Rapid Fluorescence Polarization Immunoassay Research Articles

A Robust Homogeneous Fluorescence Polarization Immunoassay for Rapid Determination of Erythromycin in Milk.

Erythromycin (ERY) is one of the most common macrolides applied in veterinary medicine to treat diseases or as a feed additive for animal growth promotion. Long-term irrational use of ERY could lead to residues in animal-derived food and the emergence of drug-resistant strains, posing potential threats to human health. In this study, a highly sensitive, specific, robust, and rapid fluorescence polarization immunoassay (FPIA) for the determination of ERY in milk has been described. Herein, to achieve high sensitivity, five tracers of ERY with different fluorescein structures were synthesized and paired with three monoclonal antibodies (mAbs). Under the optimized conditions, the combination of mAb 5B2 and tracer ERM-FITC achieved the lowest IC50 value in the FPIA with 7.39 μg/L for ERM. The established FPIA was used to detect ERY in milk, revealing a limit of detection (LOD) of 14.08 μg/L with recoveries of 96.08-107.77% and coefficients of variations (CVs) of 3.41-10.97%. The total detection time of the developed FPIA was less than 5 min from the addition of samples to the result readout. All the above results showed that the proposed FPIA in this study was a rapid, accurate, and simple method for the screening of ERY in milk samples.

Determination of Nicotinic Acid in Food and Pharmaceuticals by a Simple and Rapid Fluorescence Polarization Immunoassay (FPIA)

A simple and rapid fluorescence polarization immunoassay (FPIA) based on polyclonal antibodies is reported for the first time for the determination of nicotinic acid. First, six nicotinic acid analogues were coupled with fluorescein isothiocyanate isomer I (FITC) to obtain tracers. The influences of tracer structure on the performance of FPIA as well as the structure-activity relationships were explored. Subsequently, the tracer concentration and antibody dilution ratio on the performance of FPIA were investigated. For the optimal conditions, the detection range of FPIA was from 1.1 to 145.6 μg mL−1 and its IC20 value as the limit of detection (LOD) was 1.1 μg mL−1. The cross-reactivity of antibodies with common vitamins was evaluated. The intra-assay recovery was from 92.0% to 101.2% in food and tablets, with inter-assay recoveries between 92.0% and 103.8%. The developed FPIA provided good sensitivity and reproducibility and therefore provided efficient and economic screening for nicotinic acid in food and tablets.

Development of a sensitive and rapid fluorescence polarization immunoassay for high throughput screening eight glucocorticoids in beef

In this study, a sensitive, rapid, homogeneous, and high-throughput fluorescence polarization immunoassay (FPIA) for the rapid screening of eight glucocorticoids (GCs) in beef samples was successfully established. Two tracers including 5-aminofluorescein-labeled dexamethasone (5-AF-DMS) and fluorescein isothiocyanate-labeled dexamethasone (FITC-DMS) were studied to select appropriate antibody-tracer pairs using four previously produced broad-specific monoclonal antibodies. An optimal combination of the antibody 12D9 and the tracer FITC-DMS was selected. Under optimal detection conditions, the half inhibitory concentrations of dexamethasone (DMS), betamethasone (BMS), prednisolone (PNS), hydrocortisone (HCS), beclomethasone (BCMS), cortisone (CS), 6-α-methylprednisone (6-α-MPNS), fludrocortisone acetate (HFCS) were 1.00, 2.17, 3.49, 12.45, 1.20, 5.66, 6.85 and 3.45 ng/mL, respectively. The average recoveries of the proposed method in beef samples ranged from 77.3–91.7% with the coefficient of variation less than 12%. The developed FPIA was time-saving that could be completed within 10 min. The FPIA was applied to beef samples and showed a good correlation with liquid chromatography-tandem mass spectrometry (LC-MS/MS) (R2 = 0.9894). Thus, the proposed method provides a rapid, reliable, sensitive, and high-throughput screening tool for the simultaneous screening of eight GCs in beef, which shows great potential in the food safety analysis.

Design, Synthesis, and Characterization of Tracers and Development of a Fluorescence Polarization Immunoassay for Rapid Screening of 4,4'-Dinitrocarbanilide in Chicken Muscle.

The compound, 4,4′-dinitrocarbanilide (DNC), is the marker residue of concern in edible tissues of broilers fed with diets containing anticoccidial nicarbazin (NIC). In this study, 25 fluorescein-labeled DNC derivatives (tracers) are synthesized and characterized to develop a rapid fluorescence polarization immunoassay (FPIA) for the detection of DNC in chickens using DNC monoclonal antibodies (mAbs). The effect of the tracer structure on the sensitivity of the FPIA is investigated. Our results show that after optimization, the half maximal inhibitory concentrations (IC50) and limit of detection (LOD) of the FPIA in the buffer are 28.3 and 5.7 ng mL−1, respectively. No significant cross-reactivity (CR < 0.89%) with 15 DNC analogues is observed. The developed FPIA is validated for DNC detection in spiked chicken homogenates, and recoveries ranged from 74.2 to 85.8%, with coefficients of variation <8.6%. Moreover, the total time needed for the detection procedure of the FPIA, including sample pretreatment, is <40 min, which has not been achieved in any other immunoassays for DNC from literature. Our results demonstrate that the FPIA developed here is a simple, sensitive, specific, and reproducible screening method for DNC residues in chickens.

