Analyte peptidomimetics selected from phage display peptide libraries: a systematic strategy for the development of environmental immunoassays

Due to their simplicity, speed, low cost, and specificity, immunoassays have become a useful tool for the analysis of environmental pollutants. Once the anti-hapten antibodies are produced, the same hapten or a related molecule is conjugated to a tracer enzyme or coating protein to set up the assay. Here we report the use of peptides that mimic the analyte as advantageous substitutes of competing haptens. These peptides, which open opportunities for innovation in the development of tracer reagents, can be selected from phage display libraries in a straightforward systematic manner. The concept was proven using assays for the herbicides molinate and atrazine as model systems. Several characteristics of the selection process that may affect the final assay were analyzed, such as the phage coat proteins fused to the peptide, the use of linear or constrained peptide libraries, the effect of the concentration of analyte used during the selection process, and the use of monoclonal or polyclonal antibodies as selector molecules. In all cases we found that the selected peptides performed with improved sensitivity as compared with the chemical hapten conventional assays, showing an analogous cross-reactivity pattern. Interestingly, the phage particles perform as robust and highly standardized assay reagents, and due to their filamentous repetitive structure, they function as sensitive multienzymatic reporters.     

Development of a McAb-based immunoassay for parathion and influence of the competitor structure

A specific monoclonal antibody (McAb) for parathion was produced. Based on this McAb, a battery of competitors as coating antigens were used to develop homologous and heterologous indirect competitive enzyme-linked immunosorbent assays (ELISAs) for parathion. The relationship between the heterology degree of the competitor and the sensitivity of the corresponding immunoassay was investigated. Results showed that, when the specific McAb was used in the ELISA experiment, competitors should have a certain degree of homology with the immunizing hapten for immunoassays, and the best performance occurred when the competitor hapten was highest heterologous to the target analyte. With the most suitable competitor, a sensitive and selective ELISA was developed. The IC₅₀ value of the ELISA was 2.94 ng/ml with a detection limit (IC₂₀) of 0.70 ng/ml. The average recoveries of parathion in spiked water, soil, cucumber and rice were 88.09%, 93.15%, 91.37% and 83.42%, respectively.     

Open sandwich immunoassay: a novel immunoassay approach based on the interchain interaction of an antibody variable region

Despite their general applicability, conventional sandwich immunoassays suffer from the requirements of two antibodies recognizing different epitopes, and multiple long incubation/washing steps. In addition, the assay is not applicable to the measurement of low-molecular-weight haptens due to their size. Recently, a novel sandwich-type immunoassay that can overcome the limitations of conventional sandwich immunoassays was proposed. The assay, which utilizes antigen-dependent stabilization of an antibody variable region, requires less time and handling, and is particularly suitable for hapten measurement. The principle could be applied to several homogeneous assay formats, and the method has been shown to have superior sensitivity, as well as a lower time requirement compared to conventional assays.     

Analysis of nonylphenol: advances and improvements in the immunochemical determination using antibodies raised against the technical mixture and hydrophilic immunoreagents

The development of an enzyme-linked immunosorbent assay (ELISA) for the detection of technical nonylphenol (NP) is reported. The preparation of specific antibodies has been addressed using an immunizing hapten with a four-carbon atom spacer arm placed at the ortho position that preserves both the hydroxyl group and the complexity of the branched nonyl chain mixture of the technical NP. The synthesis of the immunizing hapten 5-(2-hydroxy-5-nonylphenyl)-pentanoic acid has been accomplished through a four-step synthetic pathway using the NP commercial technical mixture as the starting material. Three types of competitor haptens have also been prepared depending on the location of the spacer arm: in ortho position to the phenol group (type A), attached to the oxygen atom (type B), and in para position, substituting the nonyl chain (type C). Drawbacks produced by the hydrophobicity of the NP or of the hapten derivatives have been circumvented by using a highly hydrophilic carrier molecule such as a high-molecular-weight aminodextran as a coating support for antigen in an indirect ELISA format. A reproducible and sensitive indirect competitive ELISA has been finally obtained, reaching a limit of detection of 2.3 +/- 0.9 microg L(-1) and an IC50 value of 29 +/- 5 microg L(-1) (both N = 16). A coefficient of variation of 11% for assays performed on different days (N = 5; IC50 = 30 +/- 3 microg L(-1)) demonstrates the assay reproducibility. The assay also recognizes the nonylphenol polyethoxylates to a different degree depending on the length of the ethoxylate chain. Recovery values in the range between 96 and 100% have been obtained using spiked blind aqueous samples although the sample preparation procedure used has been shown to have a great influence on the method accuracy. A preliminary evaluation of the analytical protocol established has been performed using real water samples.     

