Gerhard A. Holzapfel
Graz University of Technology, Institute of Biomechanics
Kronesgasse 5-I, 8010 Graz, Austria
holzapfel@tugraz.at   -   www.biomech.tugraz.at

Cross-linked actin networks are important building blocks of the cytoskeleton. In order to gain deeper insight into the interpretation of experimental data on actin networks, adequate models are required. In this presentation we introduce an affine constitutive network model for cross-linked F-actin networks based on nonlinear continuum mechanics, and specialize it in order to reproduce the experimental behavior of in vitro reconstituted model networks. Continuum mechanical models for cross-linked actin networks seek not only to explain the mechanics of the in vitro model systems but also to interpret the results of more complicated experiments in cell mechanics. Many of these models are based on the microstructure of the network and adopt the idea of integrating the single filament response into a network.

The proposed model is based on the elastic properties of single filaments embedded in an isotropic matrix such that the overall properties of the composite are described by a free-energy function. We also include a contribution from compliant linkers in the continuum model which has the effect of softening actin gels. Finally, the model is enhanced by including a viscoelastic contribution. All that is needed for the finite element implementation is the constitutive model for the filaments, the linkers and the matrix, and the associated elasticity tensor in either the Lagrangian or Eulerian formulation. The model facilitates parameter studies of experimental setups such as micropipette aspiration experiments and we present such studies to illustrate the efficacy of this modeling approach.

GA Holzapfel, MJ Unterberger, RW Ogden: An affine continuum mechanical model for cross-linked F-actin networks with compliant linker proteins. Journal of the Mechanical Behavior of Biomedical Materials, in press.