A concentration dependent study of acoustic plate mode immunosensor response using antigen/antibody systems with different binding ability.

Acoustic plate mode sensors have been used to monitor immunochemical reactions as a function of antigen concentration. In the studies, antibodies were covalently linked to the gold-coated sensing surface via mercaptoethanol, aminosilane, and glutaraldehyde. Two antigen/antibody model systems that differ in their ability to mutually bind one another have been used. For sensor operation at about 150 MHz, a detection limit of approximately 0.5 microg/ml was obtained in both cases. No significant difference between the two systems was found for the value of the binding constants. They amount to about 1.10(8) 1/mole and fall well into the range of binding constants reported for homogeneous immunoassays. A comparison of the sensor response obtained for the two model systems shows that about 70% of the immobilized antibodies are active.