Selection of a single chain variable fragment antibody against ivermectin from a phage displayed library

Single chain variable fragment antibodies (scFvs) have considerable potential in immunological detection of pesticides, veterinary and other residues. In this study, a large human synthetic phage displayed library was used to select scFvs against ivermectin (IVM) by subtractive panning. After four rounds of panning, seven monoclonal phage particles capable of binding with the IVM were obtained. One of the identified novel anti-IVM scFv, hsIVM8, was expressed in Escherichia coli HB2151 and purified with Ni metal ion affinity chromatography. Sodium dodecyl sulfate polyacrylamine gel electrophoresis (SDS-PAGE) indicated that the relative molecular mass of hsIVM8 was estimated at 28 kDa. The purified hsIVM8 was used to develop a competitive indirect enzyme-linked immunosorbent assay (ci-ELISA) for IVM. The linear range of detection for standards in this ci-ELISA was approximately 0.1-5 microg/mL and 50% inhibition of control (IC(50)) was 4.11 microg/mL for IVM. These results showed promising applications of hsIVM8 for detecting IVM in agricultural and environmental matrices.