Indirect Competitive Chemiluminescence Research Articles

Quantitative determination of prothioconazole in wheat grain, soybean, and pond water based on a polyclonal antibody.

Prothioconazole and its metabolite are considered a potential threat to human health and environmental safety. Thus, the development of a sensitive and rapid detection method for prothioconazole is crucial to ensure the safety of agricultural products. In this study, a new hapten of prothioconazole was designed and synthesized, and a selective polyclonal antibody with high affinity against prothioconazole was produced, which was obtained from immunized New Zealand white rabbits. Based on the polyclonal antibody, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and indirect competitive chemiluminescence enzyme immunoassay (ic-CLEIA) were developed for detecting prothioconazole pesticides. Under optimized experimental conditions, the limit of quantification (LOQ) values for ic-CLEIA and ic-ELISA were 1.8 and 10.7 ng mL-1, respectively. The results demonstrated that the sensitivity (LOQ) achieved by ic-CLEIA was more than five times higher compared to that obtained with ic-ELISA. In addition, the recoveries obtained by adding standard prothioconazole to wheat grain, soybean, and pond water samples were in the range of 81.9 to 104.7% for ic-ELISA and 89.0 to 118.0% for ic-CLEIA.

Preparation of monoclonal antibody and establishment of indirect competitive chemiluminescence enzyme immunoassay for sodium pentachlorophenolate

In this study, three haptens of sodium pentachlorophenolate (PCP-Na) were designed and synthesized, and the monoclonal antibody against PCP-Na with high specificity and affinity was successfully prepared. Based on this monoclonal antibody, a highly sensitive indirect competitive chemiluminescence enzyme immunoassay (ic-CLEIA) was developed for the determination of PCP-Na and its metabolite pentachlorophenol (PCP). The ic-CLEIA method based on optimal conditions showed that the half maximal inhibitory concentration (IC50), linear range (IC20-IC80) and the detection limit (LOD, IC10) for PCP-Na were 0.083 ng/mL, 0.0076–1.5111 ng/mL, and 0.0032 ng/mL, respectively, and 0.29 ng/mL, 0.0983–0.7008 ng/mL, and 0.0192 ng/mL for PCP, respectively. The results of cross reaction showed that the method had no obvious cross reaction with other six chlorophenols compounds (phenol, 2-chlorophenol, 4-chlorophenol, 2, 4-dichlorophenol, 2, 4, 5-trichlorophenol, 2, 4, 6-trichlorophenol) except the metabolite PCP. The average recoveries in chicken, pork and fish samples were 81.3–105.8 %, with coefficient of variation (CV) lower than 7.6 %. In this study, a new highly rapid, sensitive and accurate ic-CLEIA method was established, which can be used for the sensitive detection of PCP-Na and its metabolite PCP in animal tissues.

A Chemiluminescence Enzyme Immunoassay Based on Biotinylated Nanobody and Streptavidin Amplification for Diazinon Sensitive Quantification

The advantages of genetic modification and preferable physicochemical qualities make nanobody (Nb) easy to develop a sensitive and stable immunosensor platform. Herein, an indirect competitive chemiluminescence enzyme immunoassay (ic-CLEIA) based on biotinylated Nb was established for the quantification of diazinon (DAZ). The anti-DAZ Nb, named Nb-EQ1, with good sensitivity and specificity, was obtained from an immunized library via a phage display technique, where the molecular docking results indicated that the hydrogen bond and hydrophobic interactions between DAZ and complementarity-determining region 3 and framework region 2 in Nb-EQ1 played a critical role in the Nb-DAZ affinity processes. Subsequently, the Nb-EQ1 was further biotinylated to generate a bi-functional Nb-biotin, and then an ic-CLEIA was developed for DAZ determination via signal amplification of the biotin–streptavidin platform. The results showed that the proposed method based on Nb-biotin had a high specificity and sensitivity to DAZ, with a relative broader linear range of 0.12–25.96 ng/mL. After being 2-folds dilution of the vegetable samples matrix, the average recoveries were 85.7–113.9% with a coefficient of variation of 4.2–19.2%. Moreover, the results for the analysis of real samples by the developed ic-CLEIA correlated well with that obtained by reference method GC-MS (R2 ≥ 0.97). In summary, the ic-CLEIA based on biotinylated Nb-EQ1 and streptavidin recognition demonstrated itself to be a convenient tool for the quantification of DAZ in vegetables.

