Development of an analytical method for the determination of beta2-agonist residues in animal tissues by high-performance liquid chromatography with on-line electrogenerated [Cu(HIO6)2]5- -luminol chemiluminescence detection

A portable automated chip for simultaneous rapid point-of-care testing of multiple β-agonists

Abusive use of β-agonists as feed additives for animals and medication is detrimental to human health and food safety. Conventional assays are restricted to a single type of β-agonists detection and cannot match the multiplexing features to perform automated, high throughput, and rapid quantitative analysis in real samples. In this research, we develop a portable automated chip system (PACS) with highly integrated automated devices in conjunction with portable microfluidic chips to provide simultaneous point-of-care testing of multiple β-agonists in the field, simplifying complex manual methods, shortening assay times, and improving sensitivity. Specifically, silicon film is used as reaction substrates for immobilizing the conjugates of β-agonists to increase the sensitivity of the assay result. Then, the PACS with a chemiluminescence imaging detector is established for automatic high-throughput and sensitive detection of Clenbuterol, Ractopamine, and Salbutamol based on the indirect immunoassay. Newly developed chip with high mixing performance can improve the sensitivity of target determination. Multiplex assays were carried out using the developed system for Clenbuterol, Ractopamine, and Salbutamol with a limit of detection of 54 pg mL-1,59 pg mL-1, and 93 pg mL-1, respectively. Except for sample preparation and coating, the detection in the PACS takes less than 47 min. A satisfactory sample recovery (86.33%-108.12%) was obtained, validating the reliability and practical applicability of this PACS. Meanwhile, the PACS enables sensitive and rapid detection of multiple β-agonists in farms or markets where lacking advanced laboratory facilities.

Raman enhancement effect of different silver nanoparticles on salbutamol

Salbutamol is a β-adrenergic receptor agonist compound which has been abused as an animal growth promoter to improve carcass lean meat percentage. At present, the detection of salbutamol by SERS mostly uses gold colloid as substrate, which is expensive and has a high detection limit. In this report, Raman enhancement signal of salbutamol was compared with concentrated gold and silver colloids. The results show that the concentrated silver colloid prepared by reducing silver nitrate with hydroxylamine hydrochloride had superior performance. Three silver colloids with different particle sizes were synthesized by the same reducing agent and used as substrates for spectra acquisition of salbutamol to explore the enhancement performance of different silver nanoparticles sizes on salbutamol. The results showed that silver nanoparticles with larger particle sizes were more conducive to the adsorption of salbutamol. Finally, under the optimal conditions (Silver colloid A as enhanced substrate, 0.2 mol/L NaOH aqueous solution as aggregating compound), a better linear relationship between the concentration of salbutamol (ranged from 0.2 to 1 mg/L) and SERS intensity. The linear equation between SERS intensity and salbutamol concentration was C = 0.0023∙I-0.079 (mg/L) with a good linearity (R² =0.994) and lower root mean square error (RMSE_c = 0.022 mg/L), where C (mg/L) was the concentration of salbutamol solution and I was the SERS intensity of salbutamol solution. Validation set correlation coefficient was 0.988 and prediction root mean square error was 0.029 mg/L. This method provides a new idea for further reducing the detection limit of salbutamol. This study is helpful to further develop a simple and low-cost SERS detection method of salbutamol based on silver colloid.

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Raman enhancement signal of salbutamol was compared with concentrated gold and silver colloids.

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The effect of silver nanoparticles sizes on the enhancement effect are in particular broached.

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The methods can realize salbutamol at trace concentrations detection.

