Mechanical Properties of Spider Silk for Use as a Biomaterial - Molecular Dynamics Investigations

Even though silkworms are the most dominant type of silk fibers used for commercial applications, spider silk has a definitive role in biomedical applications due to its biocompatibility and excellent mechanical properties as biomaterials. In recent years, the recombinant production of silk proteins at a larger scale has found new. Spider silk composites with a combination of a variety of other biomaterials have also been used to improve properties such as biocompatibility, mechanical strength, and controlled degradation. [1] A major constituent of spider silk fibers is spidroin proteins. These are made up of repetitive segments flanked by conserved non-repetitive domains. The fiber proteins consist of a light chain and a heavy chain that is connected via a single disulfide bond. [2] The present paper employed steered molecular dynamics (SMD) as the principal method of investigating the mechanical properties of these nanoscale spider silk protein 3LR2, with a residual count of 134 amino acids. [3]. SMD simulations were performed by pulling on the β-chain of the protein in the x-direction while holding the other fixed. The focus of this paper is to investigate the mechanical properties of the nanoscale spider silk proteins with lengths of about 4.5nm in a folded state, leading to an understanding of their feasibility in bio-printing of a composite spider silk biomaterial with a blend of various other biomaterials such as collagen. An in-depth insight into the fraying and tensile deformation and structural properties of the spider silk proteins are of innovative significance for a multitude of biomedical engineering applications. A calculated Gibbs free energy value of 18.59 kCal/mol via umbrella sampling corresponds with a complete separation of a single chain from a spider silk protein in case of fraying. The force needed for complete separation of the chain from the spider silk protein is analyzed and discussed in this paper. It is found that the protein molecule undergoes a tensile stretch at strain rates of ≅ 11.65. An elastic modulus of 20.136 GPa, calculated via simple SMD simulations by subjecting the silk β-chain to a tensile stretch is also presented.