Development of an Ultrasensitive and Rapid Fluorescence Polarization Immunoassay for Ochratoxin A in Rice.

Ochratoxin A (OTA) is a known food contaminant that affects a wide range of food and agricultural products. The presence of this fungal metabolite in foods poses a threat to human health. Therefore, various detection and quantification methods have been developed to determine its presence in foods. Herein, we describe a rapid and ultrasensitive tracer-based fluorescence polarization immunoassay (FPIA) for the detection of OTA in rice samples. Four fluorescent tracers OTA-fluorescein thiocarbamoyl ethylenediamine (EDF), OTA-fluorescein thiocarbamoyl butane diamine (BDF), OTA-amino-methyl fluorescein (AMF), and OTA-fluorescein thiocarbamoyl hexame (HDF) with fluorescence polarization values (δFP = FPbind-FPfree) of 5, 100, 207, and 80 mP, respectively, were synthesized. The tracer with the highest δFP value (OTA-AMF) was selected and further optimized for the development of an ultrasensitive FPIA with a detection range of 0.03–0.78 ng/mL. A mean recovery of 70.0% to 110.0% was obtained from spiked rice samples with a relative standard deviation of equal to or less than 20%. Good correlations (r2 = 0.9966) were observed between OTA levels in contaminated rice samples obtained by the FPIA method and high-performance liquid chromatography (HPLC) as a reference method. The rapidity of the method was confirmed by analyzing ten rice samples that were analyzed within 25 min, on average. The sensitivity, accuracy, and rapidity of the method show that it is suitable for screening and quantification of OTA in food samples without the cumbersome pre-analytical steps required in other mycotoxin detection methods.

Design, synthesis and characterization of tracers and development of a fluorescence polarization immunoassay for the rapid detection of ractopamine in pork

In this study, 10 fluorescein-labeled ractopamine (RAC) derivatives (tracers) were synthesized and characterized to develop a rapid fluorescence polarization immunoassay (FPIA) for the detection of RAC in pork, using previously produced RAC polyclonal antibodies. The effect of the tracer structure on the sensitivity of the FPIA was investigated. The specificity of the FPIA was evaluated with 70 β-agonists and β-blockers. The FPIA showed a limit of detection of 0.56 μg kg−1 for RAC in pork, with recoveries ranging from 74.8% to 86.6% in spiked samples. The total analysis time, including sample pretreatment, was less than 1 h. The FPIA was used to screen 150 commercial pork samples for RAC residues and the results were consistent with those of an enzyme-linked immunosorbent assay (ELISA) and ultra-high-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS). Our results demonstrate that the FPIA developed here is a rapid, accurate, and sensitive screening method for RAC residues in pork.

Sensitive Rapid Fluorescence Polarization Immunoassay for Free Mycophenolic Acid Determination in Human Serum and Plasma.

In this Article, we describe a fluorescence polarization immunoassay (FPIA) using a new label-near-infrared fluorescent dye. The developed FPIA method was optimized for the rapid analysis of free mycophenolic acid (MPA) in plasma of transplanted patients. The approach is based on the fluorescence competitive assay between the target immunosuppressant and a novel emissive near-infrared fluorescent dye-tagged MPA and MPA-AO for the binding sites of the anti-MPA antibody. The fluorescent analogue of MPA exhibits emission at 654 nm upon excitation at 629 nm (λexcmax) and shows a good photochemical stability and a significant emission quantum yield (0.16) in phosphate buffer media. Free mycophenolic acid was isolated from blood or plasma samples using ultrafiltration prior to analysis. The sample was incubated for 20 min with 5 μg/mL of anti-MPA antibody and 1 nM of MPA-AO before the measurements. The developed FPIA displays a limit of detection of 0.8 ng/mL (10% binding inhibition) and a dynamic range of 1.7-39 ng/mL (20%-80% binding inhibition) in a PBST buffer, fitting the therapeutic requirements. The immunoassay selectivity was evaluated by measuring the cross-reactivity to other immunosuppressive drugs administered in combination with MPA (cyclosporin A and tacrolimus), as well as for the metabolite MPA glucuronide. The assay has been successfully applied to the analysis of free MPA in the blood of a heart-transplanted patient after oral administration of both mycophenolate mofetil (MMF) and tacrolimus, and the results have been compared with those obtained by rapid-resolution liquid chromatography with diode array detection (RRLC-DAD).

