Development of an immunochromatographic strip assay for ractopamine detection using an ultrasensitive monoclonal antibody

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.

Affinity-Based Analysis Methods for the Detection of Aminoglycoside Antibiotic Residues in Animal-Derived Foods: A Review

With the increasingly serious problem of aminoglycoside antibiotic residues, it is imperative to develop rapid, sensitive and efficient detection methods. This article reviews the detection methods of aminoglycoside antibiotics in animal-derived foods, including enzyme-linked immunosorbent assay, fluorescent immunoassay, chemical immunoassay, affinity sensing assay, lateral flow immunochromatography and molecular imprinted immunoassay. After evaluating the performance of these methods, the advantages and disadvantages were analyzed and compared. Furthermore, development prospects and research trends were proposed and summarized. This review can serve as a basis for further research and provide helpful references and new insights for the analysis of aminoglycoside residues. Accordingly, the in-depth investigation and analysis will certainly make great contributions to food safety, public hygiene and human health.

Current Advances in Immunoassays for the Detection of β2-Agonists

β2-agonists are a group of synthetic phenylethanolamine compounds which are traditionally used for treating bronchospasm. These compounds can also increase skeletal muscle mass and decrease body fat. The illegal use of β2-agonists in food-producing animals results in residue of β2-agonists in edible tissues and causes adverse health effects in humans. Thus, the detection of β2-agonists at trace level in complex sample matrices is of great importance for monitoring the abuse of β2-agonists. Many methods have been developed to detect β2-agonists. Among them, a variety of antigen–antibody interaction-based techniques have been established to detect β2-agonists in various samples, including animal feed, urine, serum, milk, tissues and hair. In this review, we summarized current achievement in the extraction of β2-agonists from testing samples and detection of β2-agonists using immunological techniques. Future perspectives were briefly discussed.

Hapten synthesis and antibody production for the development of a paper immunosensor for lean meat powder zilpaterol

An anti-zilpaterol mAb with an IC₅₀ of 0.31 ng mL⁻¹ and a limit of detection (LOD) of 0.02 ng mL⁻¹ has been developed. For semi-quantitative detection in pork samples, the visual LOD is 0.5 ng mL⁻¹ and the cut-off value is 5 ng mL⁻¹.

Two-dimensional binary nanosheets (Bi2Te3@g-C3N4): Application toward the electrochemical detection of food toxic chemical

Bismuth telluride is considered as an efficient and super-active electrocatalyst in the sector of electrochemical application. Herein, we prepared binary nanosheets (Bi₂Te₃) through simple solvothermal and hydrothermal method. Furthermore, to enhance the electrocatalytic activity, graphitic carbon nitrides nanosheets (g-C₃N₄) were used to prepare the composition of Bi₂Te₃/g-C₃N₄ binary nanosheets (BNs) with help of hydrothermal energy. Moreover, Bi₂Te₃/g-C₃N₄ hybrid was characterized by various techniques (XRD, XPS, SEM, TEM, EDS and EIS analysis). The electrochemical performance of Bi₂Te₃/g-C₃N₄ BNs modified GCEs were analyzed by electrochemical technique (DPV, EIS and CV methods). As modified the Bi₂Te₃/g-C₃N₄ BNs modified electrode exhibits excellent electrochemical activity towards food toxic ractopamine (RAC) with high-sensitive and nano-molar detection limit (LOD). Besides, the practical ability was analyzed to detect the RAC in meat samples using Bi₂Te₃/g-C₃N₄ BNs modified GCE.

Ultramarine blue nanoparticles as a label for immunochromatographic on-site determination of ractopamine

A competitive immunochromatographic assay (ICA) is presented and used for on-site determination of ractopamine (RAC). Ultramarine blue nanoparticles were directly separated from ultramarine blue industrial products by centrifugation (< 10,000 rpm and > 4000 rpm) and used as visible labels in ICAs. The ultramarine blue nanoparticles were coated by polyacrylic acid (PAA), which provides carboxyl groups on the surface of ultramarine blue nanoparticles. An anti-RAC monoclonal antibody (mAb) was covalently immobilized on the carboxyl-modified ultramarine blue nanoparticle surface via diimide-activated conjugation between the carboxyl groups on the ultramarine blue nanoparticle surface and the amino groups of the antibodies. RAC and BSA-modified RAC competitively bind to the anti-RAC mAb on the ultramarine blue nanoparticles. The blue band in the test line is generated by the accumulation of ultramarine blue nanoparticles and is negatively associated with the RAC content. Under optimal conditions, the visual limit of detection (vLOD) of this ICA for RAC is 2.0 ng mL^-1, 2.0 ng mL^-1, and 1.0 ng mL^-1 in phosphate-buffered saline (PBS), feed samples, and pork samples, respectively. The ultramarine blue nanoparticle-based ICA also shows no cross activity with salbutamol, clorprenaline, clenbuterol, or terbutaline. Graphical abstract Schematic representation of the ultramarine blue nanoparticles immunochromatographic assay for detection of ractopamine (RAC) based on competitive method. The ultramarine blue nanoparticles were screened from commercial ultramarine pigments for the first time and used to detect ractopamine.

