Nanostructure of Human Arteries under Stress with TR-SAXS

The nanostructure of arterial tissues and its change under tensile load are the prerequisite to understand thoroughly their in vivo function and their mechanics. In this project we want to use Small Angle X-ray Scattering with synchrotron radiation to reveal in situ these nanostructural changes for various types of human arteries (aorta, coronary artery, carotid artery) and additionally for their specific layers (intima, media, adventitia). The mechanical strength of an artery is mainly defined by the amount and orientation of collagen fibres in the different layers. Collagen molecules are on average 300 nm long and have a diameter of 1.4 nm. The nanostructure of the molecules is highly ordered and these repeating structures (distances of 67 nm) are accessible for the diffraction measurements with X-rays. Therefore the X-ray measurements give detailed information on the stress appearing on nanometer scale and on the orientation of these diffracting units. The information, together with the simultaneously macroscopically measured stress-strain behaviour, will be used to extend the physical (constitutive) and computational models for arterial walls, which will lead to significant improvement of some of the "engineering concepts" commonly used. A further task of the project is the implementation of these models into a general purpose finite element program to simulate the experimental findings, and to run more complex boundary-value problems. These tools have a direct application for coronary angioplasty in medicine, as they allow a simulation of the intervention beforehand and optimise the parameters for the treatment. At the same time the gained knowledge of the mechanobiological processes is of fundamental importance for the engineering of artificial tissues needed for replacement in medicine, for which the identification of the critical structural and mechanical requirements is a prerequisite. Hence, the success of tissue engineering, which is a huge industry nowadays, is clearly based on the advanced knowledge of the micro- and nano-structure and the biomechanics of native tissue.

The nanostructure of arterial tissues and its change under tensile load are the prerequisite to understand thoroughly their in vivo function and their mechanics. In this project we want to use Small Angle X-ray Scattering with synchrotron radiation to reveal in situ these nanostructural changes for various types of human arteries (aorta, coronary artery, carotid artery) and additionally for their specific layers (intima, media, adventitia). The mechanical strength of an artery is mainly defined by the amount and orientation of collagen fibres in the different layers. Collagen molecules are on average 300 nm long and have a diameter of 1.4 nm. The nanostructure of the molecules is highly ordered and these repeating structures (distances of 67 nm) are accessible for the diffraction measurements with X-rays. Therefore the X-ray measurements give detailed information on the stress appearing on nanometer scale and on the orientation of these diffracting units. The information, together with the simultaneously macroscopically measured stress-strain behaviour, will be used to extend the physical (constitutive) and computational models for arterial walls, which will lead to significant improvement of some of the "engineering concepts" commonly used. A further task of the project is the implementation of these models into a general purpose finite element program to simulate the experimental findings, and to run more complex boundary-value problems. These tools have a direct application for coronary angioplasty in medicine, as they allow a simulation of the intervention beforehand and optimise the parameters for the treatment. At the same time the gained knowledge of the mechanobiological processes is of fundamental importance for the engineering of artificial tissues needed for replacement in medicine, for which the identification of the critical structural and mechanical requirements is a prerequisite. Hence, the success of tissue engineering, which is a huge industry nowadays, is clearly based on the advanced knowledge of the micro- and nano-structure and the biomechanics of native tissue.