Direct Measurements of the Cohesive Behavior of Soft Biological Interfaces

摘要

The mechanical strength, reliability and toughness of biological tissues rely on high-performance bio-adhesives composed of proteins and/or polysaccharides. Without these "natural glues", materials such as bone, teeth, seashells or eggshells would simply disintegrate. Therefore, the structure and composition of these bio-glues dictates the strength, toughness, reliability and performance of tissues at a fundamental level. Single-molecule pullout experiments using atomic force microscopes have revealed the extraordinary properties of some proteins involved in adhesion. However, how this nanoscale performance relates to macroscopic interfacial fracture toughness is currently unknown. In this work we present a new interfacial fracture experimental approach based on the standard double-cantilever beam (DCB) test for adhesives used in engineering, which was adapted to take into account the high compliance of the interface compared to the beams. Interestingly, this "rigid" DCB approach leads to the full cohesive law of the interface, which when compared to a single toughness value yields more information on the chemical, molecular and structural mechanisms operating at the interface. As an example we present a study on fibrin, a protein involved in blood clotting and used as a bio-adhesive in surgical procedures. The effects of the substrate and calcium content on adhesion are examined and discussed.