Simultaneous determination of clenbuterol, chloramphenicol and diethylstilbestrol in bovine milk by isotope dilution ultraperformance liquid chromatography–tandem mass spectrometry

Schisandrin B, a potential GLP-1R agonist, exerts anti-diabetic effects by stimulating insulin secretion

Diabetes mellitus is a metabolic disease that is characterized by elevated blood sugar. Although glucagon-like peptide-1 receptor agonists (GLP-1RA) lower blood glucose in a glucose-dependent manner, most of them are macromolecule polypeptides. Macromolecular peptides are relatively expensive and inconvenient compared with small molecules. Therefore, this study sought to identify the small molecules binding to GLP-1R via cell membrane chromatography (CMC), confirm their agonistic activity, and further study its beneficial effects in a mouse model of type 2 diabetes mellitus (T2DM) induced by a combination of high-fat diet and streptozotocin. We used CMC, calcium imaging and molecular docking techniques to screen and identify the potential small molecule Schisandrin B (Sch B), which exhibits a strong binding effect to GLP-1R, from the small molecule library of traditional Chinese medicine. Through in-vitro experiments, we found that Sch B stimulated insulin secretion in β-TC-6 cells, while GLP-1R antagonist Exendin9-39, adenylate cyclase inhibitor SQ22536, and protein kinase A (PKA) inhibitor H89 could significantly inhibit the insulin secretion induced by Sch B. In vivo, Sch B significantly improved fasting blood glucose levels, intraperitoneal glucose tolerance test damage, and the status of pancreatic tissue damage, and reduced serum insulin levels, total cholesterol, triglyceride and low density lipoprotein in T2DM mice. These results indicate that Sch B alleviates T2DM by promoting insulin release through the GLP-1R/cAMP/PKA signaling pathway, suggesting that Sch B may be a potential GLP-1RA, which is expected to provide a new therapeutic strategy for the prevention and treatment of T2DM.

Effects of sonochemical approach and induced contraction of core-shell bismuth sulfide/graphitic carbon nitride as an efficient electrode materials for electrocatalytic detection of antibiotic drug in foodstuffs

Ultrasonic-enhanced surface-active bismuth trisulfide based core-shell nanomaterials were developed and used as an efficient modified electrode material to construct a highly sensitive antibiotic sensor. The core-shell Bi₂S₃@GCN electrode material was directly synthesized by in-situ growth of GCN on Bi₂S₃ to form core-shell like nanostar (Ti-horn, 30 kHz, and 70 W/cm²). The electrocatalyst of Bi₂S₃@GCN nanocomposites was efficaciously broadened towards electrochemical applications. As synthesized Bi₂S₃@GCN promoted the catalytic ability and electrons of GCN to transfer to Bi₂S₃. The single-crystalline GCN layers were uniformly grown on the surface of the Bi₂S₃ nanostars. Under the optimal conditions of electrochemical analysis, the CPL sensor exhibited responses directly proportional to concentrations (toxic chemical) over a range of 0.02-374.4 μM, with a nanomolar detection limit of 1.2 nM (signal-to-noise ratio S/N = 3). In addition, the modified sensor has exhibited outstanding selectivity under high concentrations of interfering chemicals and biomolecules. The satisfactory CPL recoveries in milk product illustrated the credible real-time application of the proposed Bi₂S₃@GCN sensors for real samples, indicating promising potential in food safety department and control. Additionally, the proposed electrochemical antibiotic sensor exhibited outstanding performance of anti-interfering ability, high stability and reproducibility.

Preparation of magnetic molecularly imprinted polymers for the rapid detection of diethylstilbestrol in milk samples

BACKGROUND

Diethylstilbestrol (DES) residues are harmful to human health because of their potential carcinogenic properties. Therefore, it is important to develop a fast and efficient pretreatment method to prevent their harmful effects on human health and the environment.

