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.

Lateral-flow assay for rapid quantitative detection of clorprenaline residue in swine urine.

Clorprenaline (CLP), a ß2-adrenergic agonist, was first found in veterinary drugs for cold treatment in China in 2013. It is a potential new lean meat-boosting feed additive because it can promote animal muscular mass growth and decrease fat accumulation. A competitive colloidal gold-based lateral flow immunoassay system with a portable strip reader was successfully developed for rapid quantitative detection of CLP residue in swine urine. The detection system was optimized so that the detection can be completed within 9 min with a limit of detection of 0.15 µg · liter(-1). The assay exhibited good linear range from 3.0 to 20.0 µg · liter(-1), with reliable correlation of 0.9970 and with no obvious cross-reaction with five other ß2-agonist compounds. Twenty spiked swine urine samples were tested by lateral flow immunoassay and liquid chromatography-tandem mass spectrometry to confirm the accuracy of the system. Results show good correlation between the two methods. This method is rapid, sensitive, specific, and convenient. It can be applied in the field for on-site detection of CLP in urine samples.

Screening procedures for clenbuterol residue determination in raw swine livers using lateral-flow assay and enzyme-linked immunosorbent assay.

Clenbuterol, which may cause symptoms of increased heart rate, muscular tremors, headache, nausea, and muscular cramps in patients, has been prohibited for consumption in many countries including the European Union, the United States, and China. A rapid lateral-flow strip assay was developed in our laboratory, and results obtained with this assay were compared with those obtained with a commercial enzyme-linked immunosorbent assay (ELISA) kit for the screening of clenbuterol in raw swine liver. A total of 128 swine livers were acquired from five local markets and prepared for analysis by the lateral-flow strip assay and ELISA. Analysis was completed in 10 min with the lateral-flow strip assay and in 90 min with the ELISA. In parallel with the ELISA, the rapid detection strip produced no false-negative results but had a false-positive rate of 6.3%. Cross-reactivity of the strip was assessed and was negative after tests with clenbuterol analogues such as terbutaline, salbutamol, ractopamine, ritodrine, and fenoterol. These data suggest that a lateral-flow strip assay can be used safely as a screening method as part of a clenbuterol residue surveillance program and should be a valuable tool in the food safety field, especially in developing countries.