Changes in Natural Silk Fibres by Hydration, Tensile Loading and Heating as Studied by 1H NMR: Anisotropy in NMR Relaxation Times

Structural Characterization and Hydration Dynamics of Cross-Linked Collagen and Hyaluronic Acid Scaffolds by Nuclear Magnetic Resonance

Understanding a biomaterial's structural and hydration dynamics is essential for its development and applications in tissue regeneration. In this study, collagen-hyaluronic acid (HA) scaffolds were analyzed utilizing Nuclear Magnetic Resonance (NMR) techniques to elucidate how different cross-linking conditions influence the internal architecture and interaction with solvents in these scaffolds. The scaffolds were fabricated using 3D printing and cross-linked with 1,4-butanediol diglycidyl ether (BDDGE), a process known to impact their mechanical properties. We gained insights into the microstructural organization and hydration behavior within the scaffolds when exposed to water and ethanol by employing proton relaxation and diffusion measurements. To better understand the system's performance, static and dynamic experiments were performed. Our results indicate that the degree of cross-linking affects the scaffold's ability to retain water, with higher cross-linking leading to more rigid structures. This also altered the hydration dynamics mainly due to a difference in the diffusion of water within the scaffold. In addition, the anisotropy of the collagen fibers also decreases with the cross-linking. Ethanol, a less polar solvent, provided a contrasting environment that further revealed the structural dependencies on the cross-linking density. The study's findings contribute to a deeper understanding of how the structure and morphology affect the functionality of collagen-HA scaffolds, offering critical information for optimizing their design for specific biomedical applications, such as soft tissue regeneration. Our experiments show how NMR is a valuable tool to provide information on dynamic processes not only in collagen-HA scaffolds but also in many biocompatible polymeric samples. The outcomes of this research provide a foundation for future work aimed at tailoring scaffold properties to enhance their performance in clinical settings, ultimately advancing the field of tissue engineering.

Sustainable Bombyx mori's silk fibroin for biomedical applications as a molecular biotechnology challenge: A review

Silk is a natural engineering material with a unique set of properties. The major constituent of silk is fibroin, a protein widely used in the biomedical field because of its mechanical strength, toughness and elasticity, as well as its biocompatibility and biodegradability. The domestication of silkworms allows large amounts of fibroin to be extracted inexpensively from silk cocoons. However, the industrial extraction process has drawbacks in terms of sustainability and the quality of the final medical product. The heterologous production of fibroin using recombinant DNA technology is a promising approach to address these issues, but the production of such recombinant proteins is challenging and further optimization is required due to the large size and repetitive structure of fibroin's DNA and amino acid sequence. In this review, we describe the structure-function relationship of fibroin, the current extraction process, and some insights into the sustainability of silk production for biomedical applications. We focus on recent advances in molecular biotechnology underpinning the production of recombinant fibroin, working toward a standardized, successful and sustainable process.