Water-Insoluble Silk Films with Silk I Structure

By Q. Lu, Xiao Hu, Xiaoqin Wang, J. Kluge, Shenzhou Lu, P. Cebe, David Kaplan. Acta Biomaterialia, 2009

596 citations recorded by the source corpus.

Water-insoluble regenerated silk materials are normally achieved by increasing β-sheet content (silk II). In the present study, water-insoluble silk films were prepared by controlling very slow drying of B. mori silk solutions, resulting in the formation of stable films with dominating silk I instead of silk II structure. Wide angle x-ray scattering (WAXS) indicated that the silk films stabilized by slow drying were mainly composed of silk I rather than silk II, while water- and methanol-annealed silk films had a higher silk II content. The silk films prepared through slow drying had a globule-like structure in the core with nano-filaments. The core region was composed of silk I and silk II, and these regions are surrounded by hydrophilic nano-filaments containing random, turns, and α-helix secondary structures. The insoluble silk films prepared by slow drying had unique thermal, mechanical and degradative properties. DSC results revealed that silk I crystals had stable thermal properties up to 250°C, without crystallization above the Tg, but degraded in lower temperature than silk II structure. Compared with water- and methanol-annealed films, the films prepared through slow drying achieved better mechanical ductility and more rapid enzymatic degradation, reflective of the differences in secondary structure achieved via differences in post processing of the cast silk films. Importantly, the silk I structure, a key intermediate secondary structure for the formation of mechanically robust natural silk fibers, was successfully generated in the present approach of very slow drying, mimicking the natural process. The results also point to a new mode to generate new types of silk biomaterials, where mechanical properties can be enhanced, and degradation rates increased, yet water insolubility is maintained along with low beta sheet content.

Subfields: Biomaterials, Insect Science

View Paper: https://www.semanticscholar.org/paper/f8faa9cabb075825bf057aa778acdc3b0ea7e9e4

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In Biomaterials

1. S. Kundu
2. Fiorenzo G. Omenetto
3. David Kaplan
4. B. Kundu
5. Xungai Wang
6. S. Hofmann
7. J. Melke
8. Keita Ito

In Insect Science

1. David Kaplan

Citations in the corpus

• Dissolvable Films of Silk Fibroin for Ultrathin, Conformal Bio-Integrated Electronics (2010, background): “, mechanically robust and flexible in thin-film for”
• Silk fibroin as biomaterial for bone tissue engineering. (2016, methodology): “9 content which resulted in the fastest degradation [74].”
• Silk fibroin biomaterials for tissue regenerations. (2013, methodology): “As stability of such cast films is low, techniques like controlled drying [85], water annealing [49], stretching [86], and alcohol immersion are used to improve β-sheet crystallinity.”