The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Wilfred Chen - One of the best experts on this subject based on the ideXlab platform.
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An immunoassay for atrazine using tunable Immunosorbent.
Analytical biochemistry, 2003Co-Authors: Jae-young Kim, Ashok Mulchandani, Wilfred ChenAbstract:Abstract A novel, simple, economical, and environmentally friendly tunable Immunosorbent-based immunoassay for sensitive and selective determination of atrazine is reported. Tunable Immunosorbents consisting of a fusion between an elastin-like polypeptide made up of 77 repeating units of the pentapeptide VPGVG and a single-chain Fv of an anti-atrazine antibody were synthesized biologically and purified by temperature-triggered phase transition. A competitive immunoassay based on the competition of atrazine–horseradish peroxidase and atrazine was established with IC 50 and lower detection limit of 0.16 and 0.01 ppb, respectively. Excellent recoveries (mean values ranging between 92 and 104%) were demonstrated in simulated atrazine-contaminated water samples.
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Tunable Immunosorbents for the remediation of atrazine- and simazine-contaminated waters
2003Co-Authors: Wilfred Chen, Ashok MulchandaniAbstract:Author(s): Chen, Wilfred; Mulchandani, Ashok | Abstract: A novel, simple, economical, and environmental friendly tunable Immunosorbent-based immunoassay for sensitive and selective determination of atrazine is reported. Tunable Immunosorbents consisting of a fusion between an elastin-like polypeptide made up of 77 repeating units of the pentapeptide VPGVG and a single chain Fv of an anti-atrazine antibody was synthesized biologically and purified by temperature-triggered phase transition. A competitive immunoassay based on the competition of atrazine-HRP and atrazine was established with IC50 and lower detection limit of 0.16 and 0.01 ppb, respectively. Excellent recoveries (mean values ranging between 92 % and 104 %) were demonstrated in simulated atrazine-contaminated water samples.
Valerie Pichon - One of the best experts on this subject based on the ideXlab platform.
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Aptamer-based and Immunosorbents
Solid-Phase Extraction, 2020Co-Authors: Valerie PichonAbstract:Abstract In analyzing the compounds that may be present at very low levels of concentration in complex media, such as food, environmental, and biological fluids, the exploitation of the affinity and specificity of the antibodies for their antigen is possible by immobilizing them on a solid support. The resulting Immunosorbents allow an effective extraction of compounds of interest while eliminating the other components of the matrix. The objective is then to make the analysis more reliable in terms of quantifying the target analytes by eliminating the matrix effects. A similar potential can also be obtained by using aptamers, i.e., DNA or RNA sequences with high specificity toward the compounds. The objective of this chapter is to present the respective characteristics of the Immunosorbents and aptamer-based sorbents, also known as oligosorbents and their potential for the selective extraction of targeted compounds for the treatment of real samples.
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Immunosorbents in microextraction
Trends in Analytical Chemistry, 2019Co-Authors: Valerie Pichon, Audrey Combes, Nathalie DelaunayAbstract:Trace analysis of target compounds from complex samples requires often a step of purification and of preconcentration before the chromatographic separation. Immunoaffinity sorbents functionalized with antibodies specific to the molecule(s) of interest appear as powerful tools for their selective extraction to obtain more reliable and sensitive quantitative analysis. Indeed, the high specificity and affinity of the antigen-antibody interactions allow an efficient and selective clean-up with high enrichment factors. Considering the cost of antibodies, the miniaturization of these sorbents presents a large interest as it combines the advantages of the miniaturization such as the reduction of solvent consumption and the application of the devices to reduced sample volumes while keeping high enrichment factors with the high selectivity provided by the antibodies during the extraction process. The objective of this review is to present the developments proposed these last years in the field of microextraction methods involving antibodies.
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Development of Immunosorbents coupled on-line to immobilized pepsin reactor and micro liquid chromatography–tandem mass spectrometry for analysis of butyrylcholinesterase in human plasma
Journal of Chromatography A, 2017Co-Authors: Maud Bonichon, Audrey Combes, Charlotte Desoubries, Anne Bossée, Valerie PichonAbstract:Human butyrylcholinesterase (HuBuChE) has been widely used as a biomarker of exposure to organophosphorus (OPs) warfare agents. Indeed, intoxication by OPs can be proven by LC–MS/MS analysis of a specific HuBuChE nonapeptide on which OPs covalently bind. Therefore, we developed a fast, selective and sensitive on-line set-up for the analysis of HuBuChE from plasma that combines immunoextraction by anti-HuBuChE antibodies, pepsin digestion on Immobilized Enzyme Reactors (IMER) and microLC–MS/MS analysis of the target nonapeptide, FGESAGAAS. Two pepsin-based IMERs were prepared and characterized in terms of grafting and digestion yields and were coupled on-line to microLC–MS/MS analysis. In addition, Immunosorbents were prepared by covalent grafting of three anti-HuBuChE antibodies on CNBr-sepharose and epoxy-polymethacrylate supports and packed in precolumns. The best antibody grafting yields were obtained with sepharose-based supports, with grafting yields up to 98%. B2 18-5 monoclonal antibody grafted on sepharose led to the best Immunosorbent, with HuBuChE recovery close to 100%. The Immunosorbent was introduced upstream of the on-line digestion set-up and immunoextraction of HuBuChE was achieved in 14 min while digestion was performed in 20 min, allowing detection of the target nonapeptide in less than 1 h. The global recovery of the nonapeptide was higher than 42% using the best Immunosorbent with a RSD value lower than 7% (n = 3). Finally, the limit of quantification evaluated in plasma sample was 2 fmol of nonapeptide. This value, corresponding to 0.5 fmol of HuBuChE tetramer, is well below the average amount of HuBuChE tetramer in 50 μL of plasma (590 fmol).
