of o-phenylenediamine (OPD)-H_z0₂-horseradish peroxidase (HRP) voltammetric enzyme-linked immunoassay system has been studied in detail with electrochemical analysis, high performance liquid chromatography (HPLC), ultraviolet/visible (UV/Vis) spectroscopy, infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The pure product of H₂0₂ oxidizing OPD catalyzed by HRP was prepared with chemical method. The experimental results of voltammetry and HPLC indicate that only one product of enzyme-catalyzed reaction has been obtained under the selected enzyme-catalyzed reaction conditions. Identifications by UV/ Vis spectrum, IR spectrum and¹³C NMR spectrum show that the product is 2,3-diaminophenazine. The processes of the enzyme-catalyzed reaction and the electroreduction of the product of the enzyme-catalyzed reaction are described. Project supported by the National Natural Science Foundation of China     

Electrochemical studies of 1,5-dihydroxynaphthalene as substrate for voltammetric enzyme immunoassay

Immunoassay is one of the biochemical analytical techniques using the specific antigen antibody com-plexation for analytical purposes. It has extensive ap-plication in clinical diagnostics, prevention and cure of diseases, and virus diagnostics. The presentation and progress of immunoassay methodology are one of the greatest achievements of bioanalytical chemistry. It is estimated that several-hundred millions of immuno-analytical determinations are carried out every year all over the world. E…     

PAP-H2O2-HRP伏安酶联免疫分析新体系测定人血清总甲状腺素

目前临床检测中测定总甲状腺素(T₄)的常用方法有间接血凝试验、琼脂双扩散及ELISA等方法^[1].其中ELISA法是目前较为流行的检测方法,但灵敏度不高.伏安酶联免疫分析法具有广阔的应用前景^[2,3].     

Reagentless amperometric biosensor highly sensitive to hydrogen peroxide based on the incorporation of Meldola Blue, fumed-silica and horseradish peroxidase into carbon paste

 A reagentless amperometric sensor highly sensitive to H₂O₂ has been prepared by incorporating fumed silica, horseradish peroxidase (HRP) and Meldola Blue into carbon paste. The efficient mediating ability to shift electrons between HRP and the carbon paste electrode via Meldola Blue was investigated by cyclic voltammetric and amperometric measurements. Reproducibility, response time, detection limit, selectivity and effects of applied potential, temperature and pH on the response of the sensor are reported. The high sensitivity of the sensor with a detection limit of 0.1 μmol/l arose from the high efficiency of the bioelectrocatalytic reduction of hydrogen peroxide via HRP and Meldola Blue. The dependence of the Michaelis-Menten constant on the applied potential and the mediator concentration has been investigated and the results are presented. Received: 20 December 1995/Revised: 13 March 1996/Accepted: 16 March 1996     

An Ni(chitin)2 modified nitric oxide microsensor

The development of a simple, sensitive, selective, and stable amperometric nitric oxide microsensor is described. It is based on Ni(chitin)₂ mediators immobilized on a platinum, Nafion modified electrode. The detection of NO is based on the Ni(chitin)₂ catalysis of NO oxidation at an anodic potential of +0.74 V (vs. SCE). The catalytic peak current is linear for a NO concentration in the range of 8.5 × 10^–8 mol/L to 1.5 × 10^–5 mol/L, with a correlation coefficient of 0.9992. The detection limit of the microsensor is 5.0 × 10^–8 mol/L. It is suitable for the direct measurement of NO in biological systems. Received: 5 February 1999 / Revised: 15 June 1999 / Accepted: 17 June 1999     

A new cloud-point preconcentration approach for the spectrophotometric determination of p-aminophenol in the presence of paracetamol with 2-(2-Hydroxyphenyl)-1H-benzimidazole as a coupling reagent

