An atomic force microscope (AFM) has been used todirectly monitor specific interactionsbetween antibodies and antigens employed in an immunoassay system.Results were achieved usingAFM probes functionalized with ferritin, and monitoring the adhesiveforces between the probe and anti-ferritin antibody-coated substrates. Analysis of the forcedistribution data suggests a quantization of theforces, with a period of 49 ± 10 pN. This periodic force may beattributed to single unbinding eventsbetween individual antigen and antibody molecules. These resultsdemonstrate that the AFM could beemployed as an analytical tool to study the interactions between themolecules involved in biosensorsystems. The potential of the technique to provide informationrelating to the manner in which the antibodymolecule binds to its specific antigen is also discussed.
