In order to understand the functioning of biological systems, knowledge about the character of specific biomolecular interactions is crucial. This application note will demonstrate the use of atomic force microscopy (AFM) as a biosensor to detect specific interactions between antigens and antibodies. AFM may be employed in ultra-sensitive immunoassay detection without any kind of labe領(lǐng) for both qualitative and quantitative work. Antibody/antigen interactions have been observed by AFM using thick antibody coatings on microtiter wells2; also, antibodies were bound to Langmuir-Blodgett films containing a minor hapten antigen component. DI Multimode V