Replicating shear-mediated self-assembly of spider silk through microfluidics

The development of artificial spider silk with properties similar to native silk has been a challenging task in materials science. In this study, we use a microfluidic device to create continuous fibers based on recombinant MaSp2 spidroin. The strategy incorporates ion-induced liquid-liquid phase separation, pH-driven fibrillation, and shear-dependent induction of beta-sheet formation. We find that a threshold shear stress of approximately 72 Pa is required for fiber formation, and that beta-sheet formation is dependent on the presence of polyalanine blocks in the repetitive sequence. The MaSp2 fiber formed has a beta-sheet content (29.2%) comparable to that of native dragline with a shear stress requirement of 111 Pa. Interestingly, the polyalanine blocks have limited influence on the occurrence of liquid-liquid phase separation and hierarchical structure. These results offer insights into the shear-induced crystallization and sequence-structure relationship of spider silk and have significant implications for the rational design of artificially spun fibers. Native spider silk has desirable mechanical properties, but these are challenging to replicate in an artificial material. Here, the authors report the use of a microfluidic system to create continuous fibers based on recombinant spidroin.