Collagen is the most abundant protein in the human body. Of the 25 types of collagen known, fibril-forming collagen is the main component in many tissues such as tendons, cartilage and bone to provide the structural framework and the strength of tissues. Fibril-forming collagen is characterized by a hierarchical assembly of substructures. In this hierarchical arrangement, collagen molecules consisting of three polypeptide chains assemble into fibrils with diameters in the range of 10 - 500 nm and the fibrils further assemble into fibers. Due to the limitations in performing mechanical testing on the nanometer and micrometer scale, only very recently studies have been initiated on the mechanical properties of sub-structures like collagen fibrils and the respective influence of each level of the hierarchical structure on the overall mechanical properties of tissue. Next to collagen, many tissues for instance blood vessels contain elastic fibers which are mainly responsible for providing elasticity to tissues and organs in vertebrates. The elastic fibers contain elastin and fibrillin-microfibrils. The role of fibrillin-microfibrils in the mechanical properties of elastic fibers has been a debate for years. It was the aim of this work to explore the relationship between the mechanical properties and structure of collagen fibrils and elastic fibers, which also provides a better insight in the micromechanical behavior of tissues. To achieve this aim, the mechanical properties of single collagen fibrils and elastic fibers were determined using newly developed AFM-based micro-mechanical bending tests and micro-tensile tests. Tensile properties, shear related properties and viscoelastic behavior of single collagen fibrils at ambient conditions and immersed in buffer were determined. Furthermore, the influence of different cross-linking agents on the mechanical properties of collagen fibrils was studied. The mechanical properties of these cross-linked collagen fibrils provided insight into the existence of microfibrils, an intermediate structure between collagen molecules and fibrils. In a separate set of experiments, the mechanical properties of elastic fibers devoid of or containing fibrillin-microfibrils were determined to evaluate the role of fibrillin-microfibrils in the mechanical properties of elastic fibers.
|Qualification||Doctor of Philosophy|
|Award date||15 Feb 2008|
|Place of Publication||Enschede|
|Publication status||Published - 15 Feb 2008|