Immunosensor Accuracy Improved by Coating Beads with Poly-2-[3-(Methacryloylamino)Propylammonio]Ethyl 3-Aminopropyl Phosphate

Abstract

Poly-2-[3-(methacryloylamino)propylammonio]ethyl 3-aminopropyl phosphate (poly-3MAm3AP) is a polymer that contains phosphorylcholine groups that can attract water to form a water layer, and amino groups that can be used for the covalent attachment of receptors such as anti-LH (Luteinizing hormone) antibody and LH antigen. Poly-3MAm3AP was synthesized with the anticipation that it would aid the recognition of a large number of analytes and eliminate nonspecific adsorption. Poly-3MAm3AP was coated on beads and served as an antigen-antibody reaction interface. The specificity of this surface was evaluated using surface plasmon resonance (SPR) by comparing responses to specific anti-LH antibody and nonspecific anti-hemoglobin antibody.Poly-3MAm3AP did not adsorb nonspecific antibody due to the presence of free water associated with the phosphorylcholine moiety. An immunosensor system was fabricated by combining poly-3MAm3AP-coated beads containing immobilized anti-LH antibody with an optical detector. Poly-3MAm3AP not only reduced nonspecific adsorption, but also increased the amount of specific antibody-antigen interaction. These favorable characteristics are due to an increased amount of immobilized receptor and an increased amount of space for antigen-antibody interaction arising from electrostatic repulsion within the poly-3MAm3AP electrolyte.