The Identification of Collagen Failure in Vascular Tissue

Sammanfattning: Aortic diseases are a common and fatal health issue, regarding various conditions targeting the aorta. The arterial wall consists of two proteins; collagen and elastin (fibers), and they will contribute to the elasticity and strength of the wall. In recent times there has been a growing interest in studying the microstructure of the aortic tissues because it is believed that changes in the amount and/or the construction of the fibers will result in mechanical as well as functional changes that are associated with these heart conditions. Therefore, a better understanding of collagen and its load-carrying properties in vascular tissue is needed for others to be able to develop new designs of cardiovascular medical devices that may help the medical field to find other therapies and treatments for patients with aortic diseases.  This bachelor's degree thesis is based on a literature study, experimental testing, finite element method (FEM) analysis, and a microscopy study. To get a broader understanding of the arterial wall, the collagen, and its mechanical properties a literature study was conducted. The experimental testing was made with tensile testing equipment called CellScales BioTester 5000 uniaxial bio-testings and the test specimen used was porcine aorta from a local abattoir. The data obtained from the testing was put in MATLAB to produce graphs visualizing different data, such as; stresses, strain, forces and stiffness. Then a FEM-simulation was made by Christopher Miller and the data and images obtained from the analysis were used to compare with the results from MATLAB. Furthermore, the ruptured test specimen after the tensile testing was sent to Karolinska Institutionen (KI) for a microscope study. The results from MATLAB were used to receive information regarding the material properties, to calculate the stiffness as well as the strain at the rupture. There were two samples made, sample 7 and sample 10, and the data from the MATLAB graphs were used to determine where the rupture occurred. For sample 7 this occurs when the force is 7.29 [N], elongation is 22.93 x 10^(-3) [m] and stress is 1210 [kPa], for sample 10 the rupture of sample 10 occurred when the force is 6.65 [N], elongation is 17.4 x 10^(-3) [m] and stress is 606 [kPa]. The FEM-simulation showed where the maximum deformation takes place, which was in the middle of our tissues. From the microscope images from KI, the accuracy of the FEM-model could be seen.