Photothermal Regenerated Fibers with Enhanced Toughness: Silk Fibroin/MoS2 Nanoparticles

The distinctive mechanical and photothermal properties of Molybdenum sulfide (MoS2) have the potential for improving the functionality and utilization of silk products in various sectors. This paper reports on the preparation of regenerated silk fibroin/molybdenum disulfide (RSF/MoS2) nanoparticles hybrid fiber with different MoS2 nanoparticles contents by wet spinning. The simulated sunlight test indicated that the temperature of 2 wt% RSF/MoS2 nanoparticles hybrid fibers could rise from 20.0 °C to 81.0 °C in 1 min and 98.6 °C in 10 min, exhibiting good thermal stability. It was also demonstrated that fabrics made by manual blending portrayed excellent photothermal properties. The addition of MoS2 nanoparticles could improve the toughness of hybrid fibers, which may be since the mixing of MoS2 nanoparticles hindered the self-assembly of β-sheets in RSF solution in a concentration-dependent manner because RSF/MoS2 nanoparticles hybrid fibers showed a lower β-sheet content, crystallinity, and smaller crystallite size. This study describes a new way of producing high toughness and photothermal properties fibers for multifunctional fibers’ applications.

Electrospun regenerated silk fibroin is a promising biomaterial for the maintenance of inner ear progenitors in vitro

Objective We sought to determine the biocompatibility of electrospun regenerated silk fibroin (RSF) mats with inner ear progenitors, especially their effect on the differentiation of inner ear progenitors into hair cells. Methods Neonatal mouse cochleae (n = 20) were collected and digested and allowed to form spheres over several days. Cells digested from the spheres were then seeded onto aligned or random RSF mats, with laminin-coated coverslips serving as controls. The inner ear progenitor cell mortality was examined by TUNEL labeling, and the adhesion of cells to the RSF mats or coverslip was determined by scanning electron microscopy. Finally, the number of hair cells that differentiated from inner ear progenitors was determined by Myosin7a expression. Unpaired Student’s t-tests and one-way ANOVA followed by a Dunnett’s multiple comparisons test were used in this study ( p < 0.05). Results After 5 days of culture, the inner ear progenitors had good adhesion to both the aligned and random RSF mats and there was no significant difference in TUNEL+ cells between the mats compared to the coverslip ( p > 0.05). After 7 days of in vitro differentiation culture, the percentage of differentiated hair cells on the control, aligned, and random RSF mats was 2.5 ± 0.5%, 2.7 ± 0.4%, and 2.4 ± 0.2%, respectively, and there was no significant difference between Myosin7a+ cells on either RSF mat compared to controls ( p > 0.05). Conclusion The aligned and random RSF mats had excellent biocompatibility with inner ear progenitors and helped the inner ear progenitors maintain their stemness. Our results thus indicate that RSF mats represent a useful scaffold for the development of new strategies for inner ear tissue engineering research.

Fractionation of Regenerated Silk Fibroin and Characterization of the Fractions

The molecular weight (MW) of regenerated silk fibroin (RSF) decreases during degumming and dissolving processes. Although MW and the MW distribution generally affect polymer material processability and properties, few reports have described studies examining the influences of MW and the distribution on silk fibroin (SF) material. To prepare different MW SF fractions, the appropriate conditions for fractionation of RSF by ammonium sulfate (AS) precipitation process were investigated. The MW and the distribution of each fraction were found using gel permeation chromatography (GPC) and SDS-polyacrylamide electrophoresis (SDS-PAGE). After films of the fractionated SFs formed, the secondary structure, surface properties, and cell proliferation of films were evaluated. Nanofiber nonwoven mats and 3D porous sponges were fabricated using the fractionated SF aqueous solution. Then, their structures and mechanical properties were analyzed. The results showed AS precipitation using a dialysis membrane at low temperature to be a suitable fractionation method for RSF. Moreover, MW affects the nanofiber and sponge morphology and mechanical properties, although no influence of MW was observed on the secondary structure or crystallinity of the fabricated materials.

A Fast and Reliable Process to Fabricate Regenerated Silk Fibroin Solution from Degummed Silk in 4 Hours

Silk fibroin has a high potential for use in several approaches for technological and biomedical applications. However, industrial production has been difficult to date due to the lengthy manufacturing process. Thus, this work investigates a novel procedure for the isolation of non-degraded regenerated silk fibroin that significantly reduces the processing time from 52 h for the standard methods to only 4 h. The replacement of the standard degumming protocol by repeated short-term microwave treatments enabled the generation of non-degraded degummed silk fibroin. Subsequently, a ZnCl2 solution was used to completely solubilize the degummed fibroin at only 45 °C with an incubation time of only 1 h. Desalting was performed by gel filtration. Based on these modifications, it was possible to generate a cytocompatible aqueous silk fibroin solution from degummed silk within only 4 h, thus shortening the total process time by 48 h without degrading the quality of the isolated silk fibroin solution.