An enzyme-linked immunoassay for the detection of medroxyprogesterone acetate in intestines based on monoclonal antibody

A competitive indirect enzyme-linked immunoassay (ciELISA) based on a monoclonal antibody was developed to detect medroxyprogesterone acetate (MPA) in sheep intestines, which are used as sausage casings. MPA has a relative molecular mass of only 344.5, and it has no immunogenicity. By activating MPA with o-carboxymethyl hydroxylamine hemi HCl, a hapten of MPA (3-CMO-MPA) was synthesised and linked to bovine serum albumin (BSA) and ovalbumin (OVA) to prepare artificial antigens. The monoclonal antibody was prepared from mice immunised with MPA-BSA. The ELISA method allowed MPA detection in a range of 0.1-24.3 ng/ml with an average IC50 value of 1.7 ng/ml. The recoveries of MPA from spiked intestinal tissues at levels of 0.5-5 ng/g ranged from 85.2% to 115.1% with CVs of 8.8-11.2%, and the detection limits were 0.5 ng/g in intestinal tissues. The ciELISA test proved to be a rapid, sensitive, economical and reliable method for screening MPA residues in intestinal tissues.