糖皮质激素广谱特异性单克隆抗体的制备及其ic-ELISA方法的建立

将氢化可的松半抗原HYD通过活化脂法与钥孔戚血蓝蛋白（keyhole limpet hemocyanin,KLH）偶联获得氢化可的松完整抗原KLH-HYD,并对小鼠肌肉注射此抗原,使小鼠免疫;通过杂交瘤技术获得1 株能够稳定分泌氢化可的松的单克隆抗体细胞株HYD-C1,并通过腹水制备大量抗体。将氢化可的松半抗原HYD和地塞米松半抗原DEX通过活化脂法分别与卵清蛋白（ovalbumin,OVA）偶联作为包被原,建立糖皮质激素的间接竞争酶联免疫吸附检测（indirect competitive-enzyme linked immunosorbent assay,ic-ELISA）方法。结果：在同源包被情况下氢化可的松灵敏度为1.63 ng/mL,异源包被情况下灵敏度为0.24 ng/mL;在交叉抑制实验中,异源策略中的各糖皮质激素灵敏度均高于同源策略中的结果,异源策略条件下很好地覆盖了本研究中所检测的糖皮质激素,使该抗体具备良好的广谱特异性。在异源策略添加回收实验中平均添加回收率在77.5%～111.3%之间,落在合理范围内,满足检测需求。结论：成功制备出氢化可的松单克隆抗体,建立了同源和异源策略糖皮质激素检测方法,结果发现异源策略中糖皮质激素的灵敏度高于同源策略,并使该方法具有更好的广谱特异性。     

An immunoassay to evaluate human/environmental exposure to the antimicrobial triclocarban

A sensitive, competitive indirect enzyme-linked immunosorbent assay (ELISA) for the detection of the antimicrobial triclocarban (TCC) was developed. The haptens were synthesized by derivatizing the para position of a phenyl moiety of TCC. The rabbit antisera were screened and the combination of antiserum 1648 and a heterologous competitive hapten containing a piperidine was further characterized. The IC(50) and detection range for TCC in buffer were 0.70 and 0.13-3.60 ng/mL, respectively. The assay was selective for TCC, providing only low cross-reactivity to TCC-related compounds and its major metabolites except for the closely related antimicrobial 3-trifluoromethyl-4,4'-dichlorocarbanilide. A liquid-liquid extraction for sample preparation of human body fluids resulted in an assay that measured low part per billion levels of TCC in small volumes of the samples. The limits of quantification of TCC were 5 ng/mL in blood/serum and 10 ng/mL in urine, respectively. TCC in human urine was largely the N- or N'-glucuronide. TCC concentrations of biosolids measured by the ELISA were similar to those determined by LC-MS/MS. This immunoassay can be used as a rapid, inexpensive, and convenient tool to aid researchers monitoring human/environmental exposure to TCC to better understand the health effects.     

Development of a sensitivity‐improved immunoassay for the determination of carbaryl in food samples

BACKGROUND: With the aim of developing a highly sensitive immunoassay for carbaryl, a hapten which had high similarity to carbaryl was synthesised using a safer and more practical approach. After it was conjugated to horseradish peroxidase, direct competitive heterologous enzyme‐linked immunosorbent assay (CD‐ELISA) was optimised and characterised. The assay performance conditions were investigated in details. Enhanced chemiluminescence ELISA (ECL‐ELISA) was also used in preliminary studies. RESULTS: The assay obtained an IC₅₀ value (the concentration causing 50% inhibition) of 2 µg kg^?1, which was 12‐fold more sensitive than previous results of homologous CD‐ELISA. In ECL‐ELISA, the IC₅₀ was further decreased 10‐fold to 0.2 µg kg^?1. The CD‐ELISA developed was applicable for broad conditions, and could be applied on various food samples with a more convenient pre‐treatment. Average recoveries were in a range of 88.3–101.7%. The results correlated well with those obtained using high‐performance liquid chromatography (HPLC) analysis (R² = 0.989). CONCLUSION: The ELISA developed was a great improvement in the determination of carbaryl, showing that the immunoassay developed was a simple, rapid and efficient method that was reliable for the detection of carbaryl and suitable for rapid quantitative or qualitative determination in food samples. Copyright © 2010 Society of Chemical Industry     

Development of a class-specific ELISA for sulfonylurea herbicides (sulfuron screen)

