Anti-mesotrione single chain antibody fragments derived using either phage display or via hybridoma technology: Selection, characterization and stabilization

Single-chain antibody fragments (scAb), specific for the triketone herbicide mesotrione, have been expressed and purified from the bacterium Escherichia coli. ScAbs were identified following the cloning of variable heavy and light chains from anti-mesotrione monoclonal antibodies (mAbs) and from panning an immunized phage display library. Both the monoclonal and phage derived scAbs were produced from the same immunized mouse spleen. In competition ELISA, the mAb derived scAbs (35 and 36) showed similar specificity for mesotrione compared with the parental mAbs. MAb 35 was the most sensitive with a limit of detection (IC20 value) within EC legislative limits for drinking water at 0.04 mug l(-1). The best phage scAb (H6) had sensitivities approximately 20 x less than scAb 35. In competition ELISA, scAb 35 showed reduced sensitivity to sulcotrione, a structurally related triketone, with IC50 values in the muM range. The introduction of an interdomain disulphide bond into scAb 35 resulted in greater stability in non-physiological environments. Immunoassay may provide a simple, cheap and rapid test for detection of mesotrione in a range of environments including soil and food.