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Melatonin (MT) is a hormone secreted by the pineal gland which regulates sleep rhythm and is widely used in health foods. However, MT is sometimes added illegally and excessively in certain health foods, which might cause undesirable side-effects. In this work, an easy-to-use immunochromatographic assay (ICA) based on mouse monoclonal antibody (mAb) for rapid detection of MT was developed for the purpose of safety. Under the optimal conditions, the developed ICA exhibited a visual limit of detection (VLOD) of 10,000 ng/mL and a LOD of 50 ng/mL (strip reader) with the linear range from 50 ng/mL to 5000 ng/mL. Good correlation was obtained between the results of ICA and standard liquid chromatography (LC) in matrix test and blind samples test. The developed ICA can be applied for rapid detection of samples within 30 min, and is potentially an excellent tool for screening of MT in health foods. [ABSTRACT FROM AUTHOR]

In this work, a rapid, convenient and sensitive Au nanoparticle-based immunochromatographic sensor (AuNPs-ICS) for simultaneous detection of various tadalafil adulterants in health food was established for the first time, based on one high affinity and broad-spectrum antibody through skeleton-specific hapten design according to the common structure of tadalafil drugs. This immunochromatographic sensor was developed by the polyclonal antibody conjugated with AuNPs and the IC50 was 10.04 ng mL−1 for tadalafil and 9.55, 11.46, 17.01 ng mL−1 for amino tadalafil, acetamino tadalafil and nortadalafil, respectively. The limit of detection results could be obtained visually by naked eyes for and computationally by the hand-held immunochromatography reader. The sensor could specially detect Tadalafil and its analogs within 10 min in health food samples, and the close correlation with UPLC-MS/MS method showed the sensor was accurate and reliable, which could apply to on site detection Tadalafil and its analogs rapidly and accurately. [ABSTRACT FROM AUTHOR]

In this study, dehydroepiandrosterone (DHEA) hapten and high sensitivity polyclonal antibody against DHEA were prepared, a competitive indirect enzyme-linked immunosorbent assay (ciELISA) and lateral flow immunochromatography (LFA) for the determination of DHEA in slimming products were developed for the first time. The sample pretreatment was very simple and fast, the limit of detection (LOD) of the ciELISA for DHEA in slimming products was 9.6 μg/kg. The average recoveries of slimming tea, slimming tablets and slimming capsules ranged from 93.2% to 99.4%, 86.8% to 100.0%, and 80.5% to 115.4%, respectively, with the coefficient of variations (CVs) between 7.7% and 14.1%, 2.7% and 11.0%, and 2.2% and 8.6%, respectively. The pAb had negligible cross-reactivity to the structural and functional analogs of DHEA. Simultaneously, the LFA showed a cut-off value of 500 μg/kg in slimming products, and the results could be attained within 3 min. A parallel HPLC analysis in 30 commercial slimming products validated a good agreement with the proposed ciELISA and LFA. [ABSTRACT FROM AUTHOR]

Immunoassay direct for 3-amino-5-morpholinomethyl-2-oxazolidone (AMOZ), the metabolite of furaltadone, based on a specific antibody was usually unavailable due to its small molecule weight. In this work, a hapten with a double bond and an active carboxyl group was designed and then conjugated to peptide dendrimer to obtain novel multiple haptens. The haptens and multiple haptens were coupled to bovine serum albumin as immunogens. Polyclonal antibodies showed binding to free AMOZ in a heterologous competitive indirect enzyme-linked immunosorbent assay were obtained. The assay showed IC50 (half maximal inhibitory concentration) of 4.1 μg/kg and limit of detection of 0.2 μg/kg for AMOZ. Recoveries of AMOZ from grass carp were tested from 83.1% to 117.0%, with the coefficient of variation below 12%. As no laborious derivatisation procedure was employed, the proposed assay should be useful for the screening of AMOZ for a large number of samples. [ABSTRACT FROM AUTHOR]

Phthalate acid esters (PAEs) contamination raised concerns as a result of migration from food packaging and environmental exposure. Because of the adverse effects of PAE reported in humans, the aim of this study was to examine the ability to screen for the detection these chemicals as an indicator of potential exposure. Too develop a sensitive screening test to determine PAE, a specific polyclonal antibody against phthalic acid (PA), the hydrolysate of PAEs, was used as a marker of total PAEs. This method involved the use of 4-aminophthalic acid (APA) as an immunizing hapten to generate antibody. Subsequently, this antibody conjugated with labeled gold nanoparticles (GNPs) was then used to develop an immunochromatographic assay (ICA) for visually detecting PA. After establishing optimal assay conditions, the ICA strip detected visually PA at 3 μg/ml rapidly in less than 5 min. Further, this assay exhibited reliable specificity for PA with no apparent cross-reactivity with structurally related PAEs. A significant correlation between data obtained with the ICA strip and high-performance liquid chromatography (HPLC) analysis was achieved using cooking oils as model spiked samples. The proposed use of ICA offers an effective tool for rapid on-site screening for total PAEs in cooking oils. [ABSTRACT FROM AUTHOR]

To produce specific antibodies against leuco-malachite green (LMG), 15 haptens were synthesized and characterized, and conjugated to carrier protein for immunization. One antigen with excellent reactogenicity and immunogenicity was discovered. Specific monoclonal antibody with high sensitivity for LMG in competitive indirect enzyme-linked immunosorbent assay (ciELISA) was screened and selected. After the screening of a series of heterologous coating antigen and optimization of working conditions, the proposed ciELISA showed the 50% inhibition value (IC50) of 1.16 ng mL−1and the limit of detection of 0.06 ng mL−1for LMG. The average recoveries of LMG from spiked fish samples ranged from 78.0% to 101.0%, with coefficients of variation below 15%. Good correlation (R2 = 0.9977) was obtained between the results of ciELISA analysis and those of standard liquid chromatography–tandem mass spectrometry analysis. The proposed ciELISA is ideal for the rapid and sensitive detection of LMG with a low cost and high throughput. [ABSTRACT FROM PUBLISHER]

A simple, rapid and cost-effective QuEChERS method for the determination of ZEN and DON by ELISA in cereals was developed. The single factor experiment was used to find the optimal QuEChERS parameters (extraction solvent, extraction method, extraction time, the QuEChERS composition, sorbent and clarification time) and extracts were analysed by ELISA. The optimised method was validated for selectivity, linearity, limits of detection, matrix effect and precision. The recovery values of ZEN and DON by ELISA were compared with a standard HPLC method and the results showed good coefficient with HPLC, which proved to be suitable for the screening of cereal samples for the presence of ZEN or DON. This is the first report of the determination of ZEN and DON in cereals after QuEChERS extraction combined with the enzyme-linked immunosorbent assay method. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A rapid, specific, and sensitive fluorescence polarization immunoassay (FPIA) method was developed to detect residues of furazolidone, a forbidden drug in feed. An immuno-hapten was designed for monoclonal antibody preparation. Furthermore, seven novel tracers were synthesized and the 'heterology tracer' could improve the sensitivity of FPIA significantly. An optimized FPIA method was established with a cross-reactivity of less than 0.1%, IC50 of 5.5 ng/mL. The limits of detection (LOD) calculated from feed samples were 0.5-0.9 ng/mL. Recoveries of fortified samples at levels of 5, 20, and 50 ng/mL ranged from 79.0% to 85.0%. The coefficients of variation were less than 12%. [ABSTRACT FROM AUTHOR]