Development of a broad-spectrum monoclonal antibody-based indirect competitive enzyme-linked immunosorbent assay for the multi-residue detection of avermectins in edible animal tissues and milk.

Avermectins (AVMs) are a group of anti-parasitic agents that have been widely used in food-producing animals. To monitor the residue of the AVMs, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was developed with a simple sample preparation procedure. Conjugates of 4″-HS-IVM/AVM on three different proteins were used to raise a broad-spectrum monoclonal antibody (mAb), 6D4, that had IC50 values for avermectin, ivermectin, eprinomectin and emamectin of 7.2, 10.4, 19.8 and 20.8 µg L-1, respectively. The limit of detection and limit of quantitation of this method for AVMs in various matrix samples ranged from 0.5 to 5.4 µg L-1 and 1.0 to 10.3 µg L-1, respectively. The recoveries of the samples spiked with AVMs were in the range of 78.1-110.5% with coefficients of variation below 14%. The ic-ELISA was applied to monitor ivermectin in the milk samples, and the results showed a good correlation with that of HPLC-MS/MS.

Magnetic solid-phase extraction based on carbon nanotubes for the determination of polyether antibiotic and s-triazine drug residues in animal food with LC-MS/MS.

Carbon nanotubes-magnetic nanoparticles, comprising ferroferric oxide nanoparticles and carbon nanotubes, were prepared through a simple one-step synthesis method and subsequently applied to magnetic solid-phase extraction for the determination of polyether antibiotic and s-triazine drug residues in animal food coupled with liquid chromatography with tandem mass spectrometry. The nanocomposites were characterized by transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometry. The components within the nanocomposites endowed the material with high extraction performance and manipulative convenience. Compared with carbon nanotubes, the as-prepared carbon nanotubes-magnetic nanoparticles showed better extraction and separation efficiencies for polyether antibiotics and s-triazine drugs thanks to the contribution of the iron-containing magnetic nanoparticles. Various experimental parameters affecting the extraction efficiency had been investigated in detail. Under the optimal conditions, the good linearity ranging from 1 to 200 µg/kg for diclazuril, toltrazuril, toltrazuril sulfone, lasalocid, monensin, salinomycin, narasin, nanchangmycin, and maduramicin, low limits of detection ranging from 1 to 5 µg/kg, and satisfactory spiked recoveries (77.1-91.2%, with the inter relative standard deviation values from 4.0 to 12.2%) were shown. It was confirmed that this novel method was an efficient pretreatment and enrichment procedure and could be successfully applied for extraction and determination of polyether and s-triazine drug residues in complex matrices.

[Effects of boron on serum biochemical indexes and microstructure of immune organs in male obese rats].

OBJECTIVE: Effects of boron( B) on the serum biochemical index and microstructure of immune organs in male obese rats were studied. METHODS: 40 male SD rats( 3-month old) were divided into five groups: normal control group, high-fat-diet control group and boron supplemental group of low, medium and high dose, randomly. The normal control group were fed with normal diet, the other 4 groups were fed with highfat diet to establish the model of obesity for 8 weeks. The boron supplemental group of low, medium and high dose were supplemented 20, 40 and 80 mg B / L in drinking water for 90 d, respectively. At the end, the rats were anesthetized and bled. The blood were collected from right atrium to detected the biochemical indexes related to liver function, and the thymus and spleen were obtained to weighted and fixed, then the samples were made into paraffin sections, stained with hematoxylin-eosin( HE) stain, observed and measured the histological parameters of immune organs. RESULTS: Compared with normal control group, the Lee's index and abdominal fat rate, the level of serum low density lipoprotein cholesterol( LDL-c) and the thymus weight were significantly increased( P <0. 05), but the level of serum total protein( TP) and high density lipoprotein cholesterol( HDL-c) were significantly decreased( P < 0. 05) in high-fat-diet control group, 40 mg /L and 80 mg / L supplement groups of boron. However, these detection indexes did not change significantly( P > 0. 05) in 20 mg / L supplement groups of boron. Compared with the high-fat-diet control group, the Lee's index and abdominal fat rate, the level of serum Apolipoprotein B( apo B) and LDL-c, the thymus weight and index were significantly decreased( P < 0. 05), but the level of serum TP and high density lipoprotein cholesterol( HDL-c) were significantly increased( P < 0. 05) in 20 mg /L supplement groups of boron. The level of serum LDL-c and thymus weight was significantly lower( P < 0. 05) in40 mg / L supplement groups of boron. But all the above detection indicators did not change significantly( P > 0. 05) in 80 mg / L supplement groups of boron. Under the microscope, compared with high-fat-diet control group, splenic nodule area was increased significantly( P < 0. 05), splenic periarterial lymphatic sheath, marginal zone and splenic cord were also thicker significantly( P < 0. 05), thymus medulla / cortex ratio decreased significantly( P < 0. 05), the cells arranged closely, vacuolar like structures were less in the thymus medulla of 20 mg / L and 40 mg / L supplement groups of boron. Microstructure of spleen and thymus did not change significantly in 80 mg / L supplement groups of boron. CONCLUSION: Supplementation of 20 mg B / L could decrease the level of serum apo B and LDL-c, and increase the level of serum HDL-c, and protect the liver function and immune organ of rat from damage caused obese by high fat diet.