Presence of β-Turn Structure in Recombinant Spider Silk Dissolved in Formic Acid Revealed with NMR

Spider dragline silk is a biopolymer with excellent mechanical properties. The development of recombinant spider silk protein (RSP)-based materials with these properties is desirable. Formic acid (FA) is a spinning solvent for regenerated Bombyx mori silk fiber with excellent mechanical properties. To use FA as a spinning solvent for RSP with the sequence of major ampullate spider silk protein from Araneus diadematus, we determined the conformation of RSP in FA using solution NMR to determine the role of FA as a spinning solvent. We assigned 1H, 13C, and 15N chemical shifts to 32-residue repetitive sequences, including polyAla and Gly-rich regions of RSP. Chemical shift evaluation revealed that RSP is in mainly random coil conformation with partially type II β-turn structure in the Gly-Pro-Gly-X motifs of the Gly-rich region in FA, which was confirmed by the 15N NOE data. In addition, formylation at the Ser OH groups occurred in FA. Furthermore, we evaluated the conformation of the as-cast film of RSP dissolved in FA using solid-state NMR and found that β-sheet structure was predominantly formed.

Spidroin-Based Biomaterials in Tissue Engineering: General Approaches and Potential Stem Cell Therapies

Spider silks are increasingly gaining interest for potential use as biomaterials in tissue engineering and biomedical applications. Owing to their facile and versatile processability in native and regenerated forms, they can be easily tuned via chemical synthesis or recombinant technologies to address specific issues required for applications. In the past few decades, native spider silk and recombinant silk materials have been explored for a wide range of applications due to their superior strength, toughness, and elasticity as well as biocompatibility, biodegradation, and nonimmunogenicity. Herein, we present an overview of the recent advances in spider silk protein that fabricate biomaterials for tissue engineering and regenerative medicine. Beginning with a brief description of biological and mechanical properties of spidroin-based materials and the cellular regulatory mechanism, this review summarizes various types of spidroin-based biomaterials from genetically engineered spider silks and their prospects for specific biomedical applications (e.g., lung tissue engineering, vascularization, bone and cartilage regeneration, and peripheral nerve repair), and finally, we prospected the development direction and manufacturing technology of building more refined and customized spidroin-based protein scaffolds.