The development of a direct competitive ELISA for the detection of a broad range of sulfonylurea herbicides (SUs) is described. Polyclonal antibodies were generated in rabbits using three different immunizing haptens. Antiserum with the broadest specificity was obtained with a mesosulfuronbenzylamine derivative which was coupled via a succinic acid spacer to keyhole limpet hemocyanine. A heterologous enzyme tracer which did not contain the succinic acid bridge was prepared using activated horseradish peroxidase. The direct competitive ELISA was optimized and applied for spiked tap and surface water samples. From 30 SUs, 8 compounds showed a molar cross-reactivity (CR) higher than 100% (this value was set for the hapten) and 11 compounds CRs between 10% and 100%. The ELISA can detect 16 SUs at a concentration of 0.1 microg/L or lower. Different surface and tap water samples were spiked with chlorimuron ethyl, metsulfuron methyl, or primisulfuron methyl at concentrations of 100, 200, or 500 ng/L and subsequently analyzed by both ELISA and HPLC-UV. Correlation analysis revealed good agreement between both methods (r2 = 0.983/0.948/0.982; n = 21 for each analyte). Using ELISA, no sample pretreatment other than filtration was necessary.     

基于异源包被的 曲安奈德竞争酶联免疫检测方法

为监控曲安奈德的滥用情况,本研究建立了曲安奈德竞争酶联免疫检测方法。将曲安奈德(Triamcinolone acetonide,TCA)半抗原通过活泼酯法与钥孔戚血蓝蛋白(keyhole limpet hemocyanin,KLH)偶联获得曲安奈德完整抗原TCA-KLH;通过免疫小鼠、细胞融合及筛选获得一株能够稳定分泌抗曲安奈德的单克隆抗体细胞株,制备并纯化了腹水抗体。将TCA和地塞米松(Dexamethasone,DEX)半抗原通过活泼酯法分别与牛血清白蛋白(bovine serum albumin,BSA)偶联作为包被原,建立曲安奈德同源及异源的间接竞争酶联免疫分析方法(indirect competitive enzyme linked immunosorbent assay,ic-ELISA)。在同源包被情况下,曲安奈德灵敏度为5.4 ng/mL,而DEX异源包下灵敏度为0.53 ng/mL。未观察该方法到对哈西奈德、布地奈德、安西奈德以外的其他糖皮质激素的交叉反应。在添加回收实验中,使用20%甲醇水溶液提取动物组织的添加回收率在75%~95%之间。该方法能有效应用于动物组织中曲安奈德的快速筛查。     

Impact of acid on survival of Vibrio vulnificus and Vibrio vulnificus phage

Three strains of Vibrio vulnificus and V. vulnificus phages were tested for acid sensitivity at 21 degrees C. V. vulnificus strain 304 was more resistant to pH 4.0 than strains CVD-1 and A-9, whereas acid sensitivities of V. vulnificus strains at pH 3.0 and 2.0 were similar. V. vulnificus phage strain 110A-7 was more resistant to pH 4.0 than strain 153A-7, whereas acid sensitivities of phage strains at pH 3.5 and 3.0 were similar. Numbers of V. vulnificus and its phage were close to the limit of detection after 100 s at pH 2.0 and after 24 min at pH 3.0. Acid D-values at 21 degrees C decreased as pH decreased for both V. vulnificus and phages. D-values of phage strains at pH 3.5 were 10-fold greater than those of host strain at pH 4.0. D-values of phage strains were slightly greater than those of host strain at pH 3.0. These results suggest that V. vulnificus and its phage were very sensitive to pH of less than 3.0, although V. vulnificus phages were more resistant to acid than their host.     

半抗原免疫分析在食品安全检测中的应用

综述近几年来关于小分子半抗原的设计、人工抗原合成的研究,以及人工抗原合成中尚存在的问题和计算机模拟技术在半抗原合成中的应用;介绍多克隆抗体、单克隆抗体、卵黄抗体及基因工程抗体在食品安全检测中的应用,分析近年来ELISA、胶体金免疫层析和新兴的免疫传感器技术研究与应用现状和发展趋势。半抗原免疫学检测方法具有较低的检测极限、快速、方便、低廉等优势,是食品安全检测的发展方向。半抗原合成的可控设计、有效抗体的规模化生产,通过与新型免疫分析技术结合以期达到高通量、低成本、实时多重检测是今后食品安全免疫学检测中重要的技术突破点。     

Development of an Enzyme-Linked Immunosorbent Assay for the Detection of Difenoconazole Residues in Fruits and Vegetables

