Artificial spinning of natural silk threads

Abstract

Silk producing arthropods spin solid fibres from an aqueous protein feedstock apparently relying on the complex structure of the silk protein and its controlled aggregation by shear forces, alongside biochemical changes. This flow-induced phase-transition of the stored native silk molecules is irreversible, environmentally sound and remarkably energy efficient. The process seemingly relies on a self-assembling, fibrillation process. Here we test this hypothesis by biomimetically spinning a native-based silk feedstock, extracted by custom processes, into silk fibres that equal their natural models’ mechanical properties. Importantly, these filaments, which featured cross-section morphologies ranged from large crescent-like to small ribbon-like shapes, also had the slender cross-sectional areas of native fibres and their hierarchical nanofibrillar structures. The modulation of the post-draw conditions directly affected mechanical properties, correlated with the extent of fibre crystallinity, i.e. degree of molecular order. We believe our study contributes significantly to the understanding and development of artificial silks by demonstrating successful biomimetic spinning relies on appropriately designed feedstock properties. In addition, our study provides inspiration for low-energy routes to novel synthetic polymers.

Mesoscale structure development reveals when a silkworm silk is spun

“…From our description above it follows that the pocket volume (as determined from SEM images) corresponds to phase-separated water. This is supported by evidence that upon exiting the spinneret natural silk fibres retain a considerable amount of water (~70%) which is mostly lost while it is drawn through the air 43 , 46 , 47 . Hence we can plot the dehydration process versus structure development as shown in Fig.…”

Tensegrity Modelling and the High Toughness of Spider Dragline Silk

“…Researchers have been trying to recreate the properties of spider silk through artificial spinning for several decades now, with mixed success, [ 9 , 46 , 47 , 48 ]. In the comprehensive review by Koeppel et al [ 49 ], the authors relayed that the general consensus across the field is that the excellent properties of many artificial silk fibres are mainly derived from a stretch-induced orientation of the fibrils, the high crystalline fraction of the material, and effective fibril linking (through the use of high molecular weight proteins).…”

Shear-Mediated Sol-Gel Transition of Regenerated Silk Allows the Formation of Janus-like Microgels

“…In fact, it has been reported that shear can induce protein aggregation, 36,37 and this effect is particularly prominent with silk-based proteins. 38 Both the spider and silkworm are capable of pulling and extruding (respectively) liquid protein from their glands and through the use of shear, a phase transition occurs which aggregates the protein into its well-known solid form. However, in the context of drug delivery, it would be particularly interesting to be able to utilise this and form capsules where the outer shell has aggregated and is solid, but internally there is still a liquid phase, i.e.…”