Hybrid biomimetic electrospun fibrous mats derived from poly(ε‐caprolactone) and silk fibroin protein for wound dressing application

To achieve excellent biofunctionality of Bombyx mori silk fibroin (SF), we explored a novel hybridization method to combine the unique properties of SF with poly(ε‐caprolactone) (PCL) electrospun fibers. The hybrid electrospun fibers demonstrate excellent hydrophilicity and biocompatibility that are important to tissue engineering applications. The biomimetic fibrous structure was fabricated by conventional electrospinning of PCL. The individual surfaces of PCL electrospun fibers were coated with silk fibroin protein using a lyophilization technique. The SF coating layers were durable which were further developed by surface modification with fibronectin to improve their biological function. The hybrid electrospun fibers show excellent support for normal human dermal fibroblast (NHDF) cells adhesion and proliferation than neat PCL fibers, while the surface‐modified hybrid electrospun fibers show significantly enhanced proliferation of NHDF cells on their surface. This study indicates the new opportunity of fabrication technique that can construct a biomimetic fibrous structure while the original function as a biomaterial remained existing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41653.     

离子液体对丝素蛋白溶解性能的影响

合成了一系列碱性离子液体,其中离子液体1-丁基-3-甲基咪唑乙酸盐([Bmim]AC)对丝素蛋白具有良好的溶解性能。考察了丝素蛋白在该离子液体中的溶解特性及在离子液体中的溶解温度和溶解时间,结果表明,在75℃下,溶解840 min,该离子液体对丝素蛋白的溶解能力达到15%(质量分数)。XRD和FTIR分析表明,再生丝素蛋白的构象以α-螺旋为主,丝素蛋白在溶解过程中没有发生衍生化。因此,[Bmim]AC离子液体是丝素蛋白的优良溶剂。     

Rapid formation of flexible silk fibroin gel‐like films

Flexible silk fibroin gel‐like films with microporous morphology were prepared from B. mori silk fibroin fibers directly solubilized in formic acid/CaCl₂ solvent. These films were characterized by several analysis techniques to determine the structure and properties of films. The pore size of gel‐like films can be adjusted through SF concentration and Ca ions concentration. The controllable pore size in gel‐like films was grew from 3–5 μm to 100 μm under the increase of fibroin concentration from 1.0 wt % to 8.0 wt %. At the same time, the water content of silk fibroin gel‐like film decreased from 83.5 ± 3.4% to 68.2 ± 2.6%. With increasing Ca ions contents from 2.0 wt % to 10.0 wt % in dissolution process, the pore size and water content of silk fibroin gel‐like films grew larger, especially its water content values reached 86.2 ± 4.0% at 10.0 wt % Ca ions concentration. At wet condition, the gel‐like film with β‐sheet structure showed higher breaking stress (4.26 ± 0.31 MPa) and elongation (45.45 ± 15.79%) at 8.0 wt % concentration. With the preparation method, the membrane is hydrophilic and the pore size is adjustable, which contributes to high toughness and favorable cell growth environment, suggesting that these silk fibroin gel‐like films can be a potential candidate scaffold for biomedical applications, such as wound dressing, facial mask, contact lenses, etc. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41842.     

Effects of superfine silk protein powders on mechanical properties of wet‐spun polyurethane fibers

Mechanical measurements were employed to investigate the effects of three types of superfine silk protein powder on tensile strength, elongation, and elasticity of wet‐spun Pellethane^® 2363‐80AE polyurethane (PU) fiber. These superfine silk protein powders included undegummed silk (with both native silk fibroin and sericin, water insoluble), native silk fibroin (with native silk fibroin only, water insoluble), and regenerated silk fibroin (with regenerated silk fibroin only, water soluble) in powder form. Experimental data derived from the mechanical measurements illustrated that the miscibility between the PU and regenerated silk fibroin were superior to that between PU and the other two silk proteins. This may be attributed to the similar chemical structure and microphase separation of PU and regenerated silk fibroin with lower molecular weight than native silk fibroin. This preliminary work may provide some information for biomimetic processing of silk‐inspired PU biofibers, which combine elasticity of synthetic PU with biofunction of natural silk fibroin for special biomedical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Chitosan‐finished Antheraea mylitta silk fibroin nonwoven composite films for wound dressing