Colloidal Gold Immunochromatographic Strip Assay for the Detection of Azaperone in Pork and Pork Liver

In this study, a highly sensitive and specific monoclonal antibody (mAb) against azaperone was produced. The mAb belonged to the IgG2b subtype and its half maximal inhibitory concentration (IC₅₀) was 0.46 ng/mL. The limit of detection value was 0.081 ng/mL and the linear range (IC₂₀-IC₈₀) was 0.165-1.29 ng/mL. Based on this anti-azaperone mAb, a colloidal gold immunochromatographic strip assay method was established for the detection of azaperone in pork and pork liver samples. For pork samples, the cutoff value of the colloidal gold immunochromatographic strip assay was 10 ng/g, and the cutoff value was also 10 ng/g in pig liver samples. This colloidal gold immunochromatographic strip assay is a rapid, simple, and practical method for the detection of azaperone in pork and pork liver samples available in markets.

Sonochemical synthesis of perovskite-type barium titanate nanoparticles decorated on reduced graphene oxide nanosheets as an effective electrode material for the rapid determination of ractopamine in meat samples

A simple and facile ultrasound based sonochemical method to incorporate Perovskite-type barium titanate (BaTiO₃) nanoparticles inside the layered and reduced graphene oxide sheets (rGOs) is reported. BaTiO₃@rGOs nanocomposite was characterized by FESEM, HRTEM, EDX, mapping, XRD, XPS and EIS. The results show that the decoration and also incorporation of BaTiO₃ nanoparticles in the multi-layered and ultrasound reduced graphene oxide matrix. Non-enzymatic and differential pulse voltammetric sensor of ractopamine (food toxic) based on the BaTiO₃@rGOs nanocomposite modified screen printed carbon electrode is developed. Compared with the original BaTiO₃/SPCE and rGOs/SPCE, the BaTiO₃@rGOs/SPCE displays excellent current response towards ractopamine and gives linearity in the range of 0.01-527.19 µM ractopamine in neutral phosphate buffer (pH 7.0). The BaTiO₃@rGOs nanocomposite modified sensor also exhibits valuable ability of anti-interference to electroactive analytes. Furthermore, the as-prepared BaTiO₃ NPs@rGOs/SPCE has been applied to the determination of ractopamine in pork and chicken samples.

Novel ractopamine-protein carrier conjugation and its application to the lateral flow strip test for ractopamine detection in animal feed

In this work, a novel conjugate of ractopamine and bovine serum albumin (RAC-BSA) has been developed via the Mannich reaction, with a mole coupling ratio for RAC-BSA of 9:1. The proposed conjugation method provides a simple and one-step method with the use of fewer reagents compared with other conjugation methods for competitive immunoassays. RAC-BSA conjugation was used to fabricate a competitive lateral flow strip test for RAC detection in animal feed. For sample preparation, RAC was spiked in swine feed purchased from the local markets in Thailand, and methanol and running buffer at a volume ratio of 10:90 was used as extraction buffer. The procedures for sample preparation were completed within 25 min. Under optimal conditions, the limit of detection (LOD), assessed by the naked eye within 5 min, was found to be 1 ng/g. A semi-quantitative analysis was also conducted using a smart phone and computer software, with a linearity of 0.075-0.750 ng/g, calculated LOD of 0.10 ng/g, calculated limit of quantitation of 0.33 ng/g, and good correlation of 0.992. The recoveries were found in the range of 96.4%-103.7% with a relative standard deviation of 2.5%-3.6% for intra- and inter-assays. Comparison of the results obtained by the strip test with those obtained by enzyme-linked immunosorbent assay had a good agreement in terms of accuracy. Furthermore, this strip test exhibited highly specific RAC detection without cross reactivity with related compounds. Therefore, the RAC-BSA conjugation via the Mannich reaction can be accepted as a one-step and easy conjugation method and applied to the competitive lateral flow strip test.

Development of Indirect Competitive Enzyme-Linked Immunosorbent and Immunochromatographic Strip Assays for Tiamulin Detection in Chicken

Tiamulin (TML) is a diterpenoid antibiotic used in animals. In this study, a gold nanoparticle immunochromatographic strip assay and an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) were developed to detect the residue of TML in chicken. TML aminobutyric was synthesized and conjugated to keyhole limpet hemocyanin by mixed anhydride method as immunogen, whereas TML was connected to ovalbumin with 1,1'-carbonyldiimidazole as coating antigen. Under optimized conditions, the ultrasensitive monoclonal antibody-based ic-ELISA exhibited a half-maximal inhibitory concentration (IC₅₀) value of 0.36 ng/mL with a working range of 0.14-0.9 ng/mL for TML. A rapid and sensitive immunochromatographic strip assay was developed with a TML cutoff value of 2.5 ng/mL. On the basis of these results, both developed methods are useful for TML detection in chicken.