The research objective of this award is to characterize, investigate, and understand the dynamic mechanical properties of ligand-receptor adhesion bonds through non-contact, cell-free experiments, with a special emphasis on "catch" bonds. Catch bonds are non-covalent ligand-receptor bonds whose dissociation lifetime counter-intuitively increases with increasing tensile force applied to the bond. In other words, catch bonds become stronger upon elongation. However, wide variations in the published data on the mechanical properties of catch bonds suggest that current experimental approaches are inadequate. Studies conducted under this award hypothesize that compressive force and nonlinearity in stiffness play a role in bond properties, particularly during bond rupture. This hypothesis will be tested by experimental investigations of (i) the effects of external forces not only in tension, but also in compression, on ligand-receptor bonds; (ii) the dynamic adhesion and mechanical stiffness properties of these bonds at various time-scales; (iii) and the level of stiffness nonlinearity in these bonds and its relation to bond lifetime. The long-term goal is to understand the ligand-receptor adhesion mechanisms required for the development of higher-order models.
If successful, these studies will add significantly to the field?s understanding of the mechanical properties of ligand-receptor adhesion bonds, including catch bonds. In addition to their potential to increase our fundamental understanding, precise characterization of ligand-receptor bonds may also lead to innovative technologies such as targeted drug delivery, cancer diagnostics, methods for cell sorting, improved tools for computational simulations, and novel classes of sensors and detectors. The project will be conducted by a multi-disciplinary team including faculty from Mechanical Engineering, Chemical and Biomolecular Engineering, and Biology. The educational plan includes course development in the disciplines of the respective Principal Investigators (PIs), participation in the Research Experience for Teachers (RET) program, and incorporation of their results into an ongoing NSF Nanotechnology Undergraduate Education (NUE) project.