Simultaneous determination of fourteen β2-agonist enantiomers in food animal muscles by liquid chromatography coupled with tandem mass spectrometry

Illegal drug residues in animal derived foods are closely related to human's life and health. Studies on illegal drug residues and the metabolism, such as β2-agonists in animals have attracted more and more attention. In most cases, β2-agonists are suppliedand used astheracemate. The metabolic process and distribution of the two enantiomers in animal tissues are different. Therefore, it is very necessary to develop a simple and fast method for chiral resolution of these drugs in animal tissues. In this paper, a reliable resolution and determination method was presented using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for fourteen enantiomers of seven β2-agonist racemates, clenbuterol (CLE), salbutamol (SAL), cimaterol (CIM), terbutaline (TER), clorprenaline (CLO), tulobuterol (TUL), penbuterol (PEN) in pork, beef, and lamb muscle samples. The samples were added the internal standard solution (IS) and extracted in the alkaline medium with acetonitrile. The further sample purification was accomplished through MCX solid phase extraction cartridge. Chromatographic chiral separation was carried out on a VancoShell chiral column (100 mm × 4.6 mm, 2.7 μm) with an isocratic mobile phase consisting of methanol and 10 mmol mL-1 ammonium formate aqueous solution (85:15, v/v). Under the optimized conditions, the resolution (R) of CIM was 2.0, CLE and PEN were 1.5, the others were all greater than 1.0. Enantiomeric determination was performed in the positive electrospray ionization mode using multiple reaction monitoring (MRM). The correlation coefficient (r) in the range of 0.2-25.0 μg L-1 was above 0.993. The average recoveries at the three spiking levels ranged from 95.3% to 117.7% with the relative standard deviation (RSD) lower than 15%. The limit of detection (LOD) and the limit of quantification (LOQ) of β2-agonist enantiomers was 0.2 μg kg-1 and 0.5 μg kg-1 respectively. The method was successfully applied in the analysis and evaluation of β2-agonist enantiomers in positive food animal muscle samples, CLE, SAL, TEB and CIM enantiomers were detected. The concentrations of the corresponding enantiomers were in the range of 1.06-17.3 μg kg-1, the lowest enantiomer fraction (EF) value was 0.42, and the highest value was 0.69. The work is expected to provide a method for chiral separation and enantiomeric determination of the further study of pharmacology, toxicity and residue elimination of β2-agonist enantiomers.

Nanozyme amplification mediated on-demand multiplex lateral flow immunoassay with dual-readout and broadened detection range

Development of sensitive, facile and rapid biosensors is important for widespread applications. Nanozymes can be ideal signal donors for constructing dual-readout lateral flow immunoassays (LFIA) because they are an excellent class of optical reporters. Herein, a magnetic prussian blue nanozyme (MPBN) mediated dual-readout on-demand multiplex lateral flow immunoassay (MLFIA) was established by employing ractopamine (RAC) and clenbuterol (CLE) as the model analytes. The MPBN was synthesized through in-suit shell-growing and introduced as a bifunctional signal tag owing to their darker original color and peroxidase-like activity. Based on the catalytic signal created by catalyzing oxidation of chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) and colorimetric signal generated by tag's original color, improved precision and broadened detection range were acquired by implementing a dual-readout strategy. And a two-fold increase in the detection range could fulfill different limit requirements of the same target in various regions. The obtained recoveries from 84.01% to 119.94% indicating the repeatability and reliability of the proposed method. This method provides an attractive platform for the detection of a same target with different detection limits, which possesses a considerable potential in monitoring of other targets.

Sensitive and Matrix-Tolerant Lateral Flow Immunoassay Based on Fluorescent Magnetic Nanobeads for the Detection of Clenbuterol in Swine Urine

The lack of sensitivity and poor matrix tolerance are the main bottlenecks of the lateral flow immunoassay (LFIA). Here, a sensitive and matrix-tolerant method that integrated immunomagnetic separation and fluorescent lateral flow immunoassay (IMS-FLFIA) based on fluorescent magnetic nanobeads was developed to detect the clenbuterol (CLE) residue in swine urine. The limit of detection (LOD) of IMS-FLFIA is 4 times lower than that of traditional colloidal gold LFIA. This method, which exhibits similar LOD and linearity range in both phosphate-buffered saline and urine swine, is highly correlated with liquid chromatography-tandem mass spectrometry for the detection of real swine urine samples. The result indicated that IMS-FLFIA has a universal resistance to the swine urine matrix. The merits of this assay, high sensitivity, matrix tolerance, accuracy, and specificity, ensure a promising future in detection of veterinary drug residues.