An indirect, competitive enzyme-linked immunosorbent assay (ic-ELISA) for the detection of difenoconazole was developed. Two haptens were designed and successfully synthesized. Hapten 1 had a particular moiety of difenoconazole, while hapten 2 had its full structure. The polyclonal antibodies against hapten-protein conjugates were prepared by immunizing rabbits. After optimization of the conditions, the detection limit (IC₁₅) and sensitivity (IC₅₀) were 4.58 and 29.10 μg L^?1, respectively. The cross-reactivities of the antibody with 11 triazole fungicides were all less than 0.1%, which showed that the antibody had excellent specificity. The recoveries of difenoconazole from the spiked samples ranged from 89.70 to 102.31% with good accuracy. The matrix effect was easily removed using a simple, rapid, and efficient extraction method on fruits and vegetables. The detection limit was all 229 μg kg^?1 in fruits and vegetables. To validate the ic-ELISA, samples were spiked with difenoconazole at three different concentrations and simultaneously analyzed using high-performance liquid chromatography (HPLC). The results showed a good correlation between the ic-ELISA and HPLC data (R ² = 0.9970). As a result, the developed immunosorbent assay is suitable for the quantitative determination of difenoconazole in fruits and vegetables.     

拟除虫菊酯及其代谢物免疫检测的研究进展

作者主要介绍了检测拟除虫菊酯类农药及其代谢物的酶联免疫法和荧光免疫法。通过应用新型纳米材料(如磁纳米粒子,镧系发光纳米材料)以及噬菌体展示技术提高免疫检测的灵敏度,并对拟除虫菊酯类农药及其代谢物免疫检测的发展方向进行了展望。     

Comparison of Chicken IgY and Mammalian IgG in Three Immunoassays for Detection of Sulfamethazine in Milk

Antibodies are the most important reagents for the development of highly sensitive and specific immunoassays to quantify analytes of interest in food and environmental samples. While immunoglobulin G (IgG)-derived antibodies from rabbit and mouse are traditionally employed in immunoassays, recent findings suggest that chicken egg yolk antibody (immunoglobulin Y (IgY)) provides several advantages over mammalian IgG. However, limited studies to date have examined the possibility of replacing IgG with IgY in immunoassays. In the current investigation, the performance of chicken IgY and IgG derived from rabbit and mouse was systematically compared in terms of sensitivity, specificity, and matrix effect under parallel conditions with three typical assay formats, specifically, indirect competitive enzyme-linked immunosorbent assay (icELISA), fluorescence polarization immunoassay (FPIA), and colloidal gold immunochromatographic assay (GICA), for detection of sulfamethazine (SMZ) as the reference molecule. We evaluated and discussed the influence of different coating antigens, tracers, and physicochemical factors on the performance of IgY and IgG in the immunoassays. Under optimized conditions, the sensitivities of icELISA (IC₅₀ values of 6.70, 4.76, and 1.66 ng mL^?1 with recoveries of 86.1–131.8% and precision of <?12%) and FPIA (IC₅₀ values of 24.79, 20.87, and 10.83 ng mL^?1 with recoveries of 81.8–120.2% and precision of <?17.3%) based on both IgY and IgG were sufficient to detect SMZ in milk while only GICA based on mouse IgG provided acceptable sensitivity. Our collective data indicate that IgY could be an acceptable alternative to mammalian antibodies in some situations (in icELISA and FPIA) for use in the development of effective immunoassays for screening and detection of veterinary drug residues in food samples.     

三氯杀螨醇胶体金免疫快速检测试纸条研制及在茶叶中的应用

目的 建立一种基于胶体金免疫层析法的三氯杀螨醇快速检测试纸条的研制方法,并阐述其在新鲜茶叶中的应用。方法 以三氯杀螨醇为原料,用琥珀酸酐对其衍生化合成半抗原;用活化酯法将半抗原与白蛋白偶联得到人工抗原;用人工抗原免疫小鼠获得单克隆抗体。用上述原料制备出本研究试纸条。结果 所研制试纸条对茶叶中三氯杀螨醇检测限为0.2mg/kg,检测时间8min;可特异性地检测三氯杀螨醇的残留量,而对其他与三氯杀螨醇结构或功能相似的农药无交叉反应;准确性高;稳定性好;操作简便;检测成本低。结论 本研究提供的试纸条适宜基层实验室的大批量样本检测和田间现场快速检测,能够实现从源头上控制污染茶叶的流通上市。     