A preconcentration and determination method for trace p-aminophenol (PAP) in paracetamol was developed. Cloud-point extraction (CPE) was employed for the preconcentration of p-aminophenol prior to spectrophotometric determination using Triton X-100 (TX-100) as an extractant. The determination is based on the reaction of p-aminophenol with 2-(2-hydroxyphenyl)-1H-benzimidazole (HPBI) at room temperature in the presence of an oxidant to produce indophenol blue dye. The dye formed is subsequently entrapped in micelles of the surfactant TX-100. The surfactant-rich phase shows maximum absorbance at 650 nm and the proposed method is linear in the 0.1 to 5.0 mg mL⁻¹ concentration range. By preconcentrating 10 mL of the sample solution, a detection limit as low as 55 ng/mL was obtained after a single-step extraction and the experimental concentration factor achieved for this method was found to be 10. The stoichiometric composition of the dye is 1: 1 (PAP: HPBI). Some parameters such as HPBI, KIO₄, Na₂CO₃, and TX-100 concentration, extraction temperature, incubation, and centrifugation time, and the sample volume were investigated in detail. The established procedure was successfully adopted for the determination of p-aminophenol in the presence of paracetamol in various pharmaceutical preparations. The text was submitted by the authors in English.     

Enzyme biosensor based on the immobilization of HRP on SiO<Subscript>2</Subscript>/BSA/Au composite nanoparticles

In this work, an enzyme biosensor based on the immobilization of horseradish peroxidase (HRP) on SiO₂/BSA/Au/thionine/nafion-modified gold electrode was fabricated successfully. Firstly, nafion was dropped on the surface of the gold electrode to form a nafion film followed by chemisorption of thionine (Thi) as an electron mediator via the ion-exchange interaction between the Thi and nafion. Subsequently, the SiO₂/BSA/Au composite nanoparticles were assembled onto Thi film through the covalent bounding with the amino groups of Thi. Finally, HRP was immobilized on the SiO₂/BSA/Au composite nanoparticles due to the covalent conjugation to construct an enzyme biosensor. The surface topographies of the SiO₂/BSA/Au composite nanoparticles were investigated by using scanning electronic microscopy. The stepwise self-assemble procedure of the biosensor was further characterized by means of cyclic voltammetry and chronoamperometry. The enzyme biosensor showed high sensitivity, good stability and selectivity, a wide linear response to hydrogen peroxide (H₂O₂) in the range of 8.0 × 10^-6 ∼ 3.72 × 10^-3 mol/L, with a detection limit of 2.0 × 10^-6 mol/L. The Michaelies-Menten constant K_M^app K_M^{app} value was estimated to be 2.3 mM.     

Determination of metformin based on amplification of its voltammetric response by a combination of molecular wire and carbon nanotubes

Molecular wires containing copper(II) (CuMW), in the form of the coordination polymer (Cu(II)₄(bpp)₄(maa)₈(H₂O)₂).2H₂O (bpp=1,3-bis(4-pyridyl)propane, maa=2-methylacrylic acid), and multiwalled carbon nanotubes (CNT) have been combined to prepare a paste electrode (CuMW/CNT/PE). The voltammetric response of the CuMW/CNT/PE to metformin (MET) was significantly greater than that of electrodes prepared from other materials, because of both the surface effect of CuMW and CNT and coordination of MET with the Cu(II) ion in the CuMW. A novel voltammetric method for determination of MET is proposed. In pH 7.2 Britton–Robinson buffer, using single sweep voltammetry, the second-order derivative peak current for oxidation of MET at 0.97 V (relative to SCE) increased linearly with MET concentration in the range 9.0 × 10⁻⁷–5.0 × 10⁻⁵ mol L⁻¹ and the detection limit was 6.5 × 10⁻⁷ mol L⁻¹. Figure When a combination of molecular wires containing copper(II) (CuMW) and multiwalled carbon nanotubes (CNT) was used to prepare a paste electrode (CuMW/CNT/PE) the voltammetric response to metformin (curve c) was significantly higher than that at a carbon/PE (curve a) or a CNT/PE (curve b), because of the amplification effect of CNT and CuMW. A novel voltammetric method is proposed for determination of MET     