Computer-Aided Design of Molecularly Imprinted Polymers for Simultaneous Detection of Clenbuterol and Its Metabolites

Molecular imprinting technology (MIT) offers an effective technique for efficient separation and enrichment of specific analytes from complicated matrices and has been used for illicit veterinary drug detectionin recent years due to its high selectivity, good chemical stability, and simple preparation. The development of in silico-based approaches has enabled the simulation of molecularly imprinted polymers (MIPs) to facilitate the selection of imprinting conditions such as template, functional monomer, and the best suitable solvent. In this work, using density functional theory (DFT), the molecularly imprinted polymers of clenbuterol and its metabolites were designed by computer-aided at B3LYP/6-31 + G (d, p) level. Screening molecular imprinting components such as functional monomers, cross-linkers, and solvents has been achieved in the computational simulation considerations. The simulation results showed that methacrylic acid (MAA) is the best functional monomer; the optimal imprinting ratio for both clenbuterol (CLB) and its dummy template molecule of phenylephrine (PE) to functional monomer is 1:3, while the optimal imprinting ratio for the two dummy template molecules of CLB's metabolites is 1:5. Choosin gethyleneglycol dimethacrylate (EDGMA) as a crosslinker and aprotic solvents could increase the selectivity of the molecularly imprinted system. Atoms in Molecules (AIM) topology analysis was applied to investigate the template-monomer complexes bonding situation and helped to explain the nature of the reaction in the imprinting process. These theoretical predictions were also verified by the experimental results and found to be in good agreement with the computational results. The computer-simulated imprinting process compensates for the lack of clarity in the mechanism of the molecular imprinting process, and provides an important reference and direction for developing better recognition pattern towards CLB and its metabolite analytes in swine urine samples at the same time.

An improved clenbuterol detection by immunochromatographic assay with bacteria@Au composite as signal amplifier

Immunochromatographic assays (ICAs) are most frequently used for on-site rapid screening of clenbuterol. To improve sensitivity, a novel probe with bacteria as signal carriers was developed. Bacteria can load a great deal of gold nanoparticles (AuNPs) on their surface, meaning much fewer antibodies are needed to produce clearly visible results, although low concentrations of antibody could also trigger fierce competition between free analyte and the immobilized antigen. Thus, a limited number of antibodies was key to significantly improved sensitivity. Analytical conditions, including bacterial species, coupling method, and concentration, were optimized. The visual detection limit (VDL) for clenbuterol was 0.1 ng/mL, a 20-fold improvement in sensitivity compared with traditional strips. This work has opened up a new route for signal amplification and improved performance of ICAs. Furthermore, inactivated bacteria could also be environment-friendly and robust signal carriers for other biosensors.

Development of a highly sensitive and specific monoclonal antibody based enzyme-linked immunosorbent assay for the detection of a new β-agonist, phenylethanolamine A, in food samples

BACKGROUND

All β-agonists are banned as feed additives for growth promotion in animals due to toxic effects on humans after consuming the β-agonist contaminated meats. Phenylethanolamine A (PA) is a newly emerged β-agonist. Thus there is a need to develop highly sensitive and specific analytical methods for the detection of PA in food samples. In this study, the monoclonal antibody (mAb) against PA was produced by hybridoma technology and used for the development of enzyme-linked immunosorbent assay (ELISA).

RESULTS

The IC₅₀ values and limits of detection (LODs) of the ELISA using homogeneous combination of coating antigen/antibody for PA were 0.16 ng mL^-1 and 0.011 ng mL^-1 , respectively. The cross-reactive (CR) values of the assay with 14 structurally related β-agonists were lower than 0.59%. Swine liver and meat samples were spiked with PA at different content and analysed by ELISA. Acceptable recovery rates of 91.40-105.51% and intra-assay coefficients of variation of 1.56-9.92% (n = 3) were obtained. The ELISA for seven spiked samples was confirmed by LC-MS/MS with a high correlation coefficient of 0.9881.