Production of high affinity monoclonal antibody and development of indirect competitive chemiluminescence enzyme immunoassay for gentamicin residue in animal tissues

To determine gentamicin residues in animal tissues, a monoclonal antibody (Mab) was produced and a sensitive indirect competitive chemiluminescent enzyme immunoassay (icCLEIA) was developed. At first, gentamicin was conjugated with bovine serum albumin as immunogens which were used to immunize BALB/c mice. Then, an anti-gentamicin Mab was prepared by hybridoma technology. Finally, a sensitive icCLEIA was developed with an 50% inhibition concentration (IC50) of 0.067 ng/mL for gentamicin. The limit of detection of the icCLEIA was 0.002 ng/mL. The cross reactivity of the Mab with structural analogues were<0.01%. The recoveries of gentamicin ranged from 80 to 101% and coefficient of variation was <6.4% in pork and fish samples. Samples were detected by UPLC-MS/MS for evaluating reliability of the icCLEIA. The results suggested that the prepared anti-gentamicin Mab can be used for rapid and convenient immunoassays to detect gentamicin residues in animal tissues.

Determination of Acetamiprid Residues in Vegetables by Indirect Competitive Chemiluminescence Enzyme Immunoassay.

Acetamiprid (ACE) is widely used in various vegetables to control pests, resulting in residues and posing a threat to human health. For the rapid detection of ACE residues in vegetables, an indirect competitive chemiluminescence enzyme immunoassay (ic-CLEIA) was established. The optimized experimental parameters were as follows: the concentrations of coating antigen (ACE-BSA) and anti-ACE monoclonal antibody were 0.4 and 0.6 µg/mL, respectively; the pre-incubation time of anti-ACE monoclonal antibody and ACE (sample) solution was 30 min; the dilution ratio of goat anti-mouse-HRP antibody was 1:2500; and the reaction time of chemiluminescence was 20 min. The half-maximum inhibition concentration (IC50), the detection range (IC10–IC90), and the detection limit (LOD, IC10) of the ic-CLEIA were 10.24, 0.70–96.31, and 0.70 ng/mL, respectively. The cross-reactivity rates of four neonicotinoid structural analogues (nitenpyram, thiacloprid, thiamethoxam, and clothianidin) were all less than 10%, showing good specificity. The average recovery rates in Chinese cabbage and cucumber were 82.7–112.2%, with the coefficient of variation (CV) lower than 9.19%, which was highly correlated with the results of high-performance liquid chromatography (HPLC). The established ic-CLEIA has the advantages of simple pretreatment and detection process, good sensitivity and accuracy, and can meet the needs of rapid screening of ACE residues in vegetables.

A novel high-sensitive indirect competitive chemiluminescence enzyme immunoassay based on monoclonal antibody for tenuazonic acid (TeA) detection

A novel high-sensitive indirect competitive chemiluminescence enzyme immunoassay based on monoclonal antibody for tenuazonic acid (TeA) detection

Simultaneous detection of CA15-3 and PGRMC1 on a microfluidic chip for early diagnosis of breast cancer

