Silk scaffolds achieved using pickering high internal phase emulsion templating and ionic liquids

We describe a convenient route to the preparation of silk scaffolds that does not require silk fiber dissolution and regeneration. We prepare the silk scaffolds via a single step pickering-high internal phase emulsion (HIPE) method. Additionally, we find that the use of biocompatible ionic liquids significantly improves the compressive properties of the HIPEs.

Silk powder: production, characterisation, and application

 For the first time, produced silk particles with unique properties in the range of 7 µm – 200 nm using milling process which opens up new opportunities for silk particle for diverse applications especially drug delivery and tissue scaffolds.

Surface energy of silk fibroin and mechanical properties of silk cocoon composites

Silkworm cocoons are biological composite structures protecting the silkworms against environmental damage and physical attack by natural predators. In particular, some outdoor reared silk cocoons exhibit outstanding mechanical properties that are relevant to the higher level protection required to enhance the survival chance of silkworms while supporting their metabolic activity. The performance of composite materials strongly depends on the adhesion between the fiber reinforcement and matrix, with the surface properties of the fibers playing a key role in determining the level of adhesion achieved. For this reason it is important to study the surface properties of silk fibroin to further understand the composite properties of the cocoons. In this work, both the mechanical properties of the silk cocoons and silk fibroin were studied. The surface topography was examined using scanning probe microscopy (SPM), which revealed distinct longitudinal ridges and striations along the fiber axis of the four silk fiber types. The fibers were found to exhibit heterogeneity in surface energy as evidenced from inverse gas chromatography (IGC) measurements. The combination of excellent mechanical properties and the more energetically heterogeneous surface nature of the wild A. pernyi silk fibroin fibers correlates well with the excellent mechanical properties of the A. pernyi cocoons. This journal is

Effect of solvent on ionic liquid dissolved regenerated antheraea assamensis silk fibroin

We report on the dissolution of semi-domestic silk type Antheraea assamensis using ionic liquids. We investigated the impact of different coagulating solvents, including isopropanol and water on the structure and the morphology of the regenerated silk. We found that the water regenerated silk film showed a high β-sheet content and a native silk-like XRD pattern.

Relationship between processing, surface energy and bulk properties of ultrafine silk particles

Silk particles of different sizes and shapes were produced by milling and interactions with a series of polar and non-polar gaseous probes were investigated using an inverse gas chromatography technique. The surface energy of all silk materials is mostly determined by long range dispersive interactions such as van der Waals forces. The surface energy increases and surface energy heterogeneity widens after milling. All samples have amphoteric surfaces and the concentration of acidic groups increases after milling while the surfaces remain predominantly basic. We also examined powder compression and flow behaviours using a rheometer. Increase in surface energy, surface area, and static charges in sub-micron air jet milled particles contributed to their aggregation and therefore improved flowability. However they collapse under large pressures and form highly cohesive powder. Alkaline hydrolysis resulted in more crystalline fibres which on milling produced particles with higher density, lower surface energy and improved flowability. The compressibility, bulk density and cohesion of the powders depend on the surface energy as well as on particle size, surface area, aggregation state and the testing conditions, notably the consolidated and unconsolidated states. The study has helped in understanding how surface energy and flowability of particles can be changed via different fabrication approaches.

Microstructure and mechanical properties of silk from different components of the Antheraea pernyi cocoon

Silk fibres from different components of the Antheraea pernyi silkworm cocoon, namely peduncle, outer floss, and cocoon shells (outermost layer and pelade layer) were studied in detail to gain insights into the structure-property-function relationship. Among the fibres from different components, peduncle fibres are the softest with the largest viscoelastic lag, which may reduce the oscillation amplitude when a cocoon hangs on a twig. Fibres from the outermost layer are the toughest and have the largest breaking energy. Outer floss fibres have the highest content of sericin (about 11.98%) but their hardness and elasticity are intermediate. Pelade fibres are shape - preservable and stable with superior hardness and elasticity. The understanding of the properties of different silk fibres is essential for understanding their respective roles in the function of a silk cocoon and will also inspire new designs of protective materials under stringent environmental conditions.

