Imaging of single antigens, antibodies, and specific immunocomplex formation by scanning force microscopy

The most sensitive analytical techniques available today for detecting immuno assay complexes are radio or enzyme immuno analytical techniques, by which quantities of 10⁷-10⁸ analyte molecules can be detected. With the introduction of scanning force microscopy, a new method for detecting biological processes became available. Here, we examine the feasibility of using scanning force microscopy as a biosensitive tool. We demonstrate that single or multiple rabbit anti-human serum albumin molecules form complexes with preadsorbed single human serum albumin molecules on mica. However, no interaction is observed between human immunoglobulin G molecules and preadsorbed single albumin molecules; only separate antigens and antibodies are observed at random positions on the mica. This shows the ability of scanning force microscopy to act as a biosensor for detection of immunocomplexes, and to act as a very powerful tool to study molecule- surface interactions in general.