Blend films based on silk fibroin/hyaluronic acid

Protein and polysaccharide was the most important extracellular matrix in dermal tissue. In this study, Silk fibroin (SF) / hyaluronic acid (HA) blend films mimicking the dermal tissue components were prepared and investigated. The results indicated that HA and SF has a good miscibility, HA interfered with SF to form crystal structure. By using EDC as cross-linker, effective cross-linking function on SF and HA macromolecules was reacted, the water solubility of the blend films decreased obviously after being cross-linked by EDC. The existence of EDC could promote SF to form Silk I structure. L929 cells were seeded on these blend films and showed normal attachment morphology. Cell-matrix interactions established by newly formed extracellular matrix were observed after 5 days in culture. The MTT assay showed that cell proliferation on the SF/HA blend films were enhanced significantly compared with that on the SF and HA films. These new 2D SF/HA blend films provided a favorable microenvironment for the proliferation of L929 cells and hold a potential for dermal tissue regeneration.     

Antibacterial properties and color fastness of silk fabric dyed with turmeric extract

The use of non-toxic and eco-friendly natural dyes on textiles has received much attention due to the increased environmental awareness in order to avoid some hazardous synthetic dyes. In the present study, an eco-friendly approach was developed to impart color and antibacterial properties to silk fabrics dyed with turmeric extract as a non-toxic natural colorant. The natural colorant was extracted from Curcuma Longa rhizome. Copper sulfate, ferrous sulfate and potassium aluminium sulfate were applied in a pre-metallization process as mordanting agents. Antibacterial properties of treated fabrics were evaluated against common pathogenic bacteria, Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). The effects of dye concentration and mordant types on the obtained color hues, antibacterial efficiency and color fastness of the fabrics were investigated. The results indicated that mordanted and dyed fabrics possessed desirable antibacterial properties. Complete antibacterial activity of the treated fabrics was obtained with 3 %owf (on weight of the fabric) copper sulfate. It was also shown that increasing the dye concentration could lead to a more efficient antibacterial activity on the mordanted dyed fabrics. An optimum level of the antibacterial activity was observed in the sample treated with 30 %owf of turmeric. Furthermore, the results of CIE L*, a*, b* values, FTIR, washing, light and rubbing fastnesses of the dyed fabrics were reported. The mordanted dyed silk fabrics exhibited desirable color fastness properties. These studies proved a direct relationship between the degree of antibacterial activity of the fabrics treated with turmeric and the metals ion concentration.     

Metal ion adsorbability of electrospun wool keratose/silk fibroin blend nanofiber mats

In this study, electrospun wool keratose (WK)/silk fibroin (SF) blend nanofiber was prepared and evaluated as a heavy metal ion adsorbent which can be used in water purification field. The WK, which was a soluble fraction of oxidized wool keratin fiber, was blended with SF in formic acid. The electrospinnability was greatly improved with an increase of SF content. The structure and properties of WK/SF blend nanofibers were investigated by SEM, FTIR, DMTA and tensile test. Among various WK/SF blend ratios, 50/50 blend nanofiber showed an excellent mechanical property. It might be due to some physical interaction between SF and WK molecules although FTIR result did not show any evidence of molecular miscibility. As a result of metal ion adsorption test, WK/SF blend nanofiber mats exhibited high Cu²⁺ adsorption capacity compared with ordinary wool sliver at pH 8.5. It might be due to large specific surface area of nanofiber mat as well as numerous functional groups of WK. Consequently, the WK/SF blend nanofiber mats can be a promising candidate as metal ion adsorption filter.     

Antibacterial blend films of cellulose and chitosan prepared from binary ionic liquid system

A new hybrid ionic liquids solvent, 1-allyl-3-methylimidazolium chloride (AMIMCl) and glycine hydrochloride (Gly·HCl) was utilized to dissolve chitosan and fabricate chitosan/cellulose (Cs/Ce) blend films with chitosan proportion varying from 2 to 35 wt.% through solution casting method. FTIR, XRD, TG, SEM and EA were used to evaluate the prepared composites. Besides, the mechanical property and antibacterial activity were also analyzed. The shifting of the characteristic peaks of -NH and C=O for chitosan, similar crystal pattern with low intensity diffraction peaks at 2θ of around 20°, superior thermal stability (increased T_onset) with chitosan ratio below 10 wt.% in the composites suggested that the interactions via hydrogen bonds formed between chitosan and cellulose. Besides, the elemental analysis showed that the actual N% contents from the chitosan in the blend films were roughly equivalent to the theoretical value though the inevitable residue of ionic liquids. Furthermore, the blends not only presented compact structure but also processed high bacterial reduction to E. coli and S. aureus at pH 6.3, which indicated that the Cs/Ce blend films prepared via the Gly·HCl/AMIMCl dissolution method were suitable for production of degradable antibacterial materials.     