Simultaneous, rapid, and quantitative detection of multiple tumor markers is extremely important for the prevention and early diagnosis of cancers. In this study, we established a microfluidic-based indirect competitive chemiluminescence enzyme immunoassay for simultaneous detection of cancer antigen 15-3 (CA15-3) and progesterone receptor membrane components 1 (PGRMC1) for diagnosis of breast cancer. CA15-3 and PGRMC1 could be simultaneously detected on the chip. On the chip, the linear ranges of CA15-3 and PGRMC1 were 10 pg/mL–100 ng/mL and 20 pg/mL–358 ng/mL, respectively, whereas the limits of detection (LOD) of CA15-3 and PGRMC1 were 3 pg/mL and 5 pg/mL, respectively. Compared with the enzyme-linked immunosorbent assay (ELISA, LOD = 20 pg/mL for CA15-3; LOD = 10 pg/mL for PGRMC1), our method could simultaneously detect multiple samples with higher sensitivity, which could greatly improve the detection efficiency and meet the requirement for early diagnosis of breast cancer.

Indirect Competitive Chemiluminescence Immunoassay for Glycosides Daidzin and Genistin in Soy Products

Daidzin (DZ) and genistin (GEN) are the main glucosidic components of soy isoflavone; the detection of DZ and GEN can provide insight for the appropriate ingestion of soy products. An indirect competitive chemiluminescence immunoassay (icCLIA) method based on N-(aminobutyl)-N-(ethylisoluminol) (ABEI) as chemiluminescent (CL) label was developed to assay DZ in soy products. Meanwhile, GEN also could be determined due to the cross reaction with DZ monoclonal antibody (MAb). Fluorescein isothiocyanate (FITC) was used to label the pure DZ antigen to compete with DZ in toy products. Magnetic beads (MBs) capped with anti-FITC antibody were both the solid phase and separator. The chemiluminescence signal produced by the emission of photons from ABEI was inversely proportional to the amount of DZ and GEN in the sample solution. The method was linear to 6000 ng/mL DZ with a detection limit of 1.34 ng/mL. The intra-assay imprecision results [mean (coefficient of variation, CV)] were less than 6%. The average recoveries ranged from 92 to 98%. The relationship between the proposed method and high-performance liquid chromatography (HPLC) exhibited a correlation. The proposed method demonstrates acceptable performance for rapid quantification of DZ and GEN and can be used to rapidly detect these substances in soy products.

Magnetic nanoparticles-phenanthrene conjugates (MNPs-Phe) probe based competitive chemiluminescence enzyme immunoassay (MNPs-icCLEIA) for phenanthrene and other homologous polycyclic aromatic hydrocarbons

In this study, a magnetic nanoparticle-phenanthrene hybrid conjugates (MNPs-Phe) probe was synthesized and an indirect competitive chemiluminescence enzyme immunoassay (MNPs-icCLEIA) was developed for rapid and sensitive detection of phenanthrene (Phe) and its homolog in water samples. The developed MNPs-icCLEIA was based on competitive reaction between Phe in samples and the MNPs-Phe probe. In the presence of Phe, the monoclonal antibody (McAb) would be competitive captured by MNPs-Phe probe and Phe in samples. Then MNPs-Phe-McAb complexes would be separated by a magnetic field. After the reaction of horseradish peroxidase conjugated goat anti-mice IgG (HRP-IgG) with MNPs-Phe-McAb complexes, chemiluminescent substrate was added and chemiluminescence was produced. The linear range of the assay for Phe was from 1.85 to 71.51ngmL−1 and the limit of detection (LOD) was 0.85ngmL−1. Compared with the traditional enzyme linked immunosorbent assay (ELISA), the sensitivity of the developed MNPs-icCLEIA was about 3 times higher and more than 90min was saved to fulfill the procedure of developed method while the linear range was nearly the same. The recoveries of polycyclic aromatic hydrocarbons (PAHs) from three different water samples were 97.2%–103.4%, 95.8%–104.8% and 96.9%–103.5% respectively, which had a good correlation (R2=0.9986) with those from ELISA. The results indicated that the developed MNPs-icCLEIA is sensitive, rapid and reliable for the detection of Phe and other homologous PAHs in environmental water.

