Influence of post-treatment with 75% (v/v) ethanol vapor on the properties of SF/P(LLA-CL) nanofibrous scaffolds

The Impact of Green Physical Crosslinking Methods on the Development of Sericin-Based Biohydrogels for Wound Healing

Silk sericin (SS)-based hydrogels show promise for wound healing due to their biocompatibility, moisture regulation, and cell proliferation properties. However, there is still a need to develop green crosslinking methods to obtain non-toxic, absorbent, and mechanically strong SS hydrogels. This study investigated the effects of three green crosslinking methods, annealing treatment (T), exposure to an absolute ethanol vapor atmosphere (V.E), and water vapor (V.A), on the physicochemical and mechanical properties of SS and poly (vinyl alcohol) (PVA) biohydrogels. X-ray diffraction and Fourier-transform infrared spectroscopy were used to determine chemical structures. Thermal properties and morphological changes were studied through thermogravimetric analysis and scanning electron microscopy, respectively. The water absorption capacity, mass loss, sericin release in phosphate-buffered saline (PBS), and compressive strength were also evaluated. The results showed that physical crosslinking methods induced different structural transitions in the biohydrogels, impacting their mechanical properties. In particular, V.A hydrogen presented the highest compressive strength at 80% deformation owing to its compact and porous structure with crystallization and bonding sites. Moreover, both the V.A and T hydrogels exhibited improved absorption capacity, stability, and slow SS release in PBS. These results demonstrate the potential of green physical crosslinking techniques for producing SS/PVA biomaterials for wound healing applications.

Formation mechanism of a novel core-shell with tetradecyl dimethyl benzyl ammonium-modified montmorillonite interlayer nanofibrous membrane and its antimicrobial properties

A novel core-shell with a tetradecyl dimethyl benzyl ammonium chloride-modified montmorillonite (TDMBA/MMT) interlayer silk fibroin (SF)/poly(lactic acid) (PLLA) nanofibrous membrane was fabricated using a simple conventional electrospinning method. Scanning electron microscopy and pore size analyses revealed that this core-shell with TDMBA/MMT interlayer maintained its nanofibrous morphology and larger pore structure more successfully than SF/PLLA nanofibrous membranes after treatment with 75% ethanol vapor. Transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses testified that the SF/PLLA-TDMBA/MMT nanofibers exhibited a core-shell with an interlayer structure, with SF/PLLA in the core-shell layer and TDMBA/MMT in the interlayer. The formation of a core-shell with interlayer nanofibers was primarily attributed to the uniform dispersion of TDMBA/MMT nanosheets in a solution owing to its exfoliation using hexafluoroisopropanol and then preparing a stable spinning solution similar to an emulsion. Compared to SF/PLLA nanofibrous membranes, the core-shell structure with TDMBA/MMT interlayers of SF/PLLA nanofibrous membranes exhibited enhanced hydrophilicity, thermal stability, mechanical properties as well as improved and long-lasting antimicrobial performance against Escherichia coli and Staphylococcus aureus without cytotoxicity.

Mechanical, structural and biodegradation characteristics of fibrillated silk fibres and papers

We characterised fibres and papers of microfibrillated silk from Bombyx mori produced by mechanical and enzymatic process. Milling increased the specific surface area of fibres from 1.5 to 8.5 m²/g and that enzymatic pre-treatment increased it further to 16.5 m²/g. These fibrils produced a uniform, significantly strong (tenacity 55 Nm/g) and stiff (Young's modulus > 2 GPa) papers. Enzymatic pre-treatment did not reduce molecular weight and tensile strength of papers but significantly improved fibrillation. Silk remained highly crystalline throughout the fibrillation process. Protease biodegradation was more rapid after fibrillation. Biodegradation was impacted by structural change due to enzymatic pre-treatment during the fibrillation. Biodegraded silk had much higher thermal degradation temperature. The unique combination of high strength, slow yet predicable degradation and controllable wicking properties make the materials ideally suited to biomedical and healthcare applications.

