Structure and properties of biomedical films prepared from aqueous and acidic silk fibroin solutions

Abstract

Silk fibroin films are promising materials for a range of biomedical applications. To understand the effects of casting solvents on film properties, we used water (W), formic acid (FA), and trifluoroacetic acid (TFA) as solvents. We characterized molecular weight, secondary structure, mechanical properties, and degradation behavior of cast films. Significant degradation of fibroin was observed for TFA-based film compared to W and TA-based films when analyzed by SDS-PAGE. Fibroin degradation resulted in a significant reduction in tensile strength and modulus of TFA-based films. Compared to water, TFA-based films demonstrated lower water solubility (19.6% vs. 62.5% in 12 h) despite having only a marginal increase in their β-sheet content (26.9% vs. 23.7%). On the other hand, FA-based films with 34.3% β-sheet were virtually water insoluble. Following solubility treatment, β-sheet content in FA-based films increased to 50.9%. On exposure to protease XIV, water-annealed FA-based films lost 74% mass in 22 days compared to only 30% mass loss by ethanol annealed FA films. This study demonstrated that a small variation in the β-sheet percentage and random coil conformations resulted in a significant change in the rates of enzymatic degradation without alteration to their tensile properties. The film surface roughness changed with the extent of enzymatic hydrolysis.

Milled non-mulberry silk fibroin microparticles as biomaterial for biomedical applications

“…In our previous reports, an effective and reproducible method was developed for the preparation of silk fibroin ultrafine particles based on a top-down approach using a combination of wetmilling and spray-drying method [40][41][42][43]. This fabrication method is rather simple and reproducible, which allows the production of biocompatible materials with high encapsulation efficiencies [44].…”

Tympanic Membrane Organ Culture using Cell Culture well Inserts Engrafted with Tympanic Membrane Tissue Explants

“…Silk fibroin materials have effective mechanical properties for TM tissue engineering (21) and provide a suitable substrate for human TM keratinocytes (18). In order to test whether these TM cells would support a tissue-engineering approach, we cultured explant-derived cells on porous silk membrane scaffolds (Supplementary Figure S3A).…”

Bioengineered silk scaffolds in 3D tissue modeling with focus on mammary tissues

“…Silk fibroin possesses an anti-thrombotic surface with good resistance to high shear stress and blood flow pressure [183]. Despite high tensile strength of native silk fibers (0.5-0.6 GPa), the [181,182] tensile strengths of materials prepared from regenerated silk fibroin solution are significantly weaker (~0.02 GPa for dry silk films) [183,196], in part because of the loss of secondary structure in processed silk.…”