Preparation and characterization of Ceftazidime loaded electrospun silk fibroin/gelatin mat for wound dressing

Fabrication of Ceftazidime (CTZ) loaded silk fibroin/gelatin (SF/GT) nanofibers (NFs) without the loss of structure and bioactivity of CTZ was demonstrated by electrospinning method. The structure, morphology and mechanical properties of the electrospun SF/GT nanofibrous mats were characterized using FT-IR, SEM and DSC. The drug release profile of different electrospun fibers was analyzed using spectrophotometric method, and also diffusion method was applied to assess the antibacterial effect of NFs. Cell viability was evaluated by MTT assay. The results show that the average diameter of drug loaded NFs at the optimum polymer to drug feeding ratio (10:1) was 276.55±35.8 nm, while increasing the feeding ratio to 1:1 increases the average diameter to 825.02±70.3 nm. FT-IR of drug loaded NFs was revealed that CTZ was successfully encapsulated into NFs while viability study approved cytocompatibility of SF/GT NFs. CTZ was released from NFs during 6 h, and formation of inhibition zone in diffusion test demonstrated the antibacterial effect of drug loaded NFs. Altogether, the CTZ loaded SF/GT NFs can improve the drug effectiveness particularly in the prevention of post-surgical adhesions and infections for wound dressing.     

Structure and properties of silk fibroin modified cotton

In this research, a novel cotton fiber with a silk fibroin (SF) coating was prepared by the oxidation of a cotton thread with sodium periodate and subsequent treatment in a solution of silk fibroin. The structures of both the oxidized cotton samples and the SF modified cotton samples were investigated by Fourier transform infrared (FT-IR) in combination with X-ray photoelectron spectroscopy (XPS) analysis. Other performances such as surface morphology and breaking strength were also studied. The results indicated that the weight of the oxidized cotton samples increased during SF treatment, while that of the un-oxidized cotton (pure cotton) samples reduced after SF treatment. Compared with the pure cotton samples, the oxidized cotton clearly showed a characteristic absorption band at 1730 cm⁻¹ due to the stretching vibration of the C=O double bond of the aldehyde group. After being treated with the SF solution, the oxidized cotton fiber showed a weakened characteristic absorption band at 1730 cm⁻¹ and a new absorption band at round 1540 cm⁻¹, suggesting the formation of C-N bond between aldehyde groups in the oxidized cotton and primary amines in the silk fibroin. The results were also confirmed by XPS analysis. Compared with the oxidized cotton samples, the SF treated cottons had relatively smooth surfaces, similar breaking strength, and the improved wrinkle recovery angles. The results in this research suggest that cotton based materials with protein coating can be achieved without using any other crosslinking agents by the method introduced.     

Pentacene crystal formation on the surface of silk fibroin films

Silk fibroin (SF) has attracted interest as a gate dielectric due to its electrical insulation and high mobility in pentacene based organic thin film transistors (OTFTs). In this research, the surface energy of SF is controlled by water annealing, ethanol, and methanol solution treatments in order to study the effect of pentacene morphology on SF thin films with various treatments. For different crystallization methods, the crystal structures and surface energies of SF were investigated in detail by FT-IR and contact angle. Methanol treated SF thin film has a lower surface energy than the other two thin films. Topologies of pentacene on the SF thin films with various surface energies were obtained by atomic force microscopy (AFM). The AFM results showed that the smallest grain size of pentacene was that on methanol treated SF thin film which demonstrated that methanol treated SF thin film can be a proper candidate for a gate dielectric in OTFTs.     

Preparation of electrospun silk fibroin/Cellulose Acetate blend nanofibers and their applications to heavy metal ions adsorption

Silk fibroin (SF)/Cellulose Acetate (CA) blend nanofibrous membranes were prepared by electrospinning and their heavy metal absorbabilities were examined in an aqueous solution after ethanol treatment. The electrospun nanofibrous membranes were comprised of randomly oriented ultrafine fibers of 100–600 nm diameters. As a result of field emission electron microscope (FEEM), the anti-felting properties of the blend nanofibrous membranes were markedly improved after treatment with 100 % ethanol when SF was blended with CA. Metal ion adsorption test was performed with Cu²⁺ as a model heavy metal ion in a stock solution. The SF/CA blend nanofiber membranes showed higher affinity for Cu²⁺ in an aqueous solution than pure SF and pure CA nanofiber membranes. Especially, the blend nanofibrous membranes with 20 % content of CA had an exceptional performance for the adsorption of Cu²⁺, and the maximum milligrams per gram of Cu²⁺ adsorbed reached 22.8 mg/g. This indicated that SF and CA had synergetic effect. Furthermore, the parameters affecting the metal ions adsorption, such as running time and initial concentration of Cu²⁺, had been investigated. The results showed that the adsorption of the Cu²⁺ sharply increased during the first 60 min, the amount of metal ions adsorbed increased rapidly as the initial concentration increased and then slope of the increase decreased as the concentration further increased. This study provides the relatively comprehensive data for the SF/CA blend nanofibrous membranes application to the removal of heavy metal ion in wastewater.     

Miscibility, structural characteristics, and thermal behavior of wet spun regenerated silk fibroin/nylon 6 blend filaments

In this study, the regenerated silk fibroin (SF)/nylon 6 blend filaments were fabricated by the wet spinning and miscibility, structural characteristics, and thermal behavior of blend filaments were elucidated. The XRD results implied that the amount of crystalline region of each polymer did not change linearly with the blend ratio suggesting that there are some changes in the miscibility depending on the mixing ratio. The SEM observation revealed that the miscibility of blend decreased with an increase of nylon 6 resulting in a severe phase separation in 50/50 SF/nylon 6 filament. The miscibility governed the thermal behavior of blend filaments. The melting point of nylon 6 remained constant until 50 % nylon 6 content, whereas the melting point depression appeared in 30 % nylon 6 implying miscibility. Interestingly, the thermal decomposition of the nylon 6 component was accelerated by the presence of SF and the acceleration action of SF became stronger as the miscibility increased.     

Relationships between antithrombogenicity and surface free energy of regenerated silk fibroin films

Silk fibroin (SF) was dissolved in calcium chloride/ethanol/water mixture (1/2/8 in mole ratio) at 70°C for 4 h. The dissolved silk fibroin was regenerated by casting the dialyzed solution into the films. The films were treated with 50% aqueous solution of methanol for different times, and their antithrombogenicity was evaluated byin vitro andin vivo tests.In vivo blood tests were made by a method of peripheral vein indwelling suture. It was found that the silk fibroin had a good anti-thrombogenicity and an absorbability even though the polymer showed foreign body reaction. Finally, the blood compatibilty of silk fibroin films which were subjected to structural change by the methanol treatment, was examined in connection with their interfacial surface energy, and a correlation between these properties was found to be present.     

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.     

Antibacterial Bombyx Mori silk fabric modified with reactive chitosan quaternary ammonium salt and its laundering durability

A new fiber-reactive chitosan derivative was synthesized in two steps from a chitosan of low molecular weight. First, a water-soluble chitosan derivative, N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (short for HTCC), was prepared by reacting chitosan with 2,3-epoxypropyltrimethylammonium chloride. Second, HTCC was further modified by reacting with N-(hydroxymethyl)-acrylamide to prepare a fiber-reactive chitosan derivative, O-methyl acrylamide quaternary ammonium salt of chitosan (short for NMA-HTCC), which can form covalent bonds with silk fiber under alkaline conditions. The chemical structure of NMA-HTCC was characterized by Fourier transform infrared spectrum (FTIR) and nuclear magnetic resonance (NMR). The substitution degree of HTCC and the double-bond content of NMA-HTCC were tested. Then NMA-HTCC was used for antibacterial finishing of Bombyx Mori silk fabric. The results showed that silk fabric treated with NMA-HTCC had a significantly improved antibacterial activity to Staphylococcus aureus and Escherichia coli, and the antibacterial activity of silk fabric finished by NMA-HTCC was much better than that finished by chitosan and HTCC. Bombyx Mori silk fabric modified with NMA-HTCC demonstrated excellent durable antibacterial activity, even after 50 repeated launderings, the bacterial reduction rate of silk fabric maintained over 95 %.     

Cellulose nanofiber-reinforced silk fibroin composite film with high transparency

We successfully prepared optically transparent silk fibroin-cellulose nanofiber (CN) composite films from solvent casting using a stable CN suspension in an aqueous silk fibroin solution. The transmittance of the silk fibroin composite films was observed by a UV-visible spectrophotometer. The secondary structural change of the silk fibroin caused by the incorporation of CNs was characterized using Fourier transform infrared spectroscopy. A tensile test was carried out to investigate the mechanical properties. The results showed that the composite film exhibited visible-light transmittance of 75 %, and its mechanical strength and Young’s modulus were increased by 44 % and 35 %, respectively, as compared to a neat silk fibroin film.     

EDC/NHS crosslinked electrospun regenerated tussah silk fibroin nanofiber mats

The tussah silk fibroin (TSF) nanofibers with 611 nm diameters were prepared by electrospinning with the solvent hexafluoroisopropanol (HFIP). And then, the TSF nanofibers were crosslinked by 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide/N-Hydroxysuccinimide (EDC/NHS) crosslinking agent. The morphology and microstructure of the crosslinked TSF nanofibers were characterized by scanning electron microscopy (SEM), Fourier transforms infrared analysis (FTIR), X-ray diffraction, Instron electronic strength tester, and cell culture. After treatment with EDC/NHS crosslinking agent, the TSF nanofibers swelled and its average diameter increased from 611 to 841 nm. FTIR and X-ray diffraction results demonstrated that random coil, ??-helix, and ??-sheet co-existed in the TSF nanofiber mats, but the content of ??-sheet increased from 25.26 to 45.34 %, and the random coil content decreased from 32.47 to 24.94 %. Compared with the electrospun pure TSF nanofiber mats, the crosslinked TSF nanofiber mats exhibited a lower breaking tenacity and initial modulus, which were 5.51 MPa and 9.86 MPa, respectively. At the same time, the extension at break of the crosslinked TSF nanofiber achieved 109.38 %. In cell culture evaluation, the crosslinked TSF nanofibers were found to support cell adhesion and spreading fibroblast L373 and bone marrow mesenchymal stem cells (BMSCs), which had potential utility in a range of tissue engineering.     

Structural and physical properties ofAntheraea pernyi silk fibroin fiber treated with I2-KI aqueous solution

Silk fibroin (SF) fiber from theAntheraea pernyi silkworm was treated with a 1.23 N iodine-potassium iodide (I₂-KI) aqueous solution, and the structure and physical properties were investigated to clarify the effects of the iodine treatment. The noticeably high weight gain value of SF fiber, about 25 wt% was attributed to the absorption of polyiodide ions in the form of I₃ ^? and I₅ ^?. Fourier transform infrared spectroscopy and X-ray diffraction measurements suggested that polyiodide ions mainly entered the amorphous region. In addition, a new sharp reflection on the meridional direction, corresponding to a period of 7.0 Å, was observed and indicated the possibility of the formation of mesophase structure ofβ-conformation chains. Dynamic viscoelastic measurements showed that the damping tanδ peak at 270°C gradually shifted to lower temperature in the iodinated SF fibers, suggesting an enhancement of the molecular motion of the fibroin chains induced by the presence of polyiodide ions. With heating above 254 °C, the iodine component introduced intermolecular cross-linking of SF, and the melt flow of the sample was inhibited. The thermal decomposition stability of fibroin molecules was greatly enhanced by iodine treatment.     

Mechanism of silk fibroin scaffolds with oriented multichannels and its cytocompatibility

As a biomaterial, besides excellent biocompatibility and biodegradability, suitable macropores and pores structure should be provided to guide cell extension and migration. In present study, the silk fibroin (SF) scaffold with uniaxial channels was prepared by directional temperature field freezing technique. The average pore diameter, pore density and porosity of the scaffold with oriented channels are ～128.7 µm, ～158 mm^?2 and ～91.4 %, respectively. By controlling of the temperature gradient direction, the oriented multichannels of the scaffolds were formed in longitudinal easily. In process of the scaffolds fabrication, the directional growth of ice crystal could shear and draft to the silk fibroin molecule segments, which resulted in the new crystal nucleus formation in new zone and increase of β-sheet components in the scaffolds. In vitro, L929 cells were seeded on the scaffolds with oriented channels to evaluate the effect on cell behavior. Cell viability, adhesion and morphology were determined by methyl thiazolyl tetrazolium, confocal microscope and scanning electron microscope. The results showed that the cells anchored on the oriented channels, spread along the direction of the channels and hold a higher viability on the scaffolds with oriented channels. These new oriented multichannel scaffold could guide the adhesion and proliferation of L929 cells, which hold a potential in tissue engineering.     

Surface modification of silk fibroin nanofibrous mat with dextran for wound dressing

In this study, we examined the effects of a dextran-modified silk fibroin nanofibrous mat (D-SFNM) on wound healing. To increase the hydrophilicity of silk fibroin (SF), the SF nanofibrous mat (SFNM) was modified with oxidized dextran. The D-SFNM absorbed water faster than the SFNM, and the swelling ratio was increased by approximately 80 % compared with the SFNM. An in vitro cell (NIH3T3) test revealed that fewer cells attached to the D-SFNM than the SFNM, but the proliferation of cells was not significantly affected by the presence of dextran. An in vivo wound healing test with mice indicated that the D-SFNM resulted in a good wound recovery effect similar to a commercial wound dressing material. The increased hydrophilicity of the D-SFNM might balance the moist environment at the wound site, which improves the wound healing compared with the SFNM.     

Dyeing properties and antimicrobial activity of silk fabric with extract of unripe Citrus Unshiu fruits

This study was carried out to optimize dyeing conditions of unripe Citrus Unshiu extract on silk fabric and to evaluate antimicrobial activity of the dyed fabric for its potential use as a functional natural dye. Unripe fruits of Citrus Unshiu in Jeju Island, Korea, extracted in 80 % Ethanol solution to final solid dye powder were dyed on silk fabric under a variety of conditions such as dye bath concentrations, temperature, and dyeing duration together with mordanting. Dyeing fastness properties to washing, rubbing, perspiration, and light were tested and the antimicrobial activities of the dyed fabric against Staphylococcus aureus and Klebsiella pneumoniae were investigated quantitatively. As results, the fabric showed the maximum dye uptake (K/S) under the conditions of 80 °C for temperature, 30 min for duration, and 600 % (o.w.f.) for dye concentration. Both pre- and post-mordanting seemed not to be effective on increasing K/S values of the dyed silk fabrics under the optimum dyeing conditions. Fastness ratings to washing, rubbing, and perspiration were all very good (4–5 grades) for both 300 and 600 % dyed silk fabrics. Excellent antimicrobial activities over 99 % reduction rate against two both bacteria were exhibited for all of dyed fabrics undergone more than 300 % of dye concentration. From these results, it was concluded that the dye concentration of 300 % of unripe Citrus Unshiu could be employed to produce antimicrobial silk fabric. Furthermore, to get more saturated shades on the fabric by the citrus, higher dye concentration such as 600 % was available as well.     

Antimicrobial electrospun silk fibroin mats with silver nanoparticles for wound dressing application

In this report, silk fibroin (SF) mats coated with silver nanoparticles (AgNPs) were manufactured as a prototypic wound dressing and evaluated for antimicrobial properties. SF was extracted from cocoons of Thai silkworms Bombyx mori (variant Nangnoi Si Sa Ket) and fabricated into nonwoven mats by electrospinning. In a one-step synthesis method, colloidal AgNPs were prepared from silver nitrate by gamma irradiation and inspected by transmission electron microscopy. Using the in vitro disc diffusion and growth-inhibition assays, AgNP-coated SF mats effectively inhibited the growth of Staphyllococus aureus and Pseudomonas aeruginosa when the coating solution containing colloidal AgNPs was 4 mM, or equivalent to 50.4 ng/cm² of adsorbed AgNPs. Based on these results, the AgNP-coated SF mats can potentially be used as antimicrobial wound dressings.     

Preparation and characterization of bacterial cellulose/hydroxypropyl chitosan blend as-spun fibers

In the work, N-methylmorpholine-N-oxide monohydrate (NMMO·H₂O) was used as a solvent to solve bacterial cellulose (BC) and hydroxypropyl chitosan (HPCS) together, and regenerated bacterial cellulose (RBC)/HPCS blend as-spun fibers were prepared by blending BC with HPCS via wet-spinning in the Lyocell process. Structure and properties of the blend as-spun fibers were characterized by different techniques, together with the antibacterial activity of the blend as-spun fibers against Staphylococcus aureus. Results revealed that HPCS was mixed with BC very well. The blend as-spun fibers showed a rough and folded surface morphology and an interior pore structure on the cross-section. Compared with pure RBC as-spun fibers, the blend as-spun fibers had lower degree of crystallinity and thermal stability. Although extension at break of the blend as-spun fibers was lower than the pure RBC as-spun fibers, their tensile strength and modulus had been enhanced obviously. The blend as-spun fibers were also found to exhibit excellent antibacterial activities against S. aureus.