THE APPLICATION OF FORCE MICROSCOPY TO IMMUNODIAGNOSTIC SYSTEMS - IMAGING AND BIOMOLECULAR ADHESION MEASUREMENTS

Affinity chromatography separation methods, biosensing devices and man y diagnostic materials rely on the immobilization of biomolecules to s olid supports. For example, immunoassays employ antibody molecules imm obilized so that they are able to detect antigen present in the surrou nding analyte. The development of the scanning probe microscopes has p rovided new tools for investigating such sensor surfaces. In the first section of this paper, tapping-mode atomic force microscopy (AFM) is employed to investigate the surface topographies of functionalized imm unoassay substrates. Images of each biomolecular layer in an immunoass ay system are produced with molecular resolution. In the second sectio n of the paper, we investigate the ability of AFM probes coated with f erritin molecules to map the functionality of an anti-ferritin antibod y-coated surface, via biomolecular recognition processes. Novel data a nalysis is utilized to produce two-dimensional maps of probe-sample in teraction, in which each pixel point represents a single force measure ment. The experimental data obtained illustrate the potential of the A FM to be used as a tool for the investigation of both surface topograp hy and the distribution of molecular recognition sites on sensor surfa ces.