Molecular recognition plays a central role in cellular behavior and immunological response in the human body, and is the basis for many bioanalytical techniques. Using atomic force microscopy, we have measured directly the molecular recognition forces between individual ligand-receptor, antibody-antigen, and DNA-DNA molecules with high force and displacement sensitivity. Now, can force also be used to develop novel biosensors with single molecule sensitivity? We have developed three biosensors that can perform these measurements in a single, simple operation. Magnetic microbeads are used to pull on DNA-DNA or antibody-antigen bonds with a known force. The strengths of the bonds are tested by observing whether the beads detach from the surface allowing force to discriminate between specific and nonspecific adsorption. This observation can be made with a micromechanical sensor, magnetoresistive sensor, or optical microscope. We have applied this technology to detect proteins, viruses and bacteria, focusing on potential biological warfare agents.

*CC, MPM, ANS & KAW are employees of Nova Research, Inc.