CONCLUSION

The proposed mAb-based ELISA was highly sensitive and specific for PA and could be used as a quantitative/screening method for PA analysis in food samples. © 2016 Society of Chemical Industry.

Rapid screening of toxic salbutamol, ractopamine, and clenbuterol in pork sample by high-performance liquid chromatography—UV method

A rapid and simple high-performance liquid chromatography–UV method was developed for the separation and quantification of salbutamol, ractopamine, and clenbuterol in pork. A mixture of acetonitrile–formic acid–ammonium acetate was used as the mobile phase to separate three β-agonists on a C18 column with gradient. The effects of the addition of formic acid and ammonium acetate to mobile phases on the separation of β-agonists were investigated. These additives can greatly improve the resolution and sensitivity. Under the optimized chromatographic condition, this separation does not need extra sample preparation. Complete baseline separation of three β-agonists was achieved in < 20 minutes; the linear range is 0.2–50 μg/L with a correlation coefficient R² value of > 0.99. Excellent method reproducibility was found by intra- and interday precisions with a relative standard deviation of < 3%. The detection limit (S/N = 3) was found to be <0.05 μg/L; this method can be used for routine screening of the β-agonist residues in foods of animal origin before being identified by confirmatory methods.

A quantum dot based electrochemiluminescent immunosensor for the detection of pg level phenylethanolamine A using gold nanoparticles as substrates and electron transfer accelerators

This study reports the development of an electrochemiluminescent (ECL) immunosensor for ultrasensitive detection of phenylethanolamine A (PA) based on CdSe quantum dots (QDs) and gold nanoparticles (GNPs). The GNPs/ovalbumin-PA/anti-PA-QD immunosensor was fabricated layer by layer using GNPs as substrates and electron transport accelerators. The use of GNPs greatly enhanced the sensitivity for detecting PA due to the excellent electron transportation ability and the large surface area of GNP carriers allowing several binding events of ovalbumin-PA on each nanosphere. Transmission electron microscopy images (TEM), photoluminescence spectra, ultraviolet-visible absorption spectra and dynamic light scattering (DLS) were used to characterize the QDs and GNPs. The sensor was characterized with electrochemical impedance spectra (EIS), and a strong ECL emission of the modified electrode could be observed during the cathodic process of S2O8(2-) and QDs in air-saturated PBS buffer containing 0.1 M K2S2O8 and 0.1 M KCl (pH 7.4). With a competitive immunoassay format, the ECL signal depended linearly on the logarithm of the phenylethanolamine A concentration within a range of 0.02 ng mL(-1) to 50 ng mL(-1), and the detection limit was 0.0047 ng mL(-1), much lower than those reported in the literature. This ECL immunosensor is rapid, simple and sensitive with acceptable precision, and it will extend the application of QD ECL in immunoassays of β-agonists and open new avenues for the detection of food additive residues in the future.

Development of an ultrasensitive immunochromatographic assay (ICA) strip for the rapid detection of phenylethanolamine A in urine and pork samples

In this study a one-step immunochromatographic assay based on competitive format was developed for the rapid detection of phenylethanolamine A (PEAA) residues in urine and pork samples. A monoclonal antibody against PEAA was produced from BALB/c mice immunized with the PEAA-BSA conjugate. The results of this qualitative test strip were to be interpreted visually. The visual detection limit (VDL) and threshold level of the optimized immunochromatographic assay for PEAA were 0.1 ng/mL and 0.5 ng/mL, respectively. Cross-reactions with other β-agonists were not significant inhibitions to the performance of the test strip assay. The results from the test strip were in a good agreement with those obtained using a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay. The immunochromatographic assay developed here was a useful on-site screening tool that is rapid to use, low in cost, and extremely convenient for the detection of PEAA in urine samples and pork samples.

