Nanostructure and physical properties of collagen biomaterials : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Manawatu, New Zealand
Collagen is the main structural component of leather, skin, pericardium, and other
tissues. All of these biomaterials have a mechanical function and the physical
properties are partly a result of the structure of the collagen fibrils. The
architecture of the collagen network and how it changes when different chemical
and mechanical processes are applied is not fully understood and forms the
foundation of this thesis. Synchrotron-based small angle X-ray scattering has been
used to quantify aspects of the collagen structure, specifically the orientation index
(OI) and D-spacing of the collagen biomaterials investigated. In leather, the
nanostructural changes of the collagen network and the strength of the material
across a range of different animals, through each stage of the leather-making
process, and when model compounds are added or the fat liquor addition is varied
has been investigated. Both the D-spacing and fibril orientation were found to
change with leather processing. The changes to the thickness of the leather during
processing impacts the fibril OI and, once taken into account, the main difference
in OI is due to the hydration state of the material with dry materials being less
oriented than wet. Model compounds urea, proline, and hydroxyproline were
found to increase D-spacing. It was found that as the fat liquor addition is
increased, the D-spacing increased. Pure lanolin resulted in a similar increase in Dspacing.
The collagen fibril structure and strength of both adult and neonatal
pericardium was also investigated. Significant differences were observed with the
neonatal tissue having a higher modulus of elasticity and being significantly more
aligned than adult pericardium. Neonatal pericardium is advantageously thinner
for heart valve applications. This research proves it has the necessary physical
properties required. By understanding the hierarchical structure of collagen and
its mechanisms for modification when subjected to different chemical and
mechanical processes, we gain valuable insight in understanding the performance
of leather and skin in biological, medical, and industrial contexts. This will lead to
better comprehension of current processes and informs future processing
Thesis contains ACS journal articles published with permission:
Sizeland, K. H., Basil-Jones, M. M., Edmonds, R. L., Cooper, S. M., Kirby, N. (2013). Collagen Orientation and Leather Strength for Selected Mammals. Journal of Agricultural and Food Chemistry, 61, 887-892.
Sizeland, K. H., Edmonds, R. L., Basil-Jones, M. M., Kirby, N., Hawley A., Mudie S. T., & Haverkamp R. G. (2015). Changes to Collagen Structure during Leather Processing. Journal of Agricultural and Food Chemistry, 63(9), 2499-2505.
Wells, H. C., Sizeland, K. H., Edmonds, R. L., Aitkenhead, W., Kappen, P., Glover, C., Johannessen, B. & Haverkamp, R. G. (2014). Stabilizing Chromium from Leather Waste in Biochar. ACS Sustainable Chem Eng, 2(7), 1864-1870.
Wells, H. C., Sizeland, K. H., Kirby, N., Hawley, A., Mudie, S. T., & Haverkamp, R. G. (2015). Collagen Fibril Structure and Strength in Acellular Dermal Matrix Materials of Bovine, Porcine, and Human Origin. ACS Biomat Sci Eng, 1(10), 1026-1038.