In this study, we aimed to produce nonwoven wound‐dressing films made of Antheraea mylitta (tasar) silk fibroin by a solution‐casting method. These nonwoven films were finished with chitosan solutions of different concentrations ranging from 0.75 to 2% w/v with a pad–dry method to fabricate nonwoven composite films. Chitosan‐finished tasar fibroin nonwoven composite films (CMTFFs) showed higher mechanical and dynamic mechanical properties as compared to nonwoven tasar fibroin. The physical, structural, and thermal properties of the films were investigated. The hemocompatibility, cytocompatibility, and biodegradation tests showed that the CMTFF was a promising material for use as a wound dressing. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44341.     

Immobilization of glucose oxidase on nonwoven fabrics with bombyx mori silk fibroin gel

The enzyme glucose oxidase (GOD) was immobilized on the nonwoven fabrics, which have excellent properties in diffusivity of substrates, mechanical strength, and handling, with Bombyx mori silk fibroin gel. The nonwoven fabrics of silk fibroin, viscose rayon, poly-ethyleneterephthalate, 6-nylon, and polypropylene with activated surface by fluoline treatment were used. The stabilities of GOD to heat or pH changes were much improved by the immobilization as well as the case of the GOD immobilized in the silk fibroin membrane. Among nonwoven fabrics, silk fibroin was the most excellent support material for the immobilization of GOD although all nonwoven fabrics used here are able to be used as the support materials. The increase of the sensitivity was observed when the glucose sensor was made with the GOD immobilized on nonwoven silk fabrics as four times compared with the case of the GOD immobilized in the silk fibroin membrane.     

Investigation on the morphological and mechanical properties of (polyamide 6)/(poly[styrene‐co‐acrylonitrile])/(poly[styrene‐b‐{ethylene‐co‐butylene}‐b‐styrene]) ternary blends

In this work, ternary polymer blends based on (polyamide 6)/(poly[styrene‐co‐acrylonitrile])/(poly[styrene‐b‐{ethylene‐co‐butylene}‐b‐styrene]) (SEBS) triblock copolymer and a varying concentration of the reactive (maleic anhydride)‐grafted SEBS were prepared by using a melt‐blending process. The effects of the material parameters (composition of ternary blends and SEBS/[{maleic anhydride}‐grafted SEBS] concentration ratio) and blending sequence on the morphological and mechanical properties of ternary blends were studied. Taguchi experimental design methodology was employed to design the experiments and select the material and processing parameters for the optimized mechanical properties. Tensile properties (Young's modulus and yield stress) and impact strength were considered as the response variables. It was demonstrated that there is a meaningful relationship between the composition of blends, processing parameters, observed phase structure, and obtained mechanical properties. The mechanical tests showed that the highest impact strength was achieved as the dispersion of the rubbery phase achieved an optimum size of about 1 μm. J. VINYL ADDIT. TECHNOL., 23:329–337, 2017. © 2015 Society of Plastics Engineers     

Study on the properties of nano‐TiO2 particles modified silk fibroin porous films

Using the freeze‐drying method, Nano‐TiO₂/silk fibroin porous films were synthesized with different ratios of TiO₂ to silk fibroin solution. Through scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), tensile strain, and water‐solubility tests, the structures and properties of these porous films were characterized. The SEM results indicated that the pores of the nano‐TiO₂/silk fibroin porous films were uniformly distributed by the freeze‐drying method. The XRD analysis indicated that the formation of nano‐TiO₂ particles might induce a conformational transition of silk fibroin from the typical Silk I to the typical Silk II structure partly with an increase in the crystallinity of the porous films. Compared with the pure silk fibroin porous films, the mechanical properties of nano‐TiO₂/silk fibroin porous films were improved, and its heat transition temperature was also enhanced; however, the water‐solubility of this material was diminished. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study on secondary structural transition of nano‐TiO2 modified silk fibroin composite films by two‐dimensional Raman correlation spectroscopy and solid‐state 13C‐NMR spectroscopy