Ultratrace LC-MS/MS analysis of segmented calf hair for retrospective assessment of time of clenbuterol administration in Agriforensics

In agriforensics, time of administration is often debated when illegal drug residues, such as clenbuterol, are found in frequently traded cattle. In this proof-of-concept work, the feasibility of obtaining retrospective timeline information from segmented calf tail hair analyses has been studied. First, an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) hair analysis method was adapted to accommodate smaller sample sizes and in-house validated. Then, longitudinal 1 cm segments of calf tail hair were analyzed to obtain clenbuterol concentration profiles. The profiles found were in good agreement with calculated, theoretical positions of the clenbuterol residues along the hair. Following assessment of the average growth rate of calf tail hair, time of clenbuterol administration could be retrospectively determined from segmented hair analysis data. The data from the initial animal treatment study (n = 2) suggest that time of treatment can be retrospectively estimated with an error of 3-17 days.

Ultrasensitive and quantitative detection of a new β-agonist phenylethanolamine A by a novel immunochromatographic assay based on surface-enhanced Raman scattering (SERS)

Phenylethanolamine A (PA) is a new kind of β-agonist, which was illegally used as a feed additive for growth promotion in China. In this study, a novel immunochromatographic assay (ICA) based on surface-enhanced Raman scattering (SERS) for the ultrasensitive and quantitative detection of phenylethanolamine A is presented. The principle of this new ICA is similar to that based on colloidal gold particles, but using Au(MBA)@Ag-Ab [e.g., polyclonal antibody of PA labeled Au@Ag core-shell nanoparticles (NPs) sandwiched with a Raman reporter (4-mercaptobenzoic acid, MBA)] as a probe. After ICA procedures, the specific Raman scattering intensity of MBA on the test line was measured for quantitative detection of PA. This assay was completed within 15 min. The IC50 and limit of detection (LOD) values of the ICA for PA detection were 0.06 ng mL(-1) and 0.32 pg mL(-1), respectively, which were 1-3 orders of magnitude lower than those obtained by other immunoassays, indicating the ultrasensitivity of this ICA. There was no cross-reactivity (CR) of the assay with another three β-agonists (ractopamine, clenbuterol, and salbutamol), suggesting high specificity of the SERS-based ICA. A spiking experiment revealed that the recoveries of PA from pig urine samples were in range of 99.9- 101.2% with relative standard deviations (RSDs) of 3.6-5.8%. The results demonstrated that this SERS-based ICA was able to quantitatively detect PA in urine samples with high sensitivity, specificity, precision, and accuracy and might be a powerful method for the analysis of other target analytes in the food area.

Preparation of polyclonal antibodies and development of a direct competitive enzyme-linked immunosorbent assay to detect residues of phenylethanolamine A in urine samples

Phenylethanolamine A (PEAA) is a phenethanolamine member of the family of β-adrenergic agonists (β-agonists) compounds. To determine PEAA residues, we established a rapid direct competitive enzyme-linked immunosorbent assay (ELISA) using a polyclonal antibody produced with the immunogen PEAA-HSA conjugate. The antibody showed high sensitivity, where IC(50) and the limit of detection were 0.3 and 0.02 μg/L, respectively. The specificity of the assay was evaluated by the measurement of cross-reactivity of the antibody with 15 β-agonists compounds. The data demonstrated that the antibody was highly specific for PEAA, with negligible cross-reactivity (CR) with other β-agonists compounds (CR < 0.1%) including ractopamine (CR is 0.3%). Recovery rates ranged from 81% to 110%, indicating relatively good parallelism and accuracy of the assay when applied to real samples. The detection limit in blank urine samples was 0.5 μg/L. The coefficient of variation was below 18% and 20% for intra-assay and inter-assay, respectively, demonstrating an acceptable level of precision. Largely consistent results were obtained for the urine samples by ELISA and UPLC-MS/MS methods. From a practical point of view, the prototype kit could be advantageously used for the screening of large groups of urine samples, and the kit employed has reliability even in routine application for the control of the illegal use of the drug.