An Improved Chemiluminescence Immunoassay for the Ultrasensitive Detection of Aflatoxin B1

An indirect competitive chemiluminescence (CL) immunoassay based on Fe3O4@SiO2@Au magnetic nanoparticles (Au-SCMPs) has been optimized and developed for the detection of aflatoxin B1 (AFB1). To improve the detection sensitivity and efficiency, this method combines 2′,6′-dimethylcarbonylphenyl-10-sulfopropyl acridinium-9-carboxylate 4′-NHS ester (NSP-DMAE-NHS) as a new kind of high efficient luminescence reagent with a simplified separation procedure based on the optimized Au-SCMPs. Superparamagnetic nanoparticles were coated with different sizes of Au colloids (18, 30, and 50 nm), and their capacities in immobilization of bovine serum albumin (BSA) were investigated. The BSA-AFB1 conjugate (BSA-AFB1) was immobilized on the optimized Au-SCMPs and competed with the free AFB1 for specially binding the NSP-DAME-NHS-labeled anti-AFB1 antibody (mAb-AFB1). After the indirect competitive immunoreactions and magnetic separation, the CL of the nanoparticles was measured by a homemade luminescent measurement system. Under the optimum conditions, the IC50 value was 0.07 ng mL−1 and the limit of detection (LOD) of AFB1 was 0.01 ng mL−1, respectively. The result shows a much lower IC50 and LOD than that typically achieved by ELISA. This proposed immunoassay method was rapid, low-cost, and suitable for the detection of AFB1.

Broad-Specificity Chemiluminescence Enzyme Immunoassay for (Fluoro)quinolones: Hapten Design and Molecular Modeling Study of Antibody Recognition.

On the basis of the structural features of (fluoro)quinolones (FQs), pazufloxacin was first used as a generic immunizing hapten to raise a broad-specificity antibody. The obtained polyclonal antibody exhibited broad cross-reactivity ranging from 5.19% to 478.77% with 21 FQs. Furthermore, the antibody was able to recognize these FQs below their maximum residue limits (MRLs) in an indirect competitive chemiluminescence enzyme immunoassay (ic-CLEIA), with the limit of detection (LOD) ranging from 0.10 to 33.83 ng/mL. For simply pretreated milk samples with spiked FQs, the ic-CLEIA exhibited an excellent recovery with a range of 84.6-106.9% and an acceptable coefficient of variation below 15%, suggesting its suitability and reliability for the use of a promising tool to detect FQs. Meanwhile, comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) models, with statistically significant correlation coefficients (q(2)CoMFA = 0.559, r(2)CoMFA = 0.999; q(2)CoMSIA = 0.559, r(2)CoMSIA = 0.994), were established to investigate the antibody recognition mechanism. These two models revealed that in the antibody, the active cavity binding FQs' 7-position substituents worked together with another cavity (binding FQs' 1-position groups) to crucially endow the high cross-reactivity. This investigation will be significant for better exploring the recognition mechanism and for designing new haptens.

Establishment of Enhanced Chemiluminescent Immunoassay Formats for Stanozolol Detection in animal-derived foodstuffs and Other Matrices

Stanozolol is one of the most widely used synthetic anabolic steroids but also presents a host of negative side effects. It is necessary to develop a rapid and sensitive method for stanozolol screening to monitor its abuse. In this study, the polyclonal antibody against stanozolol was prepared and a novel indirect competitive chemiluminescence enzyme immunoassay (CLEIA) for stanozolol was developed. The stanozolol hapten was conjugated to proteins to prepare immunogen and coating antigens, firstly. To improve the performances of the method, the chemiluminescent detection system was optimized. The optimal concentration of 4-iodophenol, hydrogen peroxide and luminol was studied and the proper detection time was also investigated. Under the optimal conditions, the IC50 value and the limit of detection (IC20) of the chemiluminescence immunoassay is 0.34 and 0.07 ng/mL in phosphate-buffered saline (PBS), respectively. The accuracy performances of the proposed CLEIA were compared with that of ELISA and HPLC. Different nutraceuticals, foodstuffs, and biological matrices spiked with stanozolol were applied to study the application of the proposed assays, and the average recoveries locate at 92–113 % with the coefficients of variation of 8–13.5 %. The polyclonal antibody-based chemiluminescence immunoassay formats are proved to be a feasible and reliable quantificational method for stanozolol.

