Analysis of solid-phase immobilized antibodies by atomic force microscopy

Antibody adsorption to solid surfaces creates a number of constraints that may interfere with epitope recognition and ligand-antibody interaction. By optimizing the conditions of adsorption, one may minimize these constraints. We have studied several factors that affect the antibody adsorption using atomic force microscopy (AFM) as a readout mechanism. AFM provides a highly sensitive, label-free method for detecting and analyzing molecular interactions. In this report, AFM was used to study antibody properties, the efficiency of particle capture and ligand-antibody interaction using anti-bacteriophage fd antibodies in a solid phase assay format. The capture efficiencies of anti-fd preparations adsorbed onto gold surfaces under various conditions including pH and antibody concentration were determined and compared. The relative sensitivities of each antibody for the capture of phage fd as a function of applied phage concentrations was evaluated. The collective data indicates that AFM is effective as an analytical instrument for studying the functionality of surface adsorbed antibodies in particle capture assays. This method of analysis can be extended to rapidly screen and select antibodies or other ligands with a specific set of characteristics. As the number and complexity of chip-based analytical platforms in proteomics increases, rapid selection/screening processes such as that described here will become invaluable.