Regensburg 2010 – scientific programme
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BP: Fachverband Biologische Physik
BP 37: Biomaterials
BP 37.6: Talk
Friday, March 26, 2010, 11:45–12:00, H43
The Effect of Large Strain Deformations on the Non-linear Material Properties of Collagen — •Stefan Münster1,2, Louise Jawerth2, David Weitz2, and Ben Fabry1 — 1Department of Physics, University Erlangen-Nuremberg, Germany — 2Department of Physics, Harvard University, Cambridge, USA
Collagen is the most abundant protein in vertebrates, and its mechanical properties govern the structure and function of many tissues. When subjected to large strain, collagen shows strain-stiffening behavior typical for biopolymers. Here, we investigate how the strain-stiffening response of collagen changes as the material undergoes repeated large strain oscillations. We shear in vitro reconstituted collagen gels in a plate-plate rheometer by applying sinusoidal strain oscillations, and analyze the non-linear stress-strain relationship. With each cycle, the maximum stress and the linear modulus of the material decrease, and the strain-stiffening response occurs at higher strains. Surprisingly, the shape of each stress-strain response is similar to that observed during the previous cycle, only shifted towards larger strain values. Upon addition of covalent crosslinks by incubating the polymerized collagen gels with 2% glutaraldehyde solution, the stress-strain relationship becomes independent of the loading history. We hypothesize that the microscopic mechanism responsible for the history dependence is intra-fibrillar slip of adjacent collagen monomers, which increases the rest lengths of previously strained fibers. A simple visco-elastic model which takes the fibrillar structure of the gels into account shows remarkable similarity with our experimental data.