Immunoassay elements having a receptor zone

摘要

A dry immunoassay analytical element, for assaying a ligand is disclosed. The element comprises, in the following order, (a) a layer containing a labeled ligand, (b) a bead spreading layer, c) a cross-linked hydrophilic polymer layer and d) a support; wherein (i) a fixed concentration of an immobilized receptor for the labeled ligand is located in a zone at the interface of layers (b) and (c); and (ii) the receptors are immobilized by being covalently bonded to polymeric beads that are smaller than the beads in layer (c).