The Effect of Molecular Weight on the Gelation Behavior of Regenerated Silk Solutions

In Situ Mineralizing Spinning of Strong and Tough Silk Fibers for Optical Waveguides

Biopolymer-based optical waveguides with low-loss light guiding performance and good biocompatibility are highly desired for applications in biomedical photonic devices. Herein, we report the preparation of silk optical fiber waveguides through bioinspired in situ mineralizing spinning, which possess excellent mechanical properties and low light loss. Natural silk fibroin was used as the main precursor for the wet spinning of the regenerated silk fibroin (RSF) fibers. Calcium carbonate nanocrystals (CaCO₃ NCs) were in situ grown in the RSF network and served as nucleation templates for mineralization during the spinning, leading to the formation of strong and tough fibers. CaCO₃ NCs can guide the structure transformation of silk fibroin from random coils to β-sheets, contributing to enhanced mechanical properties. The tensile strength and toughness of the obtained fibers are up to 0.83 ± 0.15 GPa and 181.98 ± 52.42 MJ·m^-3, obviously higher than those of natural silkworm silks and even comparable to spider silks. We further investigated the performance of the fibers as optical waveguides and observed a low light loss of 0.46 dB·cm^-1, which is much lower than natural silk fibers. We believed that these silk-based fibers with excellent mechanical and light propagation properties are promising for applications in biomedical light imaging and therapy.

Effect of molecular weight on the structure and mechanical properties of silk sericin gel, film, and sponge

In this study, the effect of the MW on the structure and properties of sericin film, sponge, and gel was examined. As the MW of sericin increased, the gelation of the sericin aqueous solution was found to be accelerated, and the gel strength, and the gel-sol transition temperature increased. Irrespective of the casting solvent (water and formic acid) and form of sericin (gel, film, or sponge), the crystallization of the sericins was accelerated. The mechanical properties of the sericin sponge were remarkably improved upon increasing the MW of sericin. The MW of sericin almost did not have an effect on the cell toxicity. As the MW of sericin is increased, the sericin sponge becomes denser and its porosity is reduced, leading to a decrease in the swelling ratio. These results indicate that various characteristics of the sericin forms can be modulated by controlling the MW of sericin, with enhanced potential for biomedical and cosmetic applications.

In situ formation of silk-gelatin hybrid hydrogels for affinity-based growth factor sequestration and release

Facile formation of silk fibroin/gelatin-heparin hybrid hydrogels for affinity-based growth factor sequestration and release.