Silk fibroin/poly-(L-lactide-co-caprolactone) nanofiber scaffolds loaded with Huangbai Liniment to accelerate diabetic wound healing

Diabetic infection is a long-term complication difficult to cure. The skin of diabetic patients is prone to damage, the healing is slow after the injury, and the wound occurs repeatedly. Therefore, there is an urgent need to develop an effective method for treating diabetes wounds. In this study, we used the electrospinning technique to load Huangbai Liniment (Compound Phellodendron Liquid, CPL) into Silk fibroin (SF) /poly-(L-lactide-co-caprolactone) (PLCL) to prepare the nanofiber membrane (SP/CPL) to treat the diabetic wound. The morphology and structure of the nanofibers were observed by scanning electron microscope (SEM). The SEM results indicate the smooth and bead free fibers and the diameter of the fiber decreased with increasing drug concentration. The release profile indicates the sustained release of the drug. Moreover, the drug-loaded nanofibers showed inhibitory effects for S.aureus and E.coli. Furthermore, in vitro cell culture studies showed the increased proliferation and adhesion of NIH-3T3 cells on the drug-containing nanofiber membrane. Animal experiments showed that the nanofiber membrane loaded with CPL increases the expression of the TGF-β signaling pathway and collagen during wound healing, inhibits the expression of pro-inflammatory factors, and thus effectively promotes wound healing in diabetic mice. Therefore, the SP/CPL nanofiber scaffold with CPL loading is a potential candidate for diabetic wound dressings and tissue engineering.

Silk nanofibril self-assembly versus electrospinning

Natural silk fibers represent one of the most advanced blueprints for (bio)polymer scientists, displaying highly optimized mechanical properties due to their hierarchical structures. Biotechnological production of silk proteins and implementation of advanced processing methods enabled harnessing the potential of these biopolymer not just based on the mechanical properties. In addition to fibers, diverse morphologies can be produced, such as nonwoven meshes, films, hydrogels, foams, capsules and particles. Among them, nanoscale fibrils and fibers are particularly interesting concerning medical and technical applications due to their biocompatibility, environmental and mechanical robustness as well as high surface-to-volume ratio. Therefore, we introduce here self-assembly of silk proteins into hierarchically organized structures such as supramolecular nanofibrils and fabricated materials based thereon. As an alternative to self-assembly, we also present electrospinning a technique to produce nanofibers and nanofibrous mats. Accordingly, we introduce a broad range of silk-based dopes, used in self-assembly and electrospinning: natural silk proteins originating from natural spinning glands, natural silk protein solutions reconstituted from fibers, engineered recombinant silk proteins designed from natural blueprints, genetic fusions of recombinant silk proteins with other structural or functional peptides and moieties, as well as hybrids of recombinant silk proteins chemically conjugated with nonproteinaceous biotic or abiotic molecules. We highlight the advantages but also point out drawbacks of each particular production route. The scope includes studies of the natural self-assembly mechanism during natural silk spinning, production of silk fibrils as new nanostructured non-native scaffolds allowing dynamic morphological switches, as well as studying potential applications. This article is categorized under:  Biology-Inspired Nanomaterials > Peptide-Based Structures  Nanotechnology Approaches to Biology > Nanoscale Systems in Biology  Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Comparison of eri and tasar silk fibroin scaffolds for biomedical applications

The cultivated silk, mulberry, is being used as biomaterial in different forms. Eri, tasar and muga are some of the known wild silk varieties. The studies on biomedical applications of electrospun mats produced from these wild silks are limited though few studies on eri silk are available. In this work, comparison was made between eri and tasar silk fibroin scaffolds for biomedical application. The scaffolds were produced from eri silk fibroin (ESF) and tasar silk fibroin (TSF) by electrospinning method and they were treated with ethanol to improve dimensional stability. Ethanol treatment increased the crystallinity% of both ESF and TSF scaffolds. The crystallinity percentage of the ESF and TSF scaffolds was found to be 46.7 and 42.8 % respectively. Thermal stability was higher for ESF than that of TSF scaffold. The hemolytic % of ESF and TSF scaffolds was found to be 1.3 and 7.7 % respectively. The platelet adhesion on the surface of ESF scaffold was lower than that found on TSF scaffold. Better fibroblast cell attachment, binding and spreading was found on the ESF scaffold. The cell viability on ESF scaffold was 83.78 % and in TSF was 78.01 % for 48 h. The results showed that ESF electrospun scaffold can be considered as a better biomaterial for biomedical applications compared to that of TSF scaffold.

