Colloidal gold labeling of monoclonal antibodies for billfish species identification

This study established a lateral flow competitive immunoassay with a colloidal gold-monoclonal antibody probe for the qualitative detection of sailfish serum albumin. The test involves mixing a tissue homogenate with a colloidal gold-monoclonal antibody suspension and applying the mixture to a strip of plastic-backed nitrocellulose membrane. The presence of albumin in a target sample competed with adsorbed antigen and prevented the appearance of a pink color on the nitrocellulose membrane. A non-target sample yielded a pink color when gold-labeled monoclonal antibodies bound to sailfish albumin previously absorbed to the nitrocellulose. Three gold particle sizes for antibody conjugation were evaluated and of these, 41 nm was optimal. The optimal pH for conjugation of anti-sailfish antibody to colloidal gold was 7.0. The assay requires only five minutes to perform and utilizes two solutions.