Solvothermal Synthesis, Crystal Structure, and Properties of the New Oxothiomolybdate Ni(dien)2[Mo2O2S6]

Summary.  The reaction of NiCl₂ · 6H₂O, Na₂MoO₄ ċ 2H₂O, and sulfur in a mixture of diethylenetriamine and 0.2 M ammonia solution (1:4) under solvothermal conditions leads to the formation of orange-red crystals of the oxothiomolybdate Ni(dien)₂[Mo₂O₂S₆] (dien = diethylenetriamine) in nearly 100% yield. The structure consists of [Ni(dien)₂]²⁺ cations and discrete dimeric [Mo₂O₂S₆]²⁻ anions. The compound crystallizes in the monoclinic space group P2₁/c (a = 8.726(2), b = 18.111(4), c = 14.419(3) ?, β = 101.686(3)°). Upon heating the compound decomposes in a single step starting at about 250°C. The final decomposition product was identified by X-ray powder diffractometry as MoS₂ and Ni₃S₂. Spectroscopic data as well as detailed synthetic procedures for Ni(dien)₂[Mo₂O₂S₆] are reported. Received November 6, 2000. Accepted November 17, 2000     

Growth of Anodic Films on Compound Semiconductor Electrodes: InP in Aqueous (NH4)2S

 Film formation on compound semiconductors under anodic conditions is discussed. The surface properties of InP electrodes were examined following anodization in an (NH₄)₂S electrolyte. The observation of a current peak in the cyclic voltammetric curve was attributed to selective etching of the substrate and a film formation process. AFM images of samples anodized in the sulfide solution revealed surface pitting. Thicker films formed at higher potentials exhibited extensive cracking as observed by optical and electron microscopy, and this was explicitly demonstrated to occur ex situ rather than during the electrochemical treatment. The composition of the thick film was identified as In₂S₃ by EDX and XPS. The measured film thickness varies linearly with the charge passed, and comparison between experimental thickness measurements and theoretical estimates for the thickness indicate a porosity of over 70%. Cracking is attributed to shrinkage during drying of the highly porous film and does not necessarily imply stress in the wet film as grown. During the growth of the thick porous film, spontaneous current oscillations have been observed. The frequency of oscillation was found to be proportional to the current density, regardless of whether the measurements were carried out during a potential sweep or at constant potential. Thus, the charge passed per oscillation remained constant. A characteristic value of approximately 0.3 C · cm⁻² was measured under potential sweep conditions, and a similar value was obtained at constant potential.     

Growth of Anodic Films on Compound Semiconductor Electrodes: InP in Aqueous (NH4)2S

Summary.  Film formation on compound semiconductors under anodic conditions is discussed. The surface properties of InP electrodes were examined following anodization in an (NH₄)₂S electrolyte. The observation of a current peak in the cyclic voltammetric curve was attributed to selective etching of the substrate and a film formation process. AFM images of samples anodized in the sulfide solution revealed surface pitting. Thicker films formed at higher potentials exhibited extensive cracking as observed by optical and electron microscopy, and this was explicitly demonstrated to occur ex situ rather than during the electrochemical treatment. The composition of the thick film was identified as In₂S₃ by EDX and XPS. The measured film thickness varies linearly with the charge passed, and comparison between experimental thickness measurements and theoretical estimates for the thickness indicate a porosity of over 70%. Cracking is attributed to shrinkage during drying of the highly porous film and does not necessarily imply stress in the wet film as grown. During the growth of the thick porous film, spontaneous current oscillations have been observed. The frequency of oscillation was found to be proportional to the current density, regardless of whether the measurements were carried out during a potential sweep or at constant potential. Thus, the charge passed per oscillation remained constant. A characteristic value of approximately 0.3 C · cm⁻² was measured under potential sweep conditions, and a similar value was obtained at constant potential. Received October 16, 2001. Accepted (revised) December 21, 2001