Instructive Conductive 3D Silk Foam-Based Bone Tissue Scaffolds Enable Electrical Stimulation of Stem Cells for Enhanced Osteogenic Differentiation

Stimuli-responsive materials enabling the behavior of the cells that reside within them to be controlled are vital for the development of instructive tissue scaffolds for tissue engineering. Herein, we describe the preparation of conductive silk foam-based bone tissue scaffolds that enable the electrical stimulation of human mesenchymal stem cells (HMSCs) to enhance their differentiation toward osteogenic outcomes.

Tough and VEGF-releasing scaffolds composed of artificial silk fibroin mats and a natural acellular matrix

The blend and coaxially electrospun RSF/BAMG composite scaffolds loaded VEGF exhibited good cell compatibility with improved mechanical properties.

Dual drug release electrospun core-shell nanofibers with tunable dose in the second phase

This study reports a new type of drug-loaded core-shell nanofibers capable of providing dual controlled release with tunable dose in the second phase. The core-shell nanofibers were fabricated through a modified coaxial electrospinning using a Teflon-coated concentric spinneret. Poly(vinyl pyrrolidone) and ethyl cellulose were used as the shell and core polymer matrices respectively, and the content of active ingredient acetaminophen (APAP) in the core was programmed. The Teflon-coated concentric spinneret may facilitate the efficacious and stable preparation of core-shell nanofibers through the modified coaxial electrospinning, where the core fluids were electrospinnable and the shell fluid had no electrospinnability. The resultant nanofibers had linear morphologies and clear core-shell structures, as observed by the scanning and transmission electron microscopic images. APAP was amorphously distributed in the shell and core polymer matrices due to the favorite second-order interactions, as indicated by the X-ray diffraction and FTIR spectroscopic tests. The results from the in vitro dissolution tests demonstrated that the core-shell nanofibers were able to furnish the desired dual drug controlled-release profiles with a tunable drug release amount in the second phase. The modified coaxial electrospinning is a useful tool to generate nanostructures with a tailored components and compositions in their different parts, and thus to realize the desired functional performances.

Fast disintegrating quercetin-loaded drug delivery systems fabricated using coaxial electrospinning

The objective of this study is to develop a structural nanocomposite of multiple components in the form of core-sheath nanofibres using coaxial electrospinning for the fast dissolving of a poorly water-soluble drug quercetin. Under the selected conditions, core-sheath nanofibres with quercetin and sodium dodecyl sulphate (SDS) distributed in the core and sheath part of nanofibres, respectively, were successfully generated, and the drug content in the nanofibres was able to be controlled simply through manipulating the core fluid flow rates. Field emission scanning electron microscope (FESEM) images demonstrated that the nanofibres prepared from the single sheath fluid and double core/sheath fluids (with core-to-sheath flow rate ratios of 0.4 and 0.7) have linear morphology with a uniform structure and smooth surface. The TEM images clearly demonstrated the core-sheath structures of the produced nanocomposites. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results verified that quercetin and SDS were well distributed in the polyvinylpyrrolidone (PVP) matrix in an amorphous state, due to the favourite second-order interactions. In vitro dissolution studies showed that the core-sheath composite nanofibre mats could disintegrate rapidly to release quercetin within 1 min. The study reported here provides an example of the systematic design, preparation, characterization and application of a new type of structural nanocomposite as a fast-disintegrating drug delivery system.