Development Of A One Step Strip Test For The Detection Of Sulfadimidine Residues In Swine Urine

In this study, hybridoma 3G₇-E8 producing anti-sulfadimidine(SM₂) monoclonal antibody (Mcab) was used to inoculate into Balb/c mice abdominal cavity. The ascites of the mice was collected and puried to obtain the monoclonal antibody. The Mcab was determined with coating antigen C and the results showed that the concentration of the Mcab was 8 mg/ml, the titer of the Mcab was 1:2.1×10⁶ and the 50% inhibition concentration (IC50) was 1.62ng/ml. The cross-reactive rates of the Mcab to SM₂, SDM, SM₁, SMM, SQX, SMZ, SD were 100%, 23%, 12%, 1.6%, 2.1%, 0.1% and 0.9%, respectively.The one step strip test described in this study was developed by means of a competitive immunoassay in which the detector reagent consisted of colloidal gold particles coated with purified monoclonal anti-SM₂ antibodies. The capture reagent in the assay was a SM₂-OVA conjugate which was immobilised on the lateral flow membrane of the strip. The limit of detection of the strip was 5ng/ml for detecting the SM₂ dissolved in water and the limit of detection was 50ng/ml for detecting the SM₂ added in swine urine. Cross-reaction assay showed that the detection results of the strips were all positive when the concentration of SM₂, SM₁ and SDM were higher than 50ng/ml, which suggested that the strip could be used for detection of the total residues of SM₂, SM₁ and SDM in swine urine.Forty-eight samples of swine urine were detected by ELISA kit and the strips at the same time. The results showed that, among the 48 samples, 32 samples were detected positive by ELISA kit with the positive ratio of 66.7%, and 33 samples were detected positive by the strips with the positive ratio of 68.8%. The positive accordance rate of the both methods was 96.9%.The major advantages of the one step strip test were that results could be obtained within 10 min and that all needed reagents were included in the strip. The strips could be used to detect the Sulfonamides residue in swine urine in spots. The method producing the one step strip for SM₂ could be used for reference in the development of one step strips for the detection of other veterinary drugs.