Peroxidase-Labelled Monoclonal Antibodies for use in Enzyme Immunoassay

Abstract

Desirable characteristics of enzyme-antibody conjugates for use in enzyme immunoassay are labelling uniformity, permanent availability and stability. The use of monoclonal antibodies (MCABS) for preparation of enzyme conjugates, in place of poly-clonal antibodies, ensures labelling uniformity and permanent availability. The problem of stability still exists. Monoclonal antibody-horseradish peroxidase (McAB-HREQ) conjugates produced in our laboratory showed variable stability. After extensive testing of McAB-HRPO conjugates it became obvious that sodium borohydride, used as a reducing agent, did not result in the production of stable conjugates without enzyme pretreatment with fluorodinitrobenzene (FDNB). Ascorbic acid or ethanolamine used as the reducing agent, resulted in McAB-HRPO conjugates which were stable for periods of ten months or more when stored filter sterilized at 4°C.