ADHESIVE FORCES BETWEEN LIGAND AND RECEPTOR MEASURED BY AFM

Since its invention, the atomic force microscope (AFM) has been used t o image a wide range of samples, including soft biological materials. Although various imaging modes have been developed in recent years, th e images obtained by these techniques are primarily derived from the m echanical interactions between AFM tip and sample. An imaging mode bas ed on the specific recognition of defined functional groups on the sam ple by receptor molecules attached to the AFM tip may prove to be bene ficial, especially in complex specimens such as the cell membrane. A p rerequisite towards this goal is the development of AFM tips functiona lized with ligand-specific receptors. Here we report the fabrication o f tips functionalized with either avidin or antibodies. These function alized tips were characterized by force scan measurements on ligands c ross-linked to agarose beads. The specificity of the observed adhesion between tip and sample was confirmed by specific blocking of the liga nds or the receptors.