Plasma-polymerized allylamine film used as a new solid phase in immunoradiometric assay (IRMA): effect of antibody (F(ab')2 fragment) concentration on dose response in two-site IRMA.

Abstract

Allylamine (ALAM) film was plasma-polymerized on a flat glass (referred to as ALAM(GLA): GLA refers to a flat glass plate) for use as a solid phase in two-site immunoradiometric assay (two-site IRMA). Adsorption of F(ab')2 anti-human immunoglobulin G [formula: see text] to ALAM(GLA) was larger than adsorption on a polyvinyl chloride plate (referred to as PVC). Contrary to the expectation that the dose response for human IgG (hIgG) on ALAM (GLA) was better than that on PVC, the dose responses on both solid phases were the same. This phenomenon was independent of molecular size of the antigen (Ag) (hIgG or Fc fragment of hIg G (hIgG-Fc)) and also the reaction with protein A (pA). Because direct measurements of binding with 125I-labeled hIgG (hIgG*) or hIgG-Fc (hIgG-Fc*) showed no difference between ALAM(GLA) and PVC, the phenomenon was not due to the second step in the system of two-site IRMA (an Ag--Ab reaction (Ab refers to antibody)). These results indicated that the phenomenon was due to the first step (the adsorption of [formula: see text] to a solid phase). When the concentration of [formula: see text] immobilized on the solid phases was lowered, a significant increase in the dose response was observed for ALAM(GLA).