Adhesive forces between ligand and receptor measured by AFM

Abstract

Since its invention, the atomic force microscope (AFM) has been used to image a wide range of samples, including soft biological materials. Although various imaging modes have been developed in recent years, the images obtained by these techniques are primarily derived from the mechanical interactions between AFM tip and sample. An imaging mode based on the specific recognition of defined functional groups on the sample by receptor molecules attached to the AFM tip may prove to be beneficial, especially in complex specimens such as the cell membrane. A prerequisite towards this goal is the development of AFM tips functionalized with ligand-specific receptors. Here we report the fabrication of tips functionalized with either avidin or antibodies. These functionalized tips were characterized by force scan measurements on ligands cross-linked to agarose beads. The specificity of the observed adhesion between tip and sample was confirmed by specific blocking of the ligands or the receptors.