RESULTS

In this paper, two types of magnetic molecularly imprinted polymers (MMIPs) of DES were prepared by bulk polymerization and the sol-gel method, respectively. The synthetic materials were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis. Adsorption capacities of the bulk and sol-gel MMIPs were investigated. A rapid detection method was developed using the two types of MMIPs as sorbents, coupled to high-performance liquid chromatography, for the determination of DES residues in milk samples. Under optimized conditions, the limit of detection (S/N = 3) of both methods for DES was 2.0 μg L^-1 ; and the linear response range to DES was 0.1-500 mg L^-1 . The milk samples were analyzed according to this method with good recoveries of 88.3-97.6 and 90.5-103.5% for the two types of MMIPs, respectively.

CONCLUSIONS

The method described had high sensitivity and high selectivity, and could prove to be a new method for the rapid determination of DES residues in milk samples. © 2019 Society of Chemical Industry.

Simultaneous determination of β-agonists on hexagonal boron nitride nanosheets/multi-walled carbon nanotubes nanocomposite modified glassy carbon electrode

β-Agonists are illegally consumed in various products such as food and animal and effect the nutrition distribution owing to change of body fat. In addition, they result in acute poisoning and several symptoms such as muscular tremors and nervousness. A new electrochemical approach based on two-dimensional hexagonal boron nitride (2D-hBN) nanosheets decorated functionalized multi-walled carbon nanotubes (f-MWCNTs) was presented for simultaneous determination of β-agonists such as phenylethanolamine A (PEA), clenbuterol (CLE), ractopamine (RAC) and salbutamol (SAL) in urine samples. X-ray diffraction (XRD) method, Raman spectroscopy, scanning electron microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used characterizations of nanomaterials. After that, 2D-hBN/f-MWCNTs nanocomposite modified glassy carbon electrode (GCE) was prepared for simultaneous determination of β-agonists. 1.0 × 10^-12-1.0 × 10^-8 M and 1.0 × 10^-13 M were founded as the linearity range and the detection limit (LOD) for PEA, CLE, RAC and SAL. Finally, the prepared electrochemical sensor was used for urine sample analysis in presence of ascorbic acid (AA) and uric acid (UA).

Analysis of Diethylstilbestrol Residues in Chicken Using Surface-Enhanced Raman Spectroscopy (SERS) Coupled with Multivariate Analysis

Estrogen residues, including diethylstilbestrol in chicken, are one of the main food safety concerns all over the world owing to a series of negative effects on the human body. Surface-enhanced Raman spectroscopy (SERS) coupled with multivariate analysis was applied to detect rapidly diethylstilbestrol residues in chicken. The detection conditions, including the sizes of colloidal gold nanoparticles (Au NPs) and the additional amounts of Au NPs, chicken extract containing diethylstilbestrol, and magnesium sulfate solution, as well as the adsorption time, were optimized by a single factor experiment to obtain a better detection effect of diethylstilbestrol residues in chicken. Partial least squares regression (PLSR) was the best quantitative model for the detection of diethylstilbestrol residues in chicken by comparing four chemometric models. Diethylstilbestrol residues in chicken could be predicted by PLSR with the low root mean square error (RMSE = 0.4128 mg/L), and the high determination coefficient (R²= 0.9811) and ratio of prediction to deviation (RPD = 7.2566) for the test set. A novel approach, which has the potential for the analysis of other estrogen residues in meat, was developed to detect rapidly the diethylstilbestrol residues in chicken by using SERS coupled with multivariate analysis.

A voltammetric immunosensor for clenbuterol based on the use of a MoS2-AuPt nanocomposite

An ultrasensitive immunosensor for the direct detection of the illegally used livestock feed clebuterol (CLB) is described. It is based on the use of a glassy carbon electrode modified with an MoS₂-AuPt nanocomposite and on biotin-streptavidin interaction. The use of MoS₂-AuPt accelerates electron transfer, and this leads to a sharp increase in the electrochemical signal for the electrochemical probe hydrogen peroxide. Differential pulse voltammetry was used to record the current signal at a peak potential of -0.18 V (vs SCE). Under optimal conditions, the electrode has a linear response in the 10 pg·mL^-1 to 100 ng·mL^-1 CLB concentration range and a 6.9 pg·mL^-1 detection limit (based on the 3σ criterium). This immunosensor is sensitive, highly specific and acceptably reproducible, and thus represents a valuable tool for the determination of CLB in pork. Graphical abstract Schematic of a voltammetric immunosensor for the determination of clenbuterol (CLB) based on the use of a nanocomposite prepared from molybdenum disulfide and a gold-platinum alloy (MoS₂-AuPt), and making use of the biotin-streptavidin system.

