Application of polymer-protected ultrafine platinum particles to the immunological detection of human serum albumin

The immunological properties of ultrafine platinum particles protected with poly(methyl acrylate)-co-N-vinyl-2-pyrrolidone, having a group chemically reactive with protein, were examined. Polymer-protected ultrafine particles were able to chemically bond multiple human serum albumin (HSA) molecules on their surface. The particles behaved as a multiepitope-type antigen for the immunoreaction. In an ELISA, the HSA-bound particles and HSA molecules competitively reacted against the anti-HSA monoclonal antibodies. The limit of detection of HSA was ca. 10 ng/ml in the assay. The particles were used in an immunodot analysis of anti-HSA polyclonal antibody. Within 30 min of the reaction, 110 μg/ml of HSA was detected. The protein fixed polymer-protected ultrafine particles are a useful new material in immunochemistry.