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Molecularly imprinted polymers for selective extraction of analytes from biological samples.
Annale de Toxicologie Analytique, 2007Co-Authors: Florence Chapuis, Valerie PichonAbstract:The analysis of interest compounds from biological samples requires a procedure of pretreatment in order to preconcentrate the analytes and clean-up the matrix. Despite its attractive features, classical sorbents used in SPE retain analytes by non selective hydrophobic interactions that lead to a partial coextraction of interfering substances. So, sorbents displaying more selective interactions are powerful tools for the development of sensitive and more reliable methods. Immunoaffinity supports can be used to obtain a selective extraction. They are based on the immobilization of specific antibodies developed against the target analyte (Immunosorbent). Nevertheless, the cost and the time required to produce antibodies lead to the development of a new polymeric material: the Molecularly Imprinted Polymers (MIP). These supports possess molecular recognition sites designed for the analyte of interest. With performances similar to Immunosorbents in terms of selectivity, MIPs present a better thermic and chemical stability and the cost of synthesis is also reduced. Like Immunosorbents, their retention mechanism is based on molecular recognition. In most cases, the developed interactions during the extraction are non covalent like - hydrogen bondings, π π − or electrostatic interactions. The most common approach to the synthesis is the bulk polymerisation to obtain a monolithic polymer. MIPs for SPE can be conditioned in cartridges or directly integrated in the analytical system. Many applications have already highlighted the high potential of MIPs for the selective extraction of target compounds from biological samples.
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automated sample preparation with extraction columns by means of anti isoproturon Immunosorbents for the determination of phenylurea herbicides in water followed by liquid chromatography diode array detection and liquid chromatography atmospheric pre
Journal of Chromatography A, 1997Co-Authors: Imma Ferrer, Valerie Pichon, Marieclaire Hennion, Damia BarceloAbstract:Abstract The retention of five phenylurea herbicides (chlorotoluron, isoproturon, diuron, linuron and diflubenzuron) was evaluated by solid-phase extraction with an automated sample preparation (ASPEC) system using anti-isoproturon Immunosorbents. The extraction was carried out after the percolation of 50 ml of LC-grade water and groundwater samples spiked with a mixture of the five pesticides at the ppb level and then elution with 4 ml of a mixture of methanol–water (70:30, v/v) and 1 ml of LC-grade water. The recoveries obtained ranged from 16 to 97% indicating a good affinity of the polyclonal antibodies of the Immunosorbent for compounds with similar structures to the antigen pesticide isoproturon. An inter-laboratory study using Aquacheck certified samples was performed in order to validate the use of the Immunosorbent for the analysis of environmental water samples. For the groundwater samples the calibration curves were linear in the range between 1 and 3 μg/l for each compound using liquid chromatography with diode array detection (LC–DAD). The overall mean difference comparing the values obtained by this method and the real values given by Aquacheck varied between 1 and 22%. All samples were analyzed simultaneously by LC–DAD and liquid chromatography–atmospheric pressure chemical ionization mass spectrometry.
Isabelle Auger - One of the best experts on this subject based on the ideXlab platform.
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Autoantibodies to BRAF, a new family of autoantibodies associated with rheumatoid arthritis
Arthritis Research and Therapy, 2010Co-Authors: Colette Charpin, Marielle Martin, Nathalie Balandraud, Jean Roudier, Isabelle AugerAbstract:INTRODUCTION: BRAF (v raf murine sarcoma viral oncogene homologue B1) is a serine-threonine kinase involved in the mitogen-activated protein kinase (MAPK) signalling pathway, known to be implicated in the production of pro-inflammatory cytokines.We have observed that sera from rheumatoid arthritis (RA) patients recognize the BRAF's catalytic domain, which encompasses amino acids 416 to 766. Here, we identify peptide targets of anti-BRAF autoantibodies and test whether anti-BRAF autoantibodies may interfere with BRAF kinase activity.\n\nMETHODS: Anti-BRAF autoantibodies were detected by ELISA (enzyme-linked Immunosorbent assay) in the serum of RA patients and controls, using 40 overlapping 20mer peptides encompassing the catalytic domain of BRAF as Immunosorbents. To test whether autoantibodies to BRAF influence BRAF kinase activity, we developed an in vitro phosphorylation assay of MEK1 (mitogen extracellular regulated kinase), a major BRAF substrate. MEK1 phosphorylation by BRAF was tested in the presence of purified anti-BRAF autoantibodies from RA patients or control antibody.\n\nRESULTS: We found that one BRAF peptide, P25 (656 to 675), is specifically recognized by autoantibodies from RA patients. Of interest, anti-P25 autoantibodies are detected in 21% of anti-CCP (cyclic citrullinated peptides) negative RA patients. Anti-BRAF autoantibodies activate the in vitro phosphorylation of MEK1 mediated by BRAF.\n\nCONCLUSIONS: Anti-BRAF autoantibodies from RA patients preferentially recognize one BRAF peptide: P25. Autoantibody responses to P25 are detected in 21% of anti-CCP negative RA patients. Most anti-BRAF autoantibodies activate BRAF kinase activity.
Stephanie Descroix - One of the best experts on this subject based on the ideXlab platform.
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Advanced immunocapture of milk-borne Salmonella by microfluidic magnetically stabilized fluidized bed
Electrophoresis, 2018Co-Authors: Jana Srbova, Pavla Krulisova, Lucie Holubova, Iago Pereiro, Amel Bendali, Audrey Hamiot, Veronika Podzemna, Jan Macak, Bruno Dupuy, Stephanie DescroixAbstract:The success of microfluidic immunocapture based on magnetic beads depends primarily on a sophisticated microscale separation system and on the quality of the magnetic Immunosorbent. A microfluidic chip containing a magnetically stabilized fluidized bed (μMSFB), developed for the capture and on-chip amplification of bacteria, was recently described by Pereiro et al.. The present work shows the thorough development of anti-Salmonella magnetic Immunosorbents with the optimal capture efficiency and selectivity. Based on the corresponding ISO standards, these parameters have to be high enough to capture even a few cells of bacteria in a proper aliquot of sample, e.g. milk. The selection of specific anti-Salmonella IgG molecules and the conditions for covalent bonding were the key steps in preparing an Immunosorbent of the desired quality. The protocol for immunocapturing was first thoroughly optimized and studied in a batchwise arrangement, and then the carrier was integrated into the μMSFB chip. The combination of the unique design of the chip (guaranteeing the collision of cells with magnetic beads) with the advanced Immunosorbent led to a Salmonella cell capture efficiency of up to 99%. These high values were achieved repeatedly even in samples of milk differing in fat content. The rate of nonspecific capture of Escherichia coli (i.e. the negative control) was only 2%.
Michael O Gardner - One of the best experts on this subject based on the ideXlab platform.
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rapid hiv versus enzyme linked Immunosorbent assay screening in a low risk mexican american population presenting in labor a cost effectiveness analysis
American Journal of Obstetrics and Gynecology, 2005Co-Authors: Nora M Doyle, Judy Levison, Michael O GardnerAbstract:Objective Mother-to-child transmission of human immunodeficiency virus is the most common cause of pediatric human immunodeficiency virus in the United States; the Centers for Disease Control and Prevention recommendations endorse rapid human immunodeficiency virus testing for women with unknown viral status to quicken antiretroviral therapy. We compared the cost-effectiveness of Oraquick (Orasure Technologies, Bethlehem, Pa) rapid testing versus enzyme-linked Immunosorbent assay testing for a low-risk population of Mexican American women who are in labor. Study design Using decision analysis techniques, we tested 2 strategies: (1) testing with enzyme-linked Immunosorbent assay that was confirmed by Western blot and (2) testing with Oraquick rapid testing that was confirmed by Western blot. All seropositive parturients received zidovudine treatment in labor. The baseline assumptions were the incidence of human immunodeficiency virus in Mexican American mothers (0.05%), mother-to-child transmission with no treatment (25%), with treatment in labor (10%), sensitivity of enzyme-linked Immunosorbent assay (98%), positive predictive value of enzyme-linked Immunosorbent assay (10%), sensitivity/specificity of Oraquick rapid testing (99%/100%), positive predictive value of Oraquick rapid testing (83%-100%), sensitivity/specificity of Western blot (97%/99%), costs (enzyme-linked Immunosorbent assay [$5], Oraquick rapid testing [$15], Western blot [$25], zidovudine treatment [$76] for 12 hours labor, neonatal treatment [$2.50], lifetime treatment of human immunodeficiency virus–affected child [$194,250]). Sensitivity analyses were done over a wide range of assumptions that included the costs of tests, the sensitivity of Oraquick rapid testing, the positive predictive value of enzyme-linked Immunosorbent assay and Oraquick rapid testing, and the costs of treatments. Results Oraquick rapid testing was the preferred strategy at $98 spent per human immunodeficiency virus–negative child versus $491 for enzyme-linked Immunosorbent assay testing. Much of the cost of the enzyme-linked Immunosorbent assay strategy was due to the treatment of women and infants with false-positive tests. Sensitivity analysis over test costs, test sensitivity, and other variables found the analysis results to be robust. Threshold analysis revealed that, if the cost remained Conclusion In a low prevalence population, the universal use of Oraquick rapid testing is cost-effective because of the low rate of false-positive results, thus preventing the emotional and economic costs of unnecessary treatment for human immunodeficiency virus to the new mother and her family.
