Gelation of <i>Antheraea pernyi</i> Silk Fibroin Accelerated by Shearing

Abstract

The rapid manufacture of silk fibroin gels in mild conditions is an important subject in the field of silk-based biomaterials. In this study, the gelation of Antheraea pernyi silk fibroin (ASF) aqueous solution was induced by shearing, without chemical cross-linking agents. Simple shearing controlled and accomplished the steady and rapid conformational transition to β-sheets with ease. The conformational transformation and rapid gelation mechanisms of ASF induced by shearing were tracked and analyzed by circular dichroism spectrometry, Fourier transform infrared spectroscopy and X-ray diffractometry, then compared with Bombyx mori silk fibroin (BSF). ASF quickly formed hydrogels within 24-48 h after shearing under different shearing rates for 30-90 min, resulting in sol-gel transformation when the β-sheet content reached nearly 50%, which is the minimum content needed to maintain a stable hydrogel system in ASF. The gel structures remained stable once formed. The rapid gelation of ASF through shearing compared with BSF was achieved because of ASF's alternating polyalanine-containing units, which tend to form α-helix structures spontaneously. Further, the entropic cost during the conformational transition from the α-helix to the β-sheet structure is less than the cost of the transition from the random coil structure. This method is a simple, non-chemical cross-linking approach for the promotion of rapid gelation and the protection of the biological properties of ASF, and it may prove useful for application in the field of biomedical materials.

Development of bone scaffold from in situ forming hydrogel of Thai silk fibroin and collagen

“…Even though it was reported that shearing force could decrease gelation time of SF solution, the effect was significant in SF solution from A. pernyi rather than SF solution from B. mori. Twenty-two to forty-eight hours were needed for SF gelation with shearing for 30-90 minutes at 280-480 rpm [80]. Not only the impractical long period of gelation time is needed, but also massive bubble formation within the solution found after shearing with homogenizer probe makes this method not a suitable way for induction of SF hydrogel for our work.…”