Investigations of Processing–Induced Structural Changes in Horse Type-I Collagen at Sub and Supramolecular Levels

The aim of this work is to evaluate the effects of different extraction and material processing protocols on the collagen structure and hierarchical organization of equine tendons. Wide and Small Angle X-ray Scattering investigations on raw powders and thin films revealed that not only the extraction and purification treatments, but also the processing conditions may affect the extent of the protein crystalline domain and induce a nanoscale “shield effect.” This is due to the supramolecular fiber organization, which protects the atomic scale structure from the modifications that occur during fabrication protocols. Moreover, X-ray analyses and Fourier Transform Infrared spectroscopy performed on the biomaterial sheds light on the relationship between processing conditions, triple helical content and the organization in atomic and nanoscale domains. It was found that the mechanical homogenization of the slurry in acidic solution is a treatment that ensures a high content of super-organization of collagen into triple helices and a lower crystalline domain in the material. Finally, mechanical tensile tests were carried out, proving that the acidic solution is the condition which most enhances both mechanical stiffness and supramolecular fiber organization of the films.