By a sol–gel processing, the nano‐TiO₂/silk fibroin (SF) composite films were prepared. One‐dimensional (1D) Raman, two‐dimensional (2D) correlation Raman spectroscopy, and ¹³C cross‐polarization magic‐angle‐spinning nuclear magnetic resonance (¹³C CP‐MAS NMR) were used to characterize the structural evolution of SF as the nano‐TiO₂ content increased from 0 to 0.4 wt%. The experimental data demonstrated that the secondary structures in the pure SF film and nano‐TiO₂/silk fibroin (SF) composite films were random coil, α‐helix and β‐sheet structures. The nano‐TiO₂ particles formed in the SF films might induce partial structural transitions from random coil and Silk I (α‐helix) to Silk II (β‐sheet). The transition identified by 2D‐Raman correlation spectra was the following order: silk I‐like structure, silk I (α‐helical structure), Silk II‐like structure, and Silk II (β‐sheet structure). POLYM. COMPOS., 36:121–127, 2015. © 2014 Society of Plastics Engineers     

Recycling Chiral Imidazolidin‐4‐one Catalyst for Asymmetric Diels–Alder Reactions: Screening of Various Ionic Liquids

Various imidazolium ionic liquids such as [Bmim]PF₆, [Bmim]SbF₆, [Bmim]OTf and [Bmim]BF₄ were screened for recycling an organic catalyst [(5S)‐5‐benzyl‐2,2,3‐trimethylimidazolidin‐4‐one ( 1 )] for asymmetric Diels–Alder reactions. Good yields and enantioselectivies (up to 85% yield and 93% ee) were obtained from reactions in [Bmim]PF₆ or [Bmim]SbF₆. However, reactions in [Bmim]OTf or [Bmim]BF₄ gave racemic products in low yields. Isolation of the products by simple extraction using diethyl ether allowed recycling of the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities.     

Synthesis and characterization of spinning poly(acrylonitrile‐co‐silk fibroin peptide)s

A novel spinning acrylic polymer containing silk protein was synthesized by copolymerization of acrylonitrile (AN) and silk fibroin peptide (SFP) modified by acryloyl chloride (AC) with vinyl groups. From results of the examination to the chemical compositions, we established that the modified SFP is more reactive than AN in the copolymerization. The intrinsic viscosity values of these copolymers showed that the copolymers have good spinnability, which were synthesized under the condition of adding a trace of metal ions into the synthesizing solvent. These copolymers exhibited good thermal property. The fiber based on the poly(acrylonitrile‐co‐silk fibroin peptide) was prepared and characterized by SEM, FTIR measurement of its shell and core flakes, and moisture absorption. The fiber exhibited a smooth surface and could be assumed to have excellent adhesive property between SFP and PAN. Furthermore, these fibers showed a core–shell structure and excellent moisture absorption. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1540–1547, 2004     

Production of silk fibroin nanoparticles using ionic liquids and high‐power ultrasounds

Biopolymeric nanoparticles have attracted great research interest in the last few years due to their multiple applications. This article describes how high‐power ultrasounds are capable of enhancing the dissolution process of silk proteins in ionic liquids (ILs) and how silk fibroin nanoparticles (SFNs) can be obtained directly from the silk/ionic liquid solution (SIL) by rapid desolvation in polar organic solvents. The silk fibroin integrity is highly preserved during the dissolution process, as confirmed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) of the SIL. These regenerated SFNs are insoluble in water and other common organic solvents and are indistinguishable from the classical SFNs with respect to their diameter (180 ± 5 nm), Zeta potential (?25 ± 3 mV), high degree of β‐sheet and low cytotoxicity. Large amounts of silk can be turned into biