Fabrication Of Silk Research Articles

Fabrication of silk fibroin/poly(lactic-co-glycolic acid)/graphene oxide microfiber mat via electrospinning for protective fabric.

In this study, a biodegradable silk fibroin/poly(lactic-co-glycolic acid)/graphene oxide (SF/PLGA/GO) microfiber mat was successfully fabricated via electrospinning for use in protective fabrics. The morphology of the microfiber mat was characterized by Scanning Electron Microscope (SEM). The thermal and mechanical properties, water contact angle, surface area and pore size of the microfiber mats were characterized. Due to the introduction of graphene which can interact with silk fibroin, the SF/PLGA/GO microfiber mat, compared with the silk fibroin/poly (lactic-co-glycolic acid) (SF/PLGA) microfiber mat, has higher strength, greater Young's modulus and better thermal stability which can meet the requirements of protective fabric. The microfiber mat is biodegradable because its main component is silk fibroin and PLGA. In particular, the microfiber mat has a small pore size range of 4 ∼ 10 nm in diameter, a larger surface area of 2.63 m2 g-1 and pore volume of 7.09 × 10-3 cm3 g-1. The small pore size of the mat can effectively block the particulate pollutants and pathogenic particles in the air. The larger surface area and pore volume of the mat are effective for breathability. Therefore, the fabricated SF/PLGA/GO microfiber mat has great application potentials for protective fabrics.

Fabrication and Characterization of Silk Fibroin/Curcumin Sustained-Release Film.

In the present work, a sustained-release film composed of silk fibroin (SF), curcumin (Cur), glutaraldehyde (GA), and glycerol (Gly) was prepared successfully for wound dressings. Features relevant to wound dressings of SF/Gly/GA/Cur film were assessed. Physical and chemical properties of the fabricated materials were also characterized. The results showed that the prepared SF/Gly/GA/Cur film demonstrated a good sustained-release performance, flexibility, and gas permeability. In addition, it was found that the prepared SF/Gly/GA/Cur film possessed the capability to effectively inhibit the growth of bacteria and prevent bacterial penetration with a suitable water vapor transmission rate. Furthermore, the prepared composite film was non-cytotoxic, which makes it an ideal material for wound dressings.

Design and Fabrication of Silk Templated Electronic Yarns and Applications in Multifunctional Textiles

Summary E-textiles are of interest in a variety of fields, such as wearable electronics and real-time healthcare monitoring. Critical challenges remain, related to design and fabrication techniques to meet the varied requirements for e-textiles. As an ancient and incomparable textile fiber, natural silk fibers can be considered to address these issues. However, processing challenges have thus far precluded the realization of electrically conducting natural silks. Here, we report a scalable dip-coating strategy to construct conductive silk fibers (CSFs). Natural silk fibers were functionalized by a tailor-made carbon nanotube (CNT) paint, which selectively etches the surface of the silk fibers without destroying the internal structure of the fibers. The CSFs maintained the properties of both the silks and CNTs, with high mechanical performance, super-hydrophobicity, solvent resistance, and thermal sensitivity. The CSFs can be automatically woven into fabrics, resulting in textiles sensitive to surrounding physical stimuli, including force, strain, temperature, and solvents.

Fabrication and Characterization of Electrospun Silk Fibroin/Gelatin Scaffolds Crosslinked With Glutaraldehyde Vapor

Bombyx mori silk fibroin (SF) /gelatin nanofibre mats with different blend ratios of 100/0, 90/10 and 70/30 were prepared by electrospinning and crosslinked with glutaraldehyde (GTA) vapour at room temperature. GTA was shown to induce the conformational transition of SFs from random coils to β-sheets along with increasing nanofibre diameters with the addition of gelatin into SFs. It was found that by increasing the gelatin content, crosslinking degree was enhanced from 34% for pure SF nanofibre mats to 43% for SF/gelatin counterparts at the blend ratio of 70/30, which directly affected mechanical properties, porosity, and water uptake capacity (WUC) of prepared nanofibre mats. The addition of 10 and 30 wt% gelatin into SFs improved tensile strengths of SF/gelatin nanofibre mats by 10 and 27% along with significant increases in Young’s modulus by 1.1 and 1.3 times, respectively, as opposed to plain SF counterparts. However, both porosity and WUC were found to decrease from 62 and 405% for pristine SF nanofibre mats to 47% and 232% for SF/gelatin counterparts at the blend ratio of 70/30 accordingly. To further evaluate the combined effect of GTA crosslinking and gelatin content on biological response of SF/gelatin scaffolds, the proliferation assay using 3T3 mouse fibroblast was conducted. In comparison with pure SFs, cell proliferation rate was lower for SF/gelatin constructs, which declined when the gelatin content increased. These results indicated that the adverse effect of GTA crosslinking on cell response may be ascribed to imposed changes in morphology and physiochemical properties of SF/gelatin nanofibre mats. Although crosslinking could be used to improve mechanical properties of nanofibre mats, it reduced their capacity to support the cell activity. GTA optimisation is required to further modulate the physico-chemical properties of SF/gelatin nanofibre mats in order to obtain stable materials with favourable bioactive properties and promote cellular responses for tissue engineering applications.

A Facile Measurement for Monitoring Dragline Silk Dope Concentration in Nephila pilipes upon Spinning.

In spite of all the efforts towards deciphering the silk spinning process of spiders, the underlying mechanism is yet to be fully revealed. In this research, we designed a novel approach that allowed us to quantitatively evaluate the concentration change of silk dope during the liquid-to-solid spinning process of the orb-weaver Nephila pilipes. As a prior characterization of the optimal silking conditions, we first gauged the influence of silking-rate, ranging from 1.5 to 8.0 m/min, on dragline silk diameters and silk tensile strengths obtained from the spiders. Next, to evaluate the liquid content of the silk dope, the major ampullate gland was dissected and the concentration of the sac portion was measured by thermogravimetric analysis (TGA). The solid content of the dragline fibers leaving the spinneret was investigated by calculating the ratio of collected dried silk to the weight loss of the spider recorded in situ upon spinning. As the results indicate, the tensile strength and diameter of the spun dragline fibers were 800–1100 MPa and 8–11 μm, respectively. The liquid content of silk stored in the major ampullate sac (50.0 wt%) was significantly lower than that of silk leaving the spinnerets (80.9–96.1 wt%), indicating that a liquid supplying mechanism might be involved during the spinning process. This reveals, for the first time, quantitative evidence in support of the lubricative hypothesis proposed formerly, namely that a liquid coating layer is supplemented to compensate for silking resistance during the spinning process of a spider. The spigot, at the exit of the spinneret, is speculated to serve as a valve-like controller that regulates the lubrication process along with fiber formation. Taken together, these findings provide understanding of the physiological functions in the spider spinning process and could further shed some light on the future biomimetic development of silk material fabrication.

Electrospun SF/PVA Nanofiber Filters for Highly Efficient PM $_{2.5}$ Capture

Particulate matter (PM) air pollution is associated with various adverse health effects. Heavy outdoor air pollution, especially smog, has significantly impacted the living quality of residential environments. Here, we report the fabrication of silk fibroin/polyvinyl alcohol (SF/PVA) nanofiber air filters for the filtration of PM pollution using the electrospinning technique. Silk fibroin is a type of protein fibers, which is widely available with excellent environmental sustainability, and PVA is commonly used for continuous nanofiber fabrication. Our results showed that the PM $_{2.5}$ removal efficiency of the SF/PVA filter was 99.11 ${\bf \pm }$ 0.24%, which was about 10% higher than that of the pure PVA filter under the same pressure drop of 50 Pa. In a 24-h filtration test, the filtration efficiency of this composite SF/PVA filter remained at a high value of 98.97% after 24 h. The results indicate the superior filtration performance of the SF/PVA nanofiber air filter, which holds a great promise in PM pollution prevention.

A preliminary study on the fabrication of silk fibroin/chitosan/nano-hydroxyapatite osteochondral scaffolds with a gradient pore size structure

Objective To explore the feasibility and methods of preparing silk fibroin(SF)/chitosan(CS)/nano-hydroxyapatite(nHA)composite osteochondral scaffolds with a gradient pore size structure. Methods We prepared an SF solution, a CS solution and an nHA suspension, all with a 2% concentration, and mixed them with equal proportions.The mixture was used to prepare SF/CS/nHA composite osteochondral scaffolds with a pore size gradient through a centrifugal-freeze drying and chemical cross-linking method.The porosity, hot-water loss rate, water swelling rate and mechanical properties of the scaffold were measured, and the dissolution curve and stress-strain curve were drawn.The internal structure and morphology of the scaffold were observed by scanning electron microscopy(SEM)and the sizes of pores in the scaffold were measured. Results The porosity of the scaffold was(91.30±3.35)%; The five-week hot water loss rate was(16.57±3.18)%; And the water swelling rate was(3218.53±84.37)%.Mechanical test results demonstrated a good compression performance of the scaffold.SEM showed that the internal pores of the scaffolds were honeycomb-structured with communicating passages; The density of pores gradually increased with decreasing pore sizes from the top to the bottom(pore sizes at four different levels: (141.11±11.85)μm, (119.94±9.05)μm, (93.10±14.98)μm, and(79.95±8.65)μm, respectively, F=22.973, P=0.000). Scaffold cytotoxicity test results indicated no significant difference between A values of the extract group and of the negative control group at any time point(t24 h=0.520, P=0.610; t48 h=0.665, P=0.515; t72 h=0.439, P=0.666), and all RGR values were greater than 100%. Conclusions SF/CS/nHA composite osteochondral scaffolds with a gradient pore size structure can be prepared with a centrifugal-freeze drying and chemical cross-linking method.Scaffolds prepared this way have a three-dimensional structure, a gradient pore size structure, high porosity, strong water absorption, suitable degradation rates and good compressive resistance.Besides, the good cell compatibility and low cytotoxicity of the scaffolds satisfy the requirements for osteochondral tissue engineering materials. Key words: Silk fibroin; Chitosan; Nano-hydroxyapatite; Osteochondral scaffold

Title Current Status and Future Challenges for Sustaining "Genuine" Japan-made Silk" by Sericulture/ Filature/ Silk Fabrication Collaborated Groups

In early twenty century， sericulture/filature was a leading industry to contribute to Japanese economy and recorded the largest export amounts for the country. However， after import liberalization in 60's and business recession from the first oil shock in 70's， the industry had been rapidly slowing down and shrank. Silk fabric production in Japan was also decreased mainly due to the imported silk fabric and garment. Currently， genuine Japan-made silk use is below one percent of the total silk product consumption. In order to maintain the Japan-made silk products， the collaborated groups among sericulture/filature/ silk fabrication industries were established by 2011. The objectives of this research are (1) to clarify the updated Japan-made silk consumption status and the industry structure through analysis of the performance of the collaborated groups， and (2) to understand current/future challenges for the groups. The research methods are the related data/report survey and interviews to the key group members. Main finished products of genuine Japan-made silk is for traditional “kimono” use. Major challenges for the collaborated groups is how to maintain domestic sericulture resources and strengthen the groups through integration and restructurings.

De Novo Design of Recombinant Spider Silk Proteins for Material Applications.

Spider silks are well known for their superior mechanical properties that are stronger and tougher than steel despite being assembled at close to ambient conditions and using water as the solvent. However, it is a significant challenge to utilize spider silks for practical applications due to their limited sources. Fortunately, genetic engineering techniques offer a promising approach to produce useable amounts of spider silk variants. Starting from these recombinant spider silk proteins, a series of experiments and simulations strategies are developed to improve the recombinant spider silk proteins (RSSP) material design and fabrication with the aim of biomimicking the structure-property-function relationships of spider silks. Accordingly, in this review, the authors first introduce the structure-property-function relationship of spider silks. Then, the recent progress in the genetic synthesis of RSSPs is discussed and their related multiscale self-assembly behaviors is summarized. Finally, the authors outline works utilizing multiscale modeling to assist RSSP material design.

Fabrication and characterization of electrospun laminin-functionalized silk fibroin/poly(ethylene oxide) nanofibrous scaffolds for peripheral nerve regeneration.

The peripheral nerve regeneration is still one of the major clinical problems, which has received a great deal of attention. In this study, the electrospun silk fibroin (SF)/poly(ethylene oxide) (PEO) nanofibrous scaffolds were fabricated and functionalized their surfaces with laminin (LN) without chemical linkers for potential use in the peripheral nerve tissue engineering. The morphology, surface chemistry, thermal behavior and wettability of the scaffolds were examined to evaluate their performance by means of scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and water contact angle (WCA) measurements, respectively. The proliferation and viability of Schwann cells onto the surfaces of SF/PEO nanofibrous scaffolds were investigated using SEM and thiazolyl blue (MTT) assay. The results showed an improvement of SF conformation and surface hydrophilicity of SF/PEO nanofibers after methanol and O2 plasma treatments. The immunostaining observation indicated a continuous coating of LN on the scaffolds. Improving the surface hydrophilicity and LN functionalization significantly increased the cell proliferation and this was more prominent after 5 days of culture time. In conclusion, the obtained results revealed that the electrospun LN-functionalized SF/PEO nanofibrous scaffold could be a promising candidate for peripheral nerve tissue regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1595-1604, 2018.

Biomimetic Coprecipitation of Silk Fibrin and Calcium Phosphate: Influence of Selenite Ions.

Large bone defect creates an urgent need for osteogenic biomaterials. However, bone nonunion and infection are choke points in the therapy of this disease. How to recruit the mesenchymal stem cells to defect sites and increase the cell viability are the critical processes. One effective method was the fabrication of biomimetic silk fibrin/selenium-doped hydroxyapatite (SF/HASe) material, which could create a niche for cell proliferation. So, the aim of the present study was to seek a facile route to prepare this biocomposites and investigate the osteogenic capability. Results showed that the biomimetic coprecipitation was a successful route to prepare SF/HASe biocomposites, which presented higher cell proliferation activity and better modulation of the selenite release during incubation in biological medium. Besides, the biocomposites exhibited weird and porous pot morphology. Such features could provide large surface area for the cells and proteins to attach. Silk fibrin, adhered onto the surface of hydroxyapatite (HA) crystals, plays a crucial impact on the release profile of selenite ions. The release behavior of the selenite ions exhibited stably slow release fashion. Therefore, it is feasible to employ SF/HASe biocomposites to repair bone defects and apply into the therapy of osteosarcoma postoperatively.

Fabrication of silk fibroin/eggshell nanofiber membranes for facemasks

We report our study on fabrication of soluble eggshell membrane (SESM) and silk fibroin (SF) nanofibers composite (SF/SESM) for facemasks by electrospinning. Biocompatibility of the SF and SESM, determined from hydrophilicity results, is exploited in SF/SESM nanocomposite for facemask application. The SF/SESM nanocomposites were prepared in different ratios of SF and SESM. The samples were characterized by scanning electron microscopy (SEM), FTIR and water droplet adsorption tests conducted via water contact angle (WCA) and water droplet diffusion. The results revealed that addition of SESM has insignificant effect on the electrospinnability of SF nanofibers in the studied ratios. The SEM results depicted regular morphology of the nanofibers except increase in nanofiber diameter with addition of SESM. The FTIR results confirmed respective peaks of SF and SESM in SF/SESM nanocomposite. WCA of the nanofibers decreased with addition of SESM such that for SF/SESM30, 30 % SESM, it reduced to 0 ° from 101 ° for pure SF nanofibers. The research results demonstrate SF/SESM30 nanocomposite as optimum ratio of SF and SESM for facemasks and other biomedical applications.

Fabrication of silk fibroin/cellulose whiskers–chitosan composite porous scaffolds by layer-by-layer assembly for application in bone tissue engineering

Bone tissue engineering necessitates a three-dimensional porous scaffold design to closely mimic the in vivo physiological biomimetic microenvironment with good mechanical properties to support the adhesion and proliferation of osteoblasts. In this study, a silk fibroin/cellulose nanowhiskers–chitosan (SF/CNW–CS) composite scaffold with excellent mechanical properties and biological compatibility was prepared by layer-by-layer assembly of CNW and CS onto a porous SF scaffold fabricated by freeze-drying. The morphology, assembly construct, and mechanical properties of the SF/CNW–CS composite scaffold were characterized using different technical methods. The hierarchical lamellar structure was formed by assembly of CNW and CS onto the SF lamella. Increasing the number of CNW and CS assembly layers to 108 slightly decreased the porosity from 86 to 78 % and simultaneously changed the compressive stress–strain curves from soft to hard tissue-like properties with an increase in compressive modulus from 2.5 to 12.5 MPa. Human MG-63 osteosarcoma cells were further cultured on the SF/CNW–CS scaffold to evaluate their suitability for bone tissue engineering. The results indicated that the SF/CNW–CS composite scaffold supported cell proliferation and promoted the levels of biomineralization-relevant alkaline phosphatase activity and osteocalcin expression over those for a porous SF scaffold. Taken together, our results indicate that the porous SF/CNW–CS composite material will be a promising tissue engineering scaffold for bone generation and implantation.

Novel fabrication of fluorescent silk utilized in biotechnological and medical applications

Novel fabrication of fluorescent silk utilized in biotechnological and medical applications

Cross-linked silk sericin–gelatin 2D and 3D matrices for prospective tissue engineering applications

Graphical abstract representing the isolation, fabrication and characterization of silk sericin/gelatin blended matrices for intended biological application.

Methods and Applications of Multilayer Silk Fibroin Laminates Based on Spatially Controlled Welding in Protein Films

Recent use of biopolymers as interface materials between planar, inorganic electronics and biological tissues has required the adaptation of micro‐ and nanofabrication techniques for use with these nontraditional materials. In this work, a method which builds on this principle for spatial control of adhesion in multilayer silk fibroin laminates is investigated. This is accomplished through the addition of a spatially patterned amorphous silk adhesive layer in between the films to be adhered, before thermally processing them with heat (120 °C) and pressure (80 Psi) according to established procedures. A one‐step method for rapid, high‐throughput fabrication is demonstrated, which establishes a strong (1100 kPa) bond between the layers independent of the initial processing conditions of the films. The adhesive layers can be patterned using existing silk fabrication techniques, allowing for the assembly of complex geometries including bilayers and microbubbles. Additionally, the utility of this method is demonstrated for potential applications in drug delivery and transient electronics. This approach provides a versatile method for construction of complex multilayer structures in silk, which with future work may ultimately improve the utility of this material as a bridge between high technology and the biomedical sciences.

Novel fabrication of fluorescent silk utilized in biotechnological and medical applications

Silk fibroin (SF) is a natural polymer widely used and studied for diverse applications in the biomedical field. Recently, genetically modified silks, particularly fluorescent SF fibers, were reported to have been produced from transgenic silkworms. However, they are currently limited to textile manufacturing. To expand the use of transgenic silkworms for biomedical applications, a solution form of fluorescent SF needed to be developed. Here, we describe a novel method of preparing a fluorescent SF solution and demonstrate long-term fluorescent function up to one year after subcutaneous insertion. We also show that fluorescent SF labeled p53 antibodies clearly identify HeLa cells, indicating the applicability of fluorescent SF to cancer detection and bio-imaging. Furthermore, we demonstrate the intraoperative use of fluorescent SF in an animal model to detect a small esophageal perforation (0.5 mm). This study suggests how fluorescent SF biomaterials can be applied in biotechnology and clinical medicine.

Fabrication and characterization of silk fibroin/chitosan/Nano γ-alumina composite scaffolds for tissue engineering applications

A series of silk fibroin/chitosan/Nano γ-alumina composite scaffolds have been prepared using the lyophilization technique for tissue engineering. These were then characterized using SEM, XRD, EDX, FTIR and TGA.

Green fabrication of porous silk fibroin/graphene oxide hybrid scaffolds for bone tissue engineering

The porous SF/GO scaffolds with moderate GO content could promote the proliferation of osteoblasts.

Fabrication and characterization of curcumin-loaded silk fibroin/P(LLA-CL) nanofibrous scaffold

Curcumin exhibited excellent properties including antioxidant, antiinflammatory, antiviral, antibacterial, antifungal, anticancer, and anticoagulant activities. In this study, curcumin was incorporated into silk fibroin (SF)/poly(L-lactic acid-co-e-caprolactone) (P(LLA-CL)) nanofibrous scaffolds via electrospinning, and changes brought about by raising the curcumin content were observed: SEM images showed that the average nanofibrous diameter decreased at the beginning and then increased, and the nanofibers became uniform; FTIR showed that the conformation of SF transforming from random coil form to β-sheet structure had not been induced, while SF conformation converted to β-sheet after being treated with 75% ethanol vapor; XRD results confirmed that the crystal structure of (P(LLA-CL)) had been destroyed; The mechanical test illustrated that nanofibrous scaffolds still maintained good mechanical properties. Further, curcumin-loaded nanofibrous scaffolds were evaluated for drug release, antioxidant and antimicrobial activities in vitro. The results showed that curcumin presented a sustained release behavior from nanofibrous scaffolds and maintained its free radical scavenging ability, and such scaffolds could effectively inhibit S. aureus growth (> 95%). Thus, curcumin-loaded SF/P(LLA-CL) nanofibrous scaffolds might be potential candidates for wound dressing and tissue engineering scaffolds.