Dr. L. Benjamin Freund
Adjunct Professor of Materials Science and Engineering, University of Illinois at Urbana-Champaign; H. L. Goddard University Professor Emeritus, Brown University
"Analysis of Cell Adhesion Phenomena as Observed at Different Size Scales"
Abstract: We discuss several phenomena, each concerned with an aspect of adhesion of a cell to its surroundings or to another cell, but which are observed at different size scales. In each case, recently reported laboratory observations provide a framework for quantitative modeling of the underlying phenomenon. At the smallest scale, we consider the separation of specific molecular bonds under the action of externally applied forces (as observed by Evans and co-workers with the bio-membrane force probe, for example) with a view toward characterization of the bond structure and rate sensitivity from separation data. At an intermediate size scale, we consider a physical basis for the maximum spacing between cell/substrate bonding sites common among several cell types (observed by Spatz and co-workers, for example). It is demonstrated that thermal fluctuations alone imply that membrane bonding cannot occur if bond site spacing is beyond some system specific threshold level. Lastly, at the scale of cell interactions within compact clusters of thousands of cells, we consider the forces that come into play as the shape of such a cluster changes spontaneously (as observed by Morgan and co-workers, for example). Recent progress toward development of mathematical models for each of these phenomena is summarized.