Residues of Salbutamol and Identification of Its Metabolites in Beef Cattle

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.

Current perspective on veterinary drug and chemical residues in food of animal origin

The marked increase in the demand for animal protein of high quality necessitates protecting animals from infectious diseases. This requires increasing the use of veterinary therapeutics. The overuse and misuse of veterinary products can cause a risk to human health either as short-term or long-term health problems. However, the biggest problem is the emergence of resistant strains of bacteria or parasites. This is in addition to economic losses due to the discarding of polluted milk or condemnation of affected carcasses. This paper discusses three key points: possible sources of drug and chemical residues, human health problems, and the possible method of control and prevention of veterinary drug residues in animal products.

Excretion and Residual Concentration Correlations of Salbutamol Between Edible Tissues and Living Samples in Pigs and Goats

Illegal use of salbutamol (SAL), a β-adrenergic leanness-enhancing agent, has posed potential threat to human health in China. The excretion and depletion of SAL in pigs and goats were investigated, and the concentration correlations between edible tissues and living samples were analyzed to find out a suitable living sample for pre-slaughter monitoring of SAL in pigs and goats. After a single oral dosage of 1.2 mg/kg SAL, approximately 70% of the dose was excreted by pigs and goats from their excreta. When pigs and goats were supplied feed containing SAL (20 mg/kg) for 14 consecutive days, high concentrations of SAL were observed in the liver and kidneys, and the longest persistence was observed in hair. Unlike pigs, SAL was presented primarily as conjugated SAL in goats. Excellent concentration correlations of SAL were observed between urine and edible tissues both in pigs and goats, and in addition, good correlations also were found between hair and edible tissues in pigs and between feces and edible tissues in goats. Hence, urine and hair could accurately predict SAL concentrations in edible tissues of pigs, whereas feces and urine were satisfactory for predicting SAL concentrations in edible tissues of goats. These data make it possible for pre-slaughter monitoring of SAL residues in the edible tissues of pigs and goats.

Complete antigen-bridged DNA strand displacement amplification immuno-PCR assay for ultrasensitive detection of salbutamol

Monitoring of low-level analytes are typical examples for analytical challenges. Salbutamol (SAL), a phenol-β2-agonist, has a very low residual content in the environment. Here, we present an ultrasensitive complete antigen-bridged PCR assay for detecting salbutamol (SAL). These DNA probes modified SAL complete antigens target recognition SAL antibodies and agglutinate synthetic DNA conjugates, thus enabling ligation of DNA probes to form a full-length DNA amplicon that contained a recognition site for cleavage endonuclease and subsequent quantification by qPCR. Moreover, SAL antibodies were modified with magnetic beads which were used to reduce the background noise and sample matrix effect, and the DNA signals were isothermally amplified by strand displacement amplification technology. Some key parameters which influence assay performance were optimized: the length of the bridge oligonucleotide, the concentration of immunomagnetic beads, SAL probes, and initiation chain, etc. Under the optimum conditions, the signal amplification of proposed Immuno-PCR assay for the detection of SAL was exponential, resulting in high potential sensitivity(~1 fg/mL) and a broad detection dynamic range (> 10⁵ fold). Using this proposed method, we detected SAL in spiked tap water and urine samples with acceptable recoveries ranging from 88.1 to 103.3%. Theoretically, the method developed here has broad applicability and practical utility in immunoassays of a wide variety of analytes.

Selective extraction and detection of β-agonists in swine urine for monitoring illegal use in livestock breeding

The illegal use of β-agonists often endangers animal-derived food safety. In this study, a selective detection method for β-agonists in swine urine was established via the combination of polymeric ionic liquid-molecularly imprinted graphene oxide-miniaturized pipette tip solid-phase extraction and high-performance liquid chromatography. It is worth noting that this method relied mainly on the designed adsorbent, which presented a rich adsorption mechanism, fast mass transfer rate, and high selectivity, and was successfully utilized in the selective extraction of β-agonists from swine urine samples. The proposed method has low LOD (0.20-0.56 ng/mL), high recovery (94.9-107.9%), and high reusability (4 times, 91.9-108.8%), which indicates its high potential as a selective, sensitive, accurate, and nonfatal method for monitoring the illegal use of β-agonists in the livestock breeding stage.

