Supramolecular Assembly and Mechanical Properties of Dermis

The present work is a part of a wider research project which aims at the in vitro tissues and biohybrid generation. The process of generating biological tissues requires benchmarks in order to define the optimal set of design and performance parameters for the tissue of interest. As a consequence of that, my efforts have been devoted to the study of natural tissue. In particular I have focused my attention to their composition, microstructure and macroscopic properties. The first part of the thesis reviews recent studies concerning the assembly and spatial arrangement of some biological macromolecules of interest, which compose the extracellular matrix. The extracellular matrix is indeed largely responsible for the macroscopic physical properties of connective tissues. Skin has been chosen as model of connective tissue to study. This choice is motivated by the fact that skin is a more general model rather then tendons, which are mainly subjected to uniaxal tension, and the osmosis-supported cartilage. An experimental campaign has been designed in order to gather information on dermal composition and structure, and how these characteristics can affect the macroscopic behaviour of the tissue. The results of this experimental campaign are shown in the second part of the work. At last two constitutive equations are presented. Both of them are developed within the framework of continuum mechanics. The first one is a full three dimensional model able to capture the elastic behaviour of dermis at large deformations. The second model is able to predict the viscoelastic behaviour. Both model accounts for the anisotropy of the native tissue and are structural model, since they contain parameters on the underlying histology. The development of these models provide noteworthy information on the performance of tissue-engineered constructs whose properties have been designed ab initio. In particular, since the mechanical properties of biohybrids can be on-line monitored during culturing in bioreactors. Thus constitutive models can provide cues on the evolution of the mechanical properties, giving the chance to investigate on the complex relationship between mechanical stimulus and tissue remodelling.