Comparison of milling and solution approach for production of silk particles

Silk particles were produced by regenerating from silk solution, and using a milling method. In the regenerated silk particle production, two methods which are reported to render submicron silk particles were selected. Their particle sizes and structures were compared with particles of milling method already developed by us. The volume median average particle sizes (d(0.5)) of regenerated particles were much higher than what was reported previously. In contrast, milling method could produce particles with adjustable particle sizes ranging from micron to submicron level. All the milled particles had advantage of at least 15. °C higher thermal decomposition temperature than regenerated particles. They had silk II structure, and the crystallinity reduced as particle fineness increased, but remained higher than regenerated particles of similar sizes. © 2014 Elsevier B.V.

Green electrospun pantothenic acid/silk fibroin composite nanofibers: fabrication, characterization and biological activity

Silk fibroin (SF) from Bombyx mori has many established excellent properties and has found various applications in the biomedical field. However, some abilities or capacities of SF still need improving to meet the need for using practically. Indeed, diverse SF-based composite biomaterials have been developed. Here we report the feasibility of fabricating pantothenic acid (vitamin B5, VB5)-reinforcing SF nanofibrous matrices for biomedical applications through green electrospinning. Results demonstrated the successful loading of D-pantothenic acid hemicalcium salt (VB5-hs) into resulting composite nanofibers. The introduction of VB5-hs did not alter the smooth ribbon-like morphology and the silk I structure of SF, but significantly decreased the mean width of SF fibers. SF conformation transformed into β-sheet from random coil when composite nanofibrous matrices were exposed to 75% (v/v) ethanol vapor. Furthermore, nanofibers still remained good morphology after being soaked in water environment for five days. Interestingly, as-prepared composite nanofibrous matrices supported a higher level of cell viability, especially in a long culture period and significantly assisted skin cells to survive under oxidative stress compared with pure SF nanofibrous matrices. These findings provide a basis for further extending the application of SF in the biomedical field, especially in the personal skin-care field.

In-situ synthesis of gold nanoparticles for multifunctionalization of silk fabrics

A simple in-situ synthesis route for gold nanoparticles (NPs) was developed to realize multifunctions for silk fabrics. The gold NPs were prepared in a heated solution containing white silk fabric samples. The silk fabrics were colored red and brown by the gold NPs because of their localized surface plasmon resonance (LSPR) property. Gold nanospheres on silk were obtained at a low gold content, and gold nanoplates were synthesized as the gold content increased. The silk fabrics treated with gold NPs showed good light fastness. Moreover, the gold NPs endowed silk fabrics with strong antibacterial activity, excellent UV protection property and enhanced thermal conductivity. © 2013 Elsevier Ltd. All rights reserved.

Structure and characteristics of milled silk particles

This study examined the structure, thermal property, and ion adsorption of silk particles. The particles were prepared by attritor-bead mill combination, using alkaline (pH10) charge repulsion and surfactant steric repulsion methods. Both methods produced particles with a dominant β-sheet structure, similar to the silk fibre. There was no significant difference in the decomposition temperatures for either the silk fibre or the micro/nano silk particles. An important finding from this study is clear evidence of reduction of amorphous content during the final stage of powdering using the bead mill. As a result, despite reduction in β-sheet crystallites with the progressive milling, the relative β-sheet content actually increased during this process. However, intermolecular forces between the β-sheets reduced significantly and hence the XRD results showed significant reduction in crystallinity in nano silk particles but crystal forming segments remained with β-sheet conformations after milling. The structural change influenced the ion-adsorption property where particle-size reduction resulted in a significant increase in both the rate and volume of HCrO4- adsorption. © 2014 Elsevier B.V.

Silk films as a repair material for perforations of the tympanic membrane

Large, chronic perforations of the tympanic membrane or eardrum can cause hearing loss as well as a range of secondary health problems. Current methods of repair usually involve grafting a material such as cartilage from another site on the body across the perforation. However, given problems such as possible infections at the graft donor site and the inability to see through the graft to assess infection within the middle ear, there is a need to develop an alternative material that is strong, readily available and transparent. Such a material would allow for less invasive surgery and potentially result in a superior hearing outcome for the patient. Our recent work has identified silk fibroin films as a promising material for this application. This paper reviews the repair of large perforations and compares the mechanical properties of silk with some existing graft materials. It also briefly discusses the difficulties in defining and comparing these properties with such different materials.