Optical biosensors for food quality and safety assurance-a review

Food quality and safety is a scientific discipline describing handling, preparation and storage of food in ways that prevent food borne illness. Food serves as a growth medium for microorganisms that can be pathogenic or cause food spoilage. Therefore, it is imperative to have stringent laws and standards for the preparation, packaging and transportation of food. The conventional methods for detection of food contamination based on culturing, colony counting, chromatography and immunoassay are tedious and time consuming while biosensors have overcome some of these disadvantages. There is growing interest in biosensors due to high specificity, convenience and quick response. Optical biosensors show greater potential for the detection of pathogens, pesticide and drug residues, hygiene monitoring, heavy metals and other toxic substances in the food to check whether it is safe for consumption or not. This review focuses on optical biosensors, the recent developments in the associated instrumentation with emphasis on fiber optic and surface plasmon resonance (SPR) based biosensors for detecting a range of analytes in food samples, the major advantages and challenges associated with optical biosensors. It also briefly covers the different methods employed for the immobilization of bio-molecules used in developing biosensors.

Analytical methods for the detection of clenbuterol

Clenbuterol is therapeutically used for the treatment of pulmonary diseases such as bronchial asthma or for tocolytic reasons. In cattle feeding as well as in sports it is illicitly misused due to its anabolic properties to promote muscle growth. Sample preparation procedures and analytical techniques used for the detection of clenbuterol are manifold and vary with the objectives of the investigation. Methods for its detection in biological specimens, drug preparations, the environment, food and feed products are reported. They are mainly based on immunochemical, chromatographic and mass spectrometric techniques, or on capillary electrophoresis. Sample preparation primarily includes liquid-liquid extraction and solid-phase extraction. Depending on the aim of the method clenbuterol can be determined in single- or multi-analyte methods. In biological and environmental samples concentrations are generally low due to the potency of the drug. Thus, highly sensitive procedures are required for expedient analyses.

Highly sensitive detection of clenbuterol using competitive surface-enhanced Raman scattering immunoassay

In this report, we present a novel approach to detect clenbuterol based on competitive surface-enhanced Raman scattering (SERS) immunoassay. Herein, a SERS nanoprobe that relies on gold nanoparticle (GNP) is labeled by 4,4'-dipyridyl (DP) and clenbuterol antibody, respectively. The detection of clenbuterol is carried out by competitive binding between free clenbuterol and clenbuterol-BSA fastened on the substrate with their antibody labeled on SERS nanoprobes. The present method allows us to detect clenbuterol over a much wider concentration range (0.1-100 pg mL(-1)) with a lower limit of detection (ca. 0.1 pg mL(-1)) than the conventional methods. Furthermore, by the use of this new competitive SERS immunoassay, the clenbuterol-BSA (antigen) is chosen to fasten on the substrate instead of the clenbuterol antibody, which could reduce the cost of the assay. Results demonstrate that the proposed method has the wide potential applications in food safety and agonist control.

Integrated microfluidic immunoassay for the rapid determination of clenbuterol

An integrated microfluidic immunoassay system was established for high throughput analysis of clenbuterol. This system consisted of an integrated microchip and a linear confocal laser induced fluorescence (LIF) scanner. The microchip was composed of three layers: a fluidic channel layer, a PDMS membrane layer and a pneumatic control layer. The multi-layer chip was integrated with 36 pneumatic micro-valves and multiple micro-pumps to realize the flexible reagent delivery, facilitating the automatic assays with less consumption of samples and reduced analysis time. The homemade LIF scanner was able to simultaneously detect multi-channels and provide the potential capability of high throughput assays. The performance of the system was demonstrated by the determination of clenbuterol, one of the most widely used beta-agonists. Under the optimal conditions, the linear range and the limit of detection of clenbuterol were 0 approximately 5.0 ng mL(-1) and 0.088 ng mL(-1), respectively. The recovery rates determined with pig urine samples of 1.0 ng mL(-1) and 2.0 ng mL(-1) were 98.74% and 102.51% (n = 3), respectively. The total detection time was less than 30 min. The system had the potential application for rapid detection of multiple beta-agonists in clinical, pharmaceutical and chemical analyses.