Atypical antibody specificity: advancing the development of a generic assay for sulphonamides using heterologous ELISA

Development of immunoassays with broad specificity recognition of the sulphonamide drugs has proved surprisingly difficult in previous work. We have taken an antiserum specific for sulphachlorpyridazine in an ELISA system homologous for immunogen and solid phase conjugate and used it in a heterologous ELISA format. The assay proved to have broad specificity, recognising 15 out of 21 drugs tested. Despite low cross‐reactivity (<1%) for seven of the drugs tested, a fully optimised assay could prove useful as a multiresidue method for the group of drugs. The results provide evidence regarding the binding characteristics of the antibody and the immunogenicity of the target. © 2002 Society of Chemical Industry     

呋喃西林代谢物多克隆抗体制备及酶联免疫吸附分析方法

为了建立检测呋喃西林代谢物(SEM)的酶联免疫吸附分析方法(ELISA),将所设计合成的系列半抗原与牛血清白蛋白(BSA)偶联制备免疫原并免疫新西兰大白兔,筛选获得源于新颖半抗原H3的具有高亲和力、高特异性抗SEM多克隆抗体。同时,基于设计合成的系列同/异源包被抗原,考察了不同结构包被原对ELISA灵敏度的影响,发现H4-OVA作为异源包被原建立SEM的ELISA检测方法可获得最佳的检测效果,结果显示:ELISA方法的半抑制浓度(IC50)为12.37ng/mL;定量检测线性范围(IC20～IC80)为0.439～110.78ng/mL;检测限(IC10)达0.07ng/mL,达到了国内外相关检测限量要求,可应用于实际食品样品检测。     

Identification of a Biomarker for the Detection of Prohibited Meat and Bone Meal Residues in Animal Feed

ABSTRACT: A unique biomarker, h-caldesmon, was identified and purified from bovine intestine smooth muscle. It was used to develop monoclonal antibodies (MAbs) for use in immunochemical assays to detect prohibited meat and bone meal (MBM) in animal feed. This biomarker with a molecular weight of 150 kDa was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to be present in MBM samples that were obtained from different manufacturers. The presence of this biomarker in MBM and smooth muscle was also demonstrated by immunostaining with MAb 8B4 in Western blot assay. h-Caldesmon in intestinal smooth muscle was demonstrated to be stable after autoclaving at 130 °C for up to 1 h. Because MAb 8B4 was sensitive in detecting MBM in animal feed at >0.05%, it can be used in immunoassays for MBM detection.     

氨基甲酸酯类农药半抗原的设计与改造

本研究设计了一种针对氨基甲酸酯类农药半抗原的通用改造,制备了涕灭威和异丙威两种人工半抗原。通过分子模拟手段和制备鼠源多克隆抗体对半抗原改造效果进行评价。结果表明,最终涕灭威抗体效价为5.84×105,对涕灭威的IC₅₀为0.225 μg/mL,对涕灭威半抗原的交叉反应率为107.14%;异丙威抗体效价为4.1×105,对异丙威的IC₅₀为0.4 μg/mL,对异丙威半抗原的交叉反应率为105.26%。经该通用改造后的半抗原可以代替目标药物用于免疫分析方法的建立。     

Development of a Monoclonal Antibody-Based Enzyme-Linked Immunosorbent Assay for the Analysis of Diclazuril in Chicken Tissues

A highly sensitive and specific monoclonal antibody (Mab) against diclazuril was produced. The hapten with diclazuril coupled to diazotised 4-aminobenzoic acid was synthesized and conjugated to bovine serum albumin by the active ester method to form an immunogen for antibody generation. A novel diclazuril carboxymethyloxime derivative used in an ovalbumin conjugate was applied as a heterologous coating antigen and was expected to improve the immunoassay sensitivity. A sensitive and simple indirect competitive enzyme-linked immunosorbent assay (icELISA) based on the Mab for the determination of diclazuril was developed. Under the optimized conditions, the icELISA for diclazuril showed a half maximum inhibition concentration (IC₅₀) value of 1.8 ng/mL, with limit of detection of 0.24 ng/mL and negligible cross-reactivities with other coccidiostat compounds including toltrazuril, robenidine, nicarbazin, halofuginone, amprolium, monensin, and maduramycin. The icELISA was successfully applied to diclazuril residue analysis in spiked chicken tissues. The average recoveries, intra-assay, and inter-assay coefficients of variation were in a range from 77.6 to 103.7 %, 3.7 to 13.0 %, and 5.6 to 18.3 %, respectively.