Determination of Furaltadone Metabolite in Fish by Chemiluminescence Enzyme Immunoassay

Abstract An indirect competitive chemiluminescence enzyme immunoassay (icCLEIA) detection for the furaltadone metabolite 5-morpholinomethyl-3-amino-2-oxazolidone (AMOZ) was established. The effects of the coating antigen concentration, antibody dilution, immunoreaction time, reaction buffer and its ion concentration on the performance of the assay were studied and optimized. The results showed that the optimized assay conditions were as follows: the coating antigen concentration was 10 ng mL−1, the polyclonal antibody was diluted 60000 times, immunoreaction time was 50 min and the buffer solution was 0.01 M phosphate buffer solution (PBS, pH 7.4). Under the optimized conditions, the linear detection range of the developed icCLEIA was 0.026–3.52 μg L−1, the half inhibitory concentration (IC50) was 0.29 μg L−1 and the limit of detection (IC10) was 0.012 μg L−1. The average recoveries of AMOZ of spiked fish ranged from 101.0% to 115.5%. In conclusion, the icCLEIA is applicable for detection of trace AMOZ in fish samples.

Bisphenol A determination in baby bottles by chemiluminescence enzyme-linked immunosorbent assay, lateral flow immunoassay and liquid chromatography tandem mass spectrometry

Two immunoassays, a Lateral Flow ImmunoAssay (LFIA) based on colloidal gold nanoparticle labels and an indirect competitive chemiluminescence enzyme-linked immunosorbent assay (CL-ELISA), were developed and a high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was optimized to assess the possible release of bisphenol A (BPA, 4,4'-isopropylidenediphenol) from different plastic baby bottles treated with simulating solutions. Coating conjugate concentration, anti-BPA antibody dilution, incubation time of the primary and secondary antibodies, and tolerance to different organic solvents were optimized to obtain the best performance of the ELISA with chemiluminescent end-point detection. The influence of different buffers on LFIA performance was also evaluated. Both methods showed good repeatability (mean CV value around 13%) and sensitivity. Reproducibility tests for CL-ELISA gave a mean CV value of about 25%. The IC50 and Limit of Detection (LOD) values of CL-ELISA were 0.2 and 0.02 ng mL(-1), respectively. The LOD of LFIA was 0.1 μg mL(-1). A LC-MS/MS method was also optimized. The separation was performed in a C18 column with a triple-quadrupole mass spectrometer with electrospray ionisation interface. The method showed a good linearity in the range 2 to 500 ng mL(-1), with a regression coefficient of 0.998. In the simulating solutions the detection and quantification limits, calculated by the signal to noise level of 3 (S/N = 3), were 5.8 ng mL(-1) and 17.4 ng mL(-1), respectively. This limit of quantification was about 3 and 35 times lower than the permitted limits set by the official method CEN/TS 13130-13 (0.05 μg mL(-1)) and by the Directive 2004/19/EC (0.6 μg mL(-1)), respectively. The methods were applied to determine BPA release from baby bottles, performing repeated procedures according to EU and national regulations. The results demonstrated that no BPA migration from the tested plastic materials occurred with only one exception. The migrated amount, above the regulatory limits, was detected by all the mentioned assays.

