ABSTRACT
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.
ABSTRACT
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.
Subject(s)
Animals , Animal Feed/analysis , Cross Reactions , Enzyme-Linked Immunosorbent Assay/methods , Limit of Detection , Phenethylamines/chemistry , Reagent Strips , Serum Albumin, Bovine/chemistry , SwineABSTRACT
OBJECTIVE: To establish a high sensitivity method for rapid quantitative detection of morphine in the biological samples including serum, saliva and urine. METHODS: With the immunochromatographic lateral flow strip as reaction method, the luminescent lanthanide europium nanoparticles covalently conjugated with morphine monoclonal antibody were adopted as reporters. The morphine antigen and goat anti-mouse antibody were coated at the nitrocellulose membrane separately as the test line and control line. The strip based on competitive inhibition immunoassay principle was detected by the fluorescent reader for rapid quantitative detection of morphine in the biological samples. RESULTS: After experiment optimization, the improved strip could provide the line range 3-3 000 ng·mL-1; precise quality morphine control materials verified CV<10%. There were no cross reactions with amphetamine, methylamphetamine, ketamine and so on; keep the strips at 37 ℃ for 7 d, the performance of the strips did not decline markedly. CONCLUSION: The preliminary established method shows high linearity, precision, specificity and stability. The method could quantitatively detect the morphine in the biological samples in short time. It is supposed to be applied into the grassroots unit.
ABSTRACT
CdSe/ZnSquantumdots(QDs)werepreparedandcovalentlylinkedtoanti-katacalcinmonoclonal antibodies. After modification, the QDs' maximum emission wavelength was shifted to 625 nm from 620 nm while maintaining the spectral properties. Then the QDs labeled lateral flow strip and corresponding fluorescence measuring instrument were designed and fabricated. To reduce the cost of strip by reducing the amounts of monoclonal antibodies, appropriate amounts of QDs labeled monoclonal antibodies were sprayed on the conjugation pad, with just one test line on the strip but without the control line. Parameters of the strip were optimized by measuring the signal to noise ratio. By using the strip and fluorescence measuring instrument, procalcitonin (PCT) could be detected in 20 min, and the quantitative detection range was 0. 2-100 μg/L with sensitivity of 0. 1 μg/L. A total of 22 blood samples were measured by both our method and the commercial instrument used in the hoptital. The results were consistent for their Pearson correlation coefficient (0. 9995) and Kolmogorov-Smirnov test (Sig=1. 0). The rapid quantitative detection method for PCT is of great importance to quantitative detection of bacterial infection and rational usage of antibiotics clinically.