A glass-fiber filtration assay for solution phase hapten-antibody binding: Effect of surface treatment with a polycation

Radioligands bound to murine monoclonal and polyclonal antibodies in solution are rapidly and effectively separated from free ligand by filtration through either untreated or polyethylenimine (PEI)-pretreated glass-fiber filters. Ligand binding to selected anti-morphine monoclonal antibodies, determined by filtration through untreated filters, was significantly greater (1.5–3.0-fold) than the binding activities obtained by gel filtration. However, radioactivity retained by filters that were pretreated with PEI (pH 4) was essentially the same as that obtained using the Sephadex G-25 short-column assay. The pH dependence of the retention on the coated fibers suggests that the mechanism of binding of antibodies to glass is different from that to the PEI-treated surfaces. The quantitative aspects of the assay are reported. The method should prove useful where quantitative, rapid and inexpensive binding radioassays need to be performed.