Water-insoluble silk films with silk I structure

Abstract

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.

Self-Organized ECM-Mimetic Model Based on an Amphiphilic Multiblock Silk-Elastin-Like Corecombinamer with a Concomitant Dual Physical Gelation Process

“…On the other hand, methanol treatment has been reported to promote the formation of β-sheets 50,51 .…”

Implantable, multifunctional, bioresorbable optics

“…S1 and S2). The dissolution time of the MPA films can be tuned by controlling the degree of crystallinity during the silk protein self-assembly process by regulating the water content within the film through an annealing step (15)(16)(17). This approach can be used to allow rapid to slow degradation of the device, depending on the application (SI Appendix, Fig.…”

Precise Protein Photolithography (P3): High Performance Biopatterning Using Silk Fibroin Light Chain as the Resist

“…It is well known that methanol treatment can promote the formation of beta sheets within the silk protein matrix 6. No noticeable variation was found in terms of the etching resistance or Young's modulus before and after the methanol treatment for all silk resist samples (Figure 4b,c).…”

“…In this context, natural silk proteins obtained from cocoons of the silkworm Bombyx mori provide “green” alternatives to synthetic materials with advantages such as superior mechanical properties (strength and toughness), outstanding biocompatibility and biodegradability, and controllable water‐solubility and degradation rate 1, 5, 6, 7…”