Immunoassay of low to moderately abundant anionic proteins utilizing selective immobilization to chitosan-coated plates.

The quantitation of low to moderately abundant serum proteins is a common problem encountered in biochemistry. A physical property of the antigen of interest needs to be exploited in the initial binding step of an immunoassay resulting in capture (purification). We describe a two-stage immunoassay utilizing chromogenic and chemiluminescent substrates which is applied to two serum anionic proteins. In this assay, anionic serum proteins are selectively bound to positively charged chitosan-coated polystyrene plates at pH 6.1, in the presence of detergent. The assay has a detection limit of 0.1 microg/mL and a 1000-fold range.