Development of an Ultra-sensitive Chemiluminescence Enzyme Immunoassay for the Determination of Diethylstilbestrol in Seafood

An ultra-sensitive indirect competitive chemiluminescence enzyme immunoassay was developed for screening diethylstilbestrol in fish and shrimp samples. The concentration of diethylstilbestrol that caused 50% inhibition of the binding enzyme marker (IC50) was 0.32 ng/mL and the limit of detection was 0.0068 ng/mL; the linear range was from 0.028 ng/mL to 3.60 ng/mL. The assay showed cross-reactivity of 7.1% and 2.8% with dienestrol and hexoestrol, respectively, but negligible cross-reactivity with estradiol, estrone, ethinyloestradiol, and progestin. The recovery from spiked fish and shrimp samples varied from 68.5% to 92.5%, and the mean coefficients of variation within groups and between groups were 6.2% and 8.0%, respectively. Our results indicated that the assay is a simple, sensitive, specific, and accurate method for screening fish and shrimp samples for diethylstilbestrol.

Development of an Indirect Competitive Chemiluminescence Enzyme-linked Immunoassay for Parathion

Polyclonal antibody(PcAb) against parathion was raised and used to develop an indirect competitive chemiluminescence enzyme-linked immunoassay(icCLEIA).The hapten was prepared from thiophosphoryl chloride after a three-step substitution reaction.The hapten was coupled to bovine serum albumin(BSA) and ovalbumin(OVA) as immounogen and coating antigen respectively by active ester method.New Zealand rabbits were immunized by the immunogen to obtain anti-parathion polyclonal antibody.Several parameters that might affect icCLEIA performance were carefully optimized.Under the optimum conditions,the linear range of the developed icCLEIA was 0.24-15.83 μg/L,the IC50 was 1.14 μg/L and the limit of detection was 0.09 μg/L.The average recovery of parathion from spiked vegetables and water samples ranged from 74.6% to 121.0%.In conclusion,the icCLEIA is a practical method for trace detection of parathion in real samples.

Indirect Competitive Chemiluminescence Enzyme Immunoassay for Furaltadone Metabolite in Metapenaeus Ensis

Abstract An indirect competitive chemiluminescence enzyme immonoassay (icCLEIA) for the quantitative analysis of furaltadone metabolite 5-morpholinomethyl-3-amino-2-oxazolidone(AMOZ) in Metapenaeus ensis sample was established with the highly sensitive luminol-H 2 O 2 -HRP-4-iodophenol chemiluminescence reaction detection system. The icCLEIA method was based on a single-chain variable fragment (scFv) antibody against AMOZ derivative. The optimized assay conditions were as follows: 62.5 μg L −1 of coating antigen (5-morpholinomethyl-3-(glyoxalamino)-2-oxazolidone-ovalbumin, AMOZA-OVA) was used in the experiment, the dilute multiple of scFv antibody was 1:10, the immunoreaction time was 45 min, and the dilute multiple and incubation time of HRP-goat anti mouse IgG were 1:10000 and 50 min, respectively. The icCLEIA results showed that IC 50 value and limit of detection (LOD) were 1.38 μg L −1 and 0.09 μg L −1 , and linear range was in the range of 0.26–9.1 μg L −1 . Inter-assay and intra-assay RSD were both below 15%. The scFv antibody showed high specificity. The average recoveries of four spiked level of AMOZ were 72.2%, 73.4%, 72.6% and 78.6%, respectively. In comparison with HPLC-MS/MS, there was a good correlation between the two methods ( R 2 = 0.9997). The established icCLEIA method could be further used for detecting AMOZ in aquatic products samples rapidly and efficiently.

