Polyelectrolyte Fiber Assembly of Plant-Derived Spider Silk-like Proteins

Abstract

Spider dragline silk is a proteinaceous material that combines superior toughness and biocompatibility, which makes it a promising biomaterial. The distinct protein structure and the fiber formation process contribute to the superior toughness of dragline silk. Previously, we have produced recombinant spider silk-like proteins in transgenic tobacco that are readily purified from plant extracts. The plant-derived spidroin-like proteins consisted of native major ampullate spidroin 1 or spidroin 2 N- and C-termini flanking 8, 16, or 32 copies of their respective consensus block repeats (mini-spidroins). Here, we present the generation of fibers from mini-spidroins (rMaSp1R8 and rMaSp2R8) by polyelectrolyte complex formation using an anionic polyelectrolyte, gellan gum. Mini-spidroins, when treated with acetic acid and cross-linked by glutaraldehyde, formed a thin film at the interface when overlaid with a gellan gum solution. Immediate pulling of the film resulted in autofluorescent fibrous materials from either mini-spidroin alone or a combination of rMaSp1R8 and rMaSp2R8 (70:30). Addition of chitosan to the mini-spidroin solutions permitted continuous fiber production until the spinning dope supply was exhausted. When air-dried as-spun fibers were rehydrated and stretched in water, the fiber diameter decreased and the overall toughness improved. This study showed that spider silk-like fibers can be produced in large quantities through charge attraction that assembles chitosan, mini-spidroins, and gellan gum into fibrous complexes. We speculate that the spider silk self-assembly process in the duct may involve attraction of variously charged chitinous polymers, spidroins, and glycoproteins.

Dynamic Responsive Formation of Nanostructured Fibers in a Hydrogel Network: A Molecular Dynamics Study

“…The irreversible formation of oriented blocks was observed also in swollen polymers (Miyazaki et al, 2006;Peng N. et al, 2017). As well, the strain-induced crystallization is typical for some biomaterials like the above mentioned spider silk (Peng C. A. et al, 2017), collagen fibrils (Buehler, 2006) or poly-lactides (Stoclet, 2016). In this work we demonstrate that the formation of fibrillar structure can be achieved from materials with very simple micellar structure ( Figure 1E).…”

“…Tensile deformation plays a key role in the formation of biological materials, such as spider silk, where the final structure consists of nano-crystalline inclusions incorporated in the rubbery network. In fact, the drawing of fibers is frequently used in laboratory and in industry (Mondal et al, 2008;Peng C. A. et al, 2017), and has been recently improved by means of electrospinning (Svachova et al, 2016;Srivastava, 2017). The electrospinning provides stretching of material at significantly higher stretching rates than simple mechanical deformation.…”

Host Systems for the Production of Recombinant Spider Silk

“…In the case of spidroins produced using microbial hosts and transgenic mammals, wet spinning techniques are common [7]. Alternatively, fibre assembly from plant derived spidroins has been shown using gellan gum [33]. The only heterologous production system capable of spinning cocoons containing recombinant spidroins, transgenic silkworms (Bombyx mori), has been produced using a variety of gene editing techniques [44,50].…”

“…While the size of the spidroin produced is impressive, the yield of 190 mg/kg remains lower than that obtained for comparably sized spidroins in E. coli [31]. More recently, Peng and colleagues have demonstrated production of recombinant spidroins of up to 108 kDa in size in transgenic N. tabacum [32,33] However, the resulting spidroin fibres displayed tensile strengths inferior to those displayed by fibres of native N. clavipes dragline silk, and yields were well below those of microbial host systems [33].…”

A Salt Controlled Scalable Approach for Formation of Polyelectrolyte Complex Fiber†

“…Wang and coworkers also prepared multi‐colored PEC fibers by assembling DNA or histone protein with cationic conjugated polymers . Recently, new polyelectrolyte pairs, including mini‐spidroin/gellan gum and glycosaminoglycan/ collagen, were adopted for PEC fiber preparation . Besides charged polysaccharide, polypeptide and protein, the charged cellulose nanofibrils were also used for preparation of PEC fibers.…”