Identification of the major metabolites of (R)-salbutamol in human urine, plasma and feces using ultra high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry

(R)-Salbutamol is a selective β2-adrenoreceptor agonist, which produces a short-acting bronchodilator effect and is widely used for the treatment of respiratory diseases in humans. Drug metabolism and identification of the metabolites play an essential role in the evaluation of the overall efficacy and safety of the drugs in clinical practices. There are few reports on the identification of major metabolites of (R)-salbutamol in humans, and the number of identified metabolites is very limited. In this research, a method of ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was developed for the discovery and identification of (R)-salbutamol and its major metabolites in human biological samples. Totally, twelve metabolites of (R)-salbutamol were found and identified and all the metabolites could be found in urine, one metabolite in plasma and two metabolites in feces. Among all the metabolites, eight metabolites have never been reported before. The results indicated that (R)-salbutamol was mainly metabolized through isomerization, oxidation, reduction, glucuronidation, and sulfation pathways in vivo. The possible metabolic pathways of (R)-salbutamol were subsequently presented in this study, which contribute to a better understanding of the metabolism of (R)-salbutamol in humans.

Development of a highly sensitive time-resolved fluoroimmunoassay for the determination of trace salbutamol in environmental samples

Veterinary drug residues have become a major source of environmental pollutants. To monitor trace salbutamol (SAL) in the environment, a highly sensitive and reliable time-resolved fluoroimmunoassay (TRFIA) was developed. Under the optimum parameters, the half-maximal inhibition concentration (IC₅₀) and the limit of detection (LOD, IC₁₀) were determined to be 0.08 μg/L and 0.66 ng/L with a linear range (IC₂₀ - IC₈₀) of 0.0028-2.25 μg/L for SAL. The IC₅₀ and LOD of the TRFIA improved approximately 5-fold and 31-fold, respectively, when compared with our previously reported ELISA data. When compared to most other conventional methods, the TRFIA also showed an excellent sensitivity and accuracy for the detection of SAL. Recoveries from 83.4 to 111.3% and standard deviations (RSDs) from 3.9 to 14.0% were observed in various environmental SAL-spiked samples, including river water, paddy water, livestock wastewater, vegetable field soil and rice paddy soil. In addition, the developed TRFIA showed largely consistent with analytic results from UPLC-MS/MS (R² = 0.9825, n = 15). These results suggest that the proposed TRFIA can be applied as a sensitive and reliable monitoring method to detect trace SAL in environmental samples.

The use of hair as a long-term indicator of low-dose β2 agonist treatments in cattle: Implications for growth-promoting purposes monitoring

The objective of this study was to assess the feasibility of using hair as a long-term indicator of cocktail (low-dose β₂ agonists) treatments in cattle. Six male Simmental cattle were treated with a mixture of low-dose clenbuterol, ractopamine, and salbutamol at dosages of 5.3, 223.3, and 50.0 μg/kg, respectively. The trial lasted for 112 days and included 28 days of treatment and 84 days of withdrawal. Plasma and urine samples taken during the treatment period contained the highest residues, with maximum concentrations of clenbuterol, ractopamine, and salbutamol in plasma of 1.49 ng/mL (Day 21), 43.78 (Day 14) ng/mL, and 8.07 ng/mL (Day 7), respectively, and in urine of 62.40 ng/mL (Day 28), 3995.77 ng/mL (Day 28), and 503.72 ng/mL (Day 1), respectively. On day 42 of withdrawal, the residues of all three β₂ agonists in plasma were below the limit of quantification (LOQ; 0.3 ng/mL for clenbuterol, and 0.5 ng/mL for ractopamine and salbutamol), and in urine samples were below or near the LOQ (the highest being ractopamine at 1.10 ng/mL). The highest concentrations of clenbuterol, ractopamine, and salbutamol in hair were 88.36, 1351.92, and 100.58 ng/g, respectively, on day 14 of withdrawal; and the residues were long-lasting, with 7.64, 28.55, and 8.77 ng/g, respectively, on day 84 of withdrawal. The results of this study demonstrate that hair could be utilized as a long-term indicator of the use of a combination of low-dose β₂ agonists in cattle, which could have implications for growth-promoting purposes monitoring.

Isobaric Tags for Relative and Absolute Quantification (iTRAQ)-Based Untargeted Quantitative Proteomic Approach To Identify Change of the Plasma Proteins by Salbutamol Abuse in Beef Cattle

Salbutamol, a selective β₂-agonist, endangers the safety of animal products as a result of illegal use in food animals. In this study, an iTRAQ-based untargeted quantitative proteomic approach was applied to screen potential protein biomarkers in plasma of cattle before and after treatment with salbutamol for 21 days. A total of 62 plasma proteins were significantly affected by salbutamol treatment, which can be used as potential biomarkers to screen for the illegal use of salbutamol in beef cattle. Enzyme-linked immunosorbent assay measurements of five selected proteins demonstrated the reliability of iTRAQ-based proteomics in screening of candidate biomarkers among the plasma proteins. The plasma samples collected before and after salbutamol treatment were well-separated by principal component analysis (PCA) using the differentially expressed proteins. These results suggested that an iTRAQ-based untargeted quantitative proteomic strategy combined with PCA pattern recognition methods can discriminate differences in plasma protein profiles collected before and after salbutamol treatment.