Insoluble and Flexible Silk Films Containing Glycerol

Abstract

We directly prepared insoluble silk films by blending with glycerol and avoiding the use of organic solvents. The ability to blend a plasticizer like glycerol with a hydrophobic protein like silk and achieve stable material systems above a critical threshold of glycerol is an important new finding with importance for green chemistry approaches to new and more flexible silk-based biomaterials. The aqueous solubility, biocompatibility, and well-documented use of glycerol as a plasticizer with other biopolymers prompted its inclusion in silk fibroin solutions to assess impact on silk film behavior. Processing was performed in water rather than organic solvents to enhance the potential biocompatibility of these biomaterials. The films exhibited modified morphologies that could be controlled on the basis of the blend composition and also exhibited altered mechanical properties, such as improved elongation at break, when compared with pure silk fibroin films. Mechanistically, glycerol appears to replace water in silk fibroin chain hydration, resulting in the initial stabilization of helical structures in the films, as opposed to random coil or beta-sheet structures. The use of glycerol in combination with silk fibroin in materials processing expands the functional features attainable with this fibrous protein, and in particular, in the formation of more flexible films with potential utility in a range of biomaterial and device applications.

Silk scaffolds for musculoskeletal tissue engineering

“…28 Fabrication of silk films by a layer-by-layer technique has also reported. 29 Additionally, silk films formed by LangmuirBlodgett and spin coating have been obtained. 30,31 As most SF remains random coil structure, the stability of Figure 1 Representative biomaterial scaffolds fabricated from silk and silk fibroin solution for MTE: braided silk cords, 9 knitted silk nets, 19 silk fibroin films, 20 silk fibroin microparticles, 21 electrospun silk fibroin nanofibers, 22 3D porous silk fibroin sponges, 23,24 and silk fibroin hydrogels.…”

“…Besides, certain pretreatment of the silk solution can also obtain waterinsoluble films, such as controlled drying process 26 or adding glycerinum to the SF solution. 29 Particles SF particles can be produced by freeze drying the SF solution or milling the solid SF into micro/nanoparticles. 34 Fabrication of silk particles by self-assembly, freezethawing, jet breaking, or spray drying is also reported.…”

Application of Insoluble Fibroin Film as Conditioning Film for Biofilm Formation

“…(19) Most recently, Lu et al have demonstrated that the use of glycerol in combination with silk fibroin provides important benefits to the film properties. (20) Since the fibroin film has excellent biocompatibility and bioabsorbability, and a low level of inflammatory potential, it has been studied as a scaffold for tissue engineering, (21)(22)(23) and a material for enzyme stabilization. (24,25) Thus, the application of insoluble fibroin film for the formation of biofilms and immobilization of microbes on the surface is expected.…”

Formulation and Characterization of Silk Fibroin Films as a Scaffold for Adipose-Derived Stem Cells in Skin Tissue Engineering

“…De-gummed fibers of silk fibroin can be used as they are or can be regenerated in order to obtain an aqueous fibroin solution. The regenerated fibroin is then processed in different ways to produce adequate scaffolds (13,20,(26)(27)(28) (24,32), and glycerol (33). The pectin, a natural polysaccharide polymer constituting the plant cell wall, has been recently employed for several biomedical applications, including drug and gene delivery, wound healing and tissue engineering; in particular, pectin hydrogels were used for bone tissue regeneration, as prosthetic nucleus pulposus substitutes or as wound healing patches (34).…”

“…The pectin, a natural polysaccharide polymer constituting the plant cell wall, has been recently employed for several biomedical applications, including drug and gene delivery, wound healing and tissue engineering; in particular, pectin hydrogels were used for bone tissue regeneration, as prosthetic nucleus pulposus substitutes or as wound healing patches (34). Glycerol is a plasticizer and has been added to fibroin by Lu et al (33) to obtain insoluble and flexible films, improving their mechanical properties when compared with pure silk fibroin films; The aim of this work is to prepare silk fibroin films for ADSCs culture as a novel feeder layer for skin tissue engineering. Pectin has been added to promote the protein conformational transition and construct strength, while glycerol as plasticizer, providing biomaterial flexibility.…”