Determination of Ochratoxin A in Rye and Rye-Based Products by Fluorescence Polarization Immunoassay.

A rapid fluorescence polarization immunoassay (FPIA) was optimized and validated for the determination of ochratoxin A (OTA) in rye and rye crispbread. Samples were extracted with a mixture of acetonitrile/water (60:40, v/v) and purified by SPE-aminopropyl column clean-up before performing the FPIA. Overall mean recoveries were 86 and 95% for spiked rye and rye crispbread with relative standard deviations lower than 6%. Limits of detection (LOD) of the optimized FPIA was 0.6 μg/kg for rye and rye crispbread, respectively. Good correlations (r > 0.977) were observed between OTA contents in contaminated samples obtained by FPIA and high-performance liquid chromatography (HPLC) with immunoaffinity cleanup used as reference method. Furthermore, single laboratory validation and small-scale collaborative trials were carried out for the determination of OTA in rye according to Regulation 519/2014/EU laying down procedures for the validation of screening methods. The precision profile of the method, cut-off level and rate of false suspect results confirm the satisfactory analytical performances of assay as a screening method. These findings show that the optimized FPIA is suitable for high-throughput screening, and permits reliable quantitative determination of OTA in rye and rye crispbread at levels that fall below the EU regulatory limits.

Rapid Fluorescence Polarization Immunoassay for Highly Sensitive Detection of 2,4,6-Trinitrotoluene

Rapid Fluorescence Polarization Immunoassay for Highly Sensitive Detection of 2,4,6-Trinitrotoluene

A rapid fluorescence polarization immunoassay for the determination of T-2 and HT-2 toxins in wheat

A rapid fluorescence polarization (FP) immunoassay has been developed for the simultaneous determination of T-2 and HT-2 toxins in naturally contaminated wheat samples. Syntheses of four fluorescein-labelled T-2 or HT-2 toxin tracers were carried out and their binding response with seven monoclonal antibodies was evaluated. The most sensitive antibody-tracer combination was obtained by using an HT-2-specific antibody and a fluorescein-HT-2 tracer. The developed competitive FP immunoassay in solution showed high cross-reactivity for T-2 toxin (CR% = 100%) while a very low CR% for neosolaniol (0.12%) and no cross-reactivity with other mycotoxins frequently occurring in wheat. A rapid extraction procedure using 90% methanol was applied to wheat samples prior to FP immunoassay. The average recovery from spiked wheat samples (50 to 200 μg kg(-1)) was 96% with relative standard deviation generally lower than 8%. A limit of detection of 8 μg kg(-1) for the combined toxins was determined. Comparative analyses of 45 naturally contaminated and spiked wheat samples by both the FP immunoassay and high-performance liquid chromatography/immunoaffinity clean-up showed a good correlation (r = 0.964). These results, combined with the rapidity (10 min) and simplicity of the assay, show that this method is suitable for high throughput screening as well as for quantitative determination of T-2 and HT-2 toxins in wheat.

Development of a rapid, specific fluorescence polarization immunoassay for the herbicide chlorsulfuron

A strategy for design of a derivative of chlorsulfuron, which mimics half of the herbicide molecule, was proposed. The 1-[(2-chloro)phenylsulfonyl]monoamidosuccinic acid was synthesized as a derivative of chlorsulfuron for conjugation to carrier proteins. Rabbits were immunized and the resulting polyclonal antibodies were assessed by the fluorescence polarization technique. The antibodies were highly specific to chlorsulfuron. Cross-reactivity to the structurally similar sulfonylurea and urea herbicides chlorbromuron, amidosulfuron, chlortoluron, isoproturon, diuron and linuron was less than 0.1%. A rapid fluorescence polarization immunoassay (FPIA) for chlorsulfuron detection in water samples was developed and optimized. The detection limit of chlorsulfuron in 50 μl of sample was 10 ng ml −1. Total time for the measurement of 10 samples is 7 min. The proposed FPIA is suitable for rapid testing for pesticide contamination where the highest sensitivity is not critical or in combination with pre-concentration techniques.

Fluorescence polarization immunoassay of urinary vanillylmandelic acid

This rapid fluorescence polarization immunoassay for urinary vanillylmandelic acid (VMA) involves use of our previously described antiserum and label and the program for 5-hydroxyindoleacetic acid in the Abbott TDx fluorimeter. Urine samples were measured directly, without pretreatment. The minimum detectable concentration was 0.3 mg/L, and the range of the standard curve was 0.3-200.0 mg/L. Precision, analytical recovery, and correlation of results with those by the Pisano method (Clin Chim Acta 1962;7:285-91) were all satisfactory. With this procedure one can determine the VMA concentration in 10 urine sample in 22 min. This is the first report of a clinical immunoassay for VMA and should greatly simplify screening for neural crest tumors.