Cloning, expression, purification, and characterization of a novel single-chain variable fragment antibody against the 2-nitrobenzaldehyde derivative of a furaltadone metabolite in Escherichia coli

Furaltadone is an illicit veterinary drug that shows toxic, carcinogenic, and mutagenic effects, as does its metabolite 3-amino-5-morpholinomethyl-2-oxazolidone (AMOZ)1Abbreviations used: scFv, single-chain variable fragment; AMOZ, 3-amino-5-morpholinomethyl-2- oxazolidone; NPAMOZ, 2-nitrobenzaldehyde derivative of furaltadone metabolite 3-amino-5-morpholinomethyl-2-oxazolidone; VH, heavy chain variable region; VL, light chain variable region; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; Ni-NTA, nickel nitrilotriacetic acid; icCLEIA, indirect competitive chemiluminescence enzyme immunoassay; PAb, polyclonal antibody; MAb, monoclonal antibody; RAb, recombinant antibody; PCR, polymerase chain reaction; IPTG, isopropyl β-d-1-thiogalactopyranoside; RLU, relative light units.1. Recombinant antibodies with desirable affinity and specificity that can replace polyclonal or monoclonal antibodies are important factors for effective AMOZ immunoassays. In the present study, a novel single-chain variable fragment (scFv) antibody against the 2-nitrobenzaldehyde derivative of AMOZ (NPAMOZ) was prepared and characterized. The scFv gene was cloned into the pET-22b(+) expression vector, and 6His-tagged scFv antibodies expressed as inclusion bodies in Escherichia coli BL21 (DE3), which were then purified by nickel nitrilotriacetic acid column chromatography. Characterization of the target protein by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), western blotting, and a novel indirect competitive chemiluminescence enzyme immunoassay (icCLEIA) showed that the scFv antibody was ∼27kDa and exhibited HRP-anti-His-tag antibody-recognized activity. The final purity, yield and mg of this scFv antibody after ultrafiltration concentration were 97%, 20% and 29.1mg, respectively. The icCLEIA indicated that the antibody competitively combined with NPAMOZ, exhibiting an IC50 value of 1.46±0.01ng/ml (n=6). Cross-reactivity studies revealed that the antibody showed desirable specificity to NPAMOZ and little reactivity to analogs except the parent furaltadone. In summary, these findings suggested that the prepared recombinant scFv antibody can be used for future immunoassay screening for AMOZ.

Chemiluminescent ELISA for the BTEX Determination in Water and Soil

An indirect competitive chemiluminescence enzyme-linked immunosorbent assay (CL-ELISA) for the determination of benzene, toluene, ethylbenzene, and ortho-, meta-, para-xylenes (BTEX) in soil and water was developed. The assay was optimized concerning the coating conjugate concentration, anti-BTEX antiserum dilution, incubation time effect on primary and secondary antibody incubation, and temperature effect on the competitive step and tolerance to different organic solvents. The IC(50) and lower limit of the detection (LDD(90)) values were 4.6 and 0.5 microg mL(-1), respectively. While water samples could be analyzed directly, soil has to be extracted and diluted prior to immunochemical measurements. BTEX could be recovered from spiked soil with a yield higher than 60% using 5-min ultrasonication with methanol. Finally, the assay was applied to soil and water samples collected at a contaminated site in Italy, and was compared to GC-MS.

A regenerable immunochip for the rapid determination of 13 different antibiotics in raw milk

Access to high-quality and safe food is a basic need in our community and, consequently, the European Union has defined maximum residue levels (MRLs) for a number of antibacterial compounds. However, despite the obvious demand for quantitative multi-residue detection methods that can be carried out on a routine basis, there is currently a lack in the development of such systems. In particular, an automated multianalyte detection instrument is needed that is capable of quantifying several antibiotics simultaneously within minutes. The newly developed hapten microarrays are designed for the parallel analysis of 13 different antibiotics in milk within six minutes by applying an indirect competitive chemiluminescence microarray immunoassay (CL-MIA). To allow multiple analyses, a regenerable microarray chip was developed based on epoxy-activated PEG chip surfaces, onto which microspotted antibiotic derivatives like sulfonamides, beta-lactams, aminoglycosides, fluorquinolones and polyketides are coupled directly without further use of linking agents. Using the chip reader platform MCR 3, this antigen solid phase is stable for at least 50 consecutive analyses.