Hollow Au-Ag Nanoparticles Labeled Immunochromatography Strip for Highly Sensitive Detection of Clenbuterol

The probe materials play a significant role in improving the detection efficiency and sensitivity of lateral-flow immunochromatographic test strip (ICTS). Unlike conventional ICTS assay usually uses single-component, solid gold nanoparticles as labeled probes, in our present study, a bimetallic, hollow Au-Ag nanoparticles (NPs) labeled ICTS was successfully developed for the detection of clenbuterol (CLE). The hollow Au-Ag NPs with different Au/Ag mole ratio and tunable size were synthesized by varying the volume ratio of [HAuCl4]:[Ag NPs] via the galvanic replacement reaction. The surface of hollow Ag-Au NPs was functionalized with 11-mercaptoundecanoic acid (MUA) for further covalently bonded with anti-CLE monoclonal antibody. Overall size of the Au-Ag NPs, size of the holes within individual NPs and also Au/Ag mole ratio have been systematically optimized to amplify both the visual inspection signals and the quantitative data. The sensitivity of optimized hollow Au-Ag NPs probes has been achieved even as low as 2 ppb in a short time (within 15 min), which is superior over the detection performance of conventional test strip using Au NPs. The optimized hollow Au-Ag NPs labeled test strip can be used as an ideal candidate for the rapid screening of CLE in food samples.

A novel aptasensor for electrochemical detection of ractopamine, clenbuterol, salbutamol, phenylethanolamine and procaterol

β-agonists are phenylethanolamines with different substituent groups on the aromatic ring and the terminal amino group which have the effect of nutrition redistribution and can accumulate in body tissues causing acute or chronic poisoning when consumed. Therefore, it is very important to establish a fast screening method for the detection of several kinds of β-agonists in food safety control. In this study, the aptamer-agonists (AP-Ago) has screened out by Isothermal Titration Calorimetric method. AP-Ago was a single-strand DNA with 22 base-pairs. The dissociation constant (Kd) to phenylethanolamine (PHL) was 3.34 × 10(-5)mol L(-1). The AP-Ago based electrode was constructed by self-assembling on gold electrode. A label-free electrochemical aptasensor was then developed with AP-Ago-based gold electrode, which was sensitive to phenylethanolamine(PHL), clenbuterol (CLB), ractopamine (RAC), salbutamol (SAL) and procaterol (PRO). The detection limits were 0.04 ng/mL (RAC), 0.35 pg/mL (CLB), 1.0 pg/mL (PHL), 0.53 pg/mL (SAL) and 1.73 pg/mL(PRO), respectively, The detection time was 15 min. The reproductivity of the mentioned aptasensor is good with RSD of 2.09%. Comparing with ELISA and HPLC on β-agonists detection in actual sample, this aptasensor is advantage of fewer steps and fast screen-detection of these five β-agonists or their mixtures. This study suggests that the aptasensor can be developed to a rapid screening means with multi-β-agonists (may be one or more) in sample.

Novel spectrophotometric determination of chloramphenicol and dexamethasone in the presence of non labeled interfering substances using univariate methods and multivariate regression model updating

Smart and novel spectrophotometric and chemometric methods have been developed and validated for the simultaneous determination of a binary mixture of chloramphenicol (CPL) and dexamethasone sodium phosphate (DSP) in presence of interfering substances without prior separation. The first method depends upon derivative subtraction coupled with constant multiplication. The second one is ratio difference method at optimum wavelengths which were selected after applying derivative transformation method via multiplying by a decoding spectrum in order to cancel the contribution of non labeled interfering substances. The third method relies on partial least squares with regression model updating. They are so simple that they do not require any preliminary separation steps. Accuracy, precision and linearity ranges of these methods were determined. Moreover, specificity was assessed by analyzing synthetic mixtures of both drugs. The proposed methods were successfully applied for analysis of both drugs in their pharmaceutical formulation. The obtained results have been statistically compared to that of an official spectrophotometric method to give a conclusion that there is no significant difference between the proposed methods and the official ones with respect to accuracy and precision.

Sample preincubation strategy for sensitive and quantitative detection of clenbuterol in swine urine using a fluorescent microsphere-based immunochromatographic assay

We describe an ultrasensitive and quantitative immunochromatographic assay to determine the amount of clenbuterol (CLB) in swine urine. In this study, fluorescein isothiocyanate polystyrene fluorescent microspheres were used as probes. A sample preincubation strategy was introduced to this immunochromatographic assay. Results showed that the strategy evidently improved the sensitivity and accuracy of lateral flow assay. The method was completed in 20 min, and a half-maximal inhibitory concentration of 0.13 μg liter(-1) was obtained. The limit of detection of the proposed method to determine CLB in swine urine was 0.01 μg liter(-1), which was lower than the limit of detection of immunochromatographic assays without preincubation. Intra- and interday recoveries of spiked swine urine ranged from 85.0 to 107.5%. The relative standard deviation values of the preincubated test strip ranged from 2.7 to 12.5%. Analysis of the CLB in swine urine samples showed that the result obtained from the lateral flow assay is consistent with that obtained from a commercial enzyme-linked immunosorbent assay kit. Our results suggest that the developed fluorescent microsphere-based immunochromatographic assay may be useful as a rapid screening method to detect CLB quantitatively.

Liquid chromatography-mass spectrometry method for the quantitative determination of residues of selected veterinary hormones in powdered ingredients derived from bovine milk

A rugged, quantitative liquid chromatography-tandem mass spectrometry method with modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation for 17 selected veterinary hormones in six different powdered ingredients derived from bovine milk was developed and comprehensively validated. A universal post-extraction spiked matrix-matching approach based on whole milk powder has been successfully implemented. Three validation runs based on four levels of pre-extraction spiked quality control (QC) samples have been conducted. Overall accuracy (86-117%), overall precision (<20% RSD), selectivity, absolute extraction recovery (62-82%), matrix effect (<15% for most compounds), limits of detection (0.1-0.8 μg/kg, except for diethylstilbestrol at 3.8 μg/kg), limits of quantitation (0.2-2.0 μg/kg, except for diethylstilbestrol at 10.0 μg/kg), and extract stability (48 h) have been determined. The method is proposed for the routine analysis of hormones potentially present in powdered ingredients derived from bovine milk.

Graphene oxide-modified electrodes for sensitive determination of diethylstilbestrol

This paper reports an electrochemical sensor fabricated with graphene oxide (GO) modified on a chitosan-coated glassy carbon electrode (GO-CS/GCE) and its application for the detection of diethylstilbestrol (DES). It was observed that the effective electrochemical surface area of the GO modified electrode was nearly 10 times that of the bare GCE. This could be used to explain the results that the oxidation peak current of DES on the GO-CS/GCE was much larger than on the bare GCE. Under optimized conditions, the prepared electrode could be used to electrochemically detect DES according to the oxidation of the DES. Based on the technique of differential pulse voltammetry and the accumulation of DES on GO modified electrodes, the calibration curve for DES determination could be obtained with a linear range of 1.5 × 10(-8)-3.0 × 10(-5) M and an estimated detection limit of 3.0 × 10(-9) M (S/N = 3). The feasibility of the developed electrode for tablet sample analysis was investigated. Our investigation revealed that GO could significantly improve the analytical performance of electrochemical sensors.

An adaptive single-well stochastic resonance algorithm applied to trace analysis of clenbuterol in human urine

Based on the theory of stochastic resonance, an adaptive single-well stochastic resonance (ASSR) coupled with genetic algorithm was developed to enhance the signal-to-noise ratio of weak chromatographic signals. In conventional stochastic resonance algorithm, there are two or more parameters needed to be optimized and the proper parameters values were obtained by a universal searching within a given range. In the developed ASSR, the optimization of system parameter was simplified and automatic implemented. The ASSR was applied to the trace analysis of clenbuterol in human urine and it helped to significantly improve the limit of detection and limit of quantification of clenbuterol. Good linearity, precision and accuracy of the proposed method ensure that it could be an effective tool for trace analysis and the improvement of detective sensibility of current detectors.