Mechano-radiological characterization of collagen hydrogel through tensile testing and microstructural analysis

Collagen is at once a main structural material and collagen hydrogel reflects the mechanical behavior of human tissues. As a structural material, it bears and loads stress, and affects cell behavior depending on mechano-sensitivity. Thus, providing mechanical reliability of the collagen hydrogel presents significant challenge, so it is essential to understand its mechanical property. In addition, radiation effects on biomaterials were less focused than the effects on DNA. Considering mechano-sensitivity of cell behavior, radiological effects on biomaterials should be understood. However, soft collagen hydrogels were only tested for shear, compressive and rheological properties because they show instability caused by gravitational forces and dehydration for existing tensile testing methods. In addition, the network structure of the collagen hydrogel varies under applied stress with showing non-linear stress-strain relationship and mechanism for the non-linearity was not proven yet. To predict hydrogels' mechanical behavior accurately, previously unavailable tensile data is required. In this study, we aim to investigate the mechano-radiological behavior of collagen hydrogels under quasi-static tensile stress and providing its mechanical response. Tensile testing and microstructure analysis demonstrate the mechanism of tensile properties and irradiation effects. After the first regime of mechanical behavior, the unfolding dominated deformation of the collagen network is completed, and the stretching dominated deformation of the network begins. These results illustrate that collagen hydrogels respond to tensile stress in complex manners, either as the network or as the fiber, which shows the non-linear stress-strain relationship. Besides, radiation causes scission and crosslinking on the collage fibers. Furthermore, we propose a new approach to tensile behavior and radiological effects for soft and hydrated materials that can be applied throughout the bioengineering field