Aqueous Processing and Fiber Spinning of Recombinant Spider Silks

Abstract

Spiders have captured the interest of scientists for many years because spider silks are among the toughest materials, having properties that surpass some man-made synthetic materials. Spinning recombinant silk to duplicate those properties has proved to be extremely difficult. This is the first known report of spinning recombinant silk fibers in an aqueous environment. The method seeks to keep the protein soluble throughout the process, not unlike the way the spider stores and spins silk. Recombinant silk proteins were produced by bacterial fermentation in which the cell pellets were lyophilized and lysed with organic acid. Silk protein was purified from the lysate by chromatography and processed in dilute denaturing buffer into a fiber spinning solution. Circular dichroism measurements of the silk solutions revealed an increase in β-sheet content as a function of time. Time-dependent self-association of silk protein was monitored in solution by dynamic light scattering. Furthermore, the observed increase in β-sheet content and self-association appear to be required for fiber formation. Recombinant silk fibers were 10−60 μm in diameter, water insoluble, and birefringent, indicating molecular orientation within the fiber.

The elaborate structure of spider silk

“…Other attempts using special postspinning techniques yielded silks with even larger diameters. 62,69 Until now, even the best mechanical properties obtained by artificial spinning techniques are much lower than that of natural dragline silks. 68 Exceeding nature-proteins as polymer materials.…”

Spider silk as a blueprint for greener materials: a review

“…The fiber so obtained can further be post-drawn, 126,196,[200][201][202][203] a treatment that is one of the favored and most efficient strategies to increase the level of molecular orientation and improve materials' mechanical response. The formation of any spidroin-based material follows essentially the same procedures than those used for the production of fibers in vitro.…”

Characterization of natural and biomimetic spider silk fibers

“…Previously published data on fi bers made of recombinant silk proteins were obtained by wet spinning out of organic solvents or by spinning into a coagulation bath, or using both Arcidiacono et al, 2002;Lazaris et al, 2002;Teulé et al, 2007Teulé et al, , 2011Xia et al, 2010). Interestingly, our fi bers, obtained by an all-aqueous production process, reveal diameters between 7-16 μm without postspin drawing, being signifi cantly thinner than that of other artifi cial silks which reach such dimensions only after application of a postspin stretching (Table 2).…”

“…As technically mimicking the natural spinning process has been problematic (Heim et al, 2009;Lazaris et al, 2002;Viney et al, 1994Viney et al, , 2000Vollrath et al, 1998;Vollrath andKnight, 1999, 2001), most studies have focused on the application of established technical spinning procedures such as wet spinning Arcidiacono et al, 2002;Elices et al, 2011a;Lazaris et al, 2002;Seidel et al, 1998Seidel et al, , 2000Sohn and Gido, 2009;Xia et al, 2010). All of these approaches, despite using different spinning techniques and postspinning processes, have resulted in fi bers with inferior properties in comparison to natural fi bers.…”