Atomic force microscope imaging contrast based on molecular recognition

Abstract

The contrast in atomic force microscope images arises from forces between the tip and the sample. It was shown recently that specific molecular interaction forces may be measured with the atomic force microscope; consequently, we use such forces to map the distribution of binding partners on samples. Here we demonstrate this concept by imaging a streptavidin pattern with a biotinylated tip in a novel imaging mode called affinity imaging. In this mode topography, adhesion, and sample elasticity are extracted online from local force scans. We show that this technique allows the separation of these values and that the measured binding pattern is based on specific molecular interactions.

Force measurements with the atomic force microscope: Technique, interpretation and applications

“…The ability to resolve specific interactions as antibody-antigen binding between AFM tip and sample surface with nanometer resolution by force distance curves [1188] makes the force volume mode an ideal tool for ''affinity imaging''. It has been applied to biological model systems as biotin-streptavidin [1189], intercellular adhesion molecule-1 (ICAM-1) and anti-ICAM-1 [1159], ferritin-anti-ferritin [1190], fibrinogen-anti-fibrinogen [1191] and tymine and adenine [1192,1193]. The obvious potential for mapping distributions of biomolecules on cell surfaces has been exploited to image distribution of mannan polymers on the yeast cells [1194], sugar chains on tissue sections of the rat vomeronasal epithelium [1195], receptor-associated protein binding proteins on 3T3 fibroblasts [1196], vitronectin receptors on a murine osteoblastic cell [1197], vascular endothelial growth factor (VEGF) receptor on bovine aortic endothelial cells [1198], tyrosine kinase A on PC 12 nerve cells [1199], calcitonin receptors on bone cells [1200].…”

Affinity Imaging of Red Blood Cells Using an Atomic Force Microscope

“…Electrostatic forces (Rotsch and Radmacher 1997), chemical forces (Frisbie et al 1994b), friction forces (Moiseev et al 1991), and elastic (Radmacher et al 1996) properties have been used to image chemical or biological samples. Recently, molecular recognition forces between the biotin-streptavidin pair (Ludwig et al 1997) or antibody-antigen (Hinterdorfer et al 1996) enabled imaging of artificially patterned surfaces. In these experiments, it was possible to discriminate between regions functionalized with streptavidin or with intercellular adhesion molecule-1 (ICAM-1).…”

Microminiaturized Immunoassays Using Atomic Force Microscopy and Compositionally Patterned Antigen Arrays

“…17,18 Similar studies have been conducted on other ligand-receptor systems, 19,20 with several focusing on the streptavidin-biotin system. [21][22][23][24] These determinations are unfortunately affected by nonspecific interactions between a modified probe tip and sample surface, interactions that can have adhesive strengths comparable to those found for the specific interactions between an antigen and its complement antibody. 25 Such determinations require immobilization strategies that result in spatial orientations predisposed to the specific binding interaction between the antigen-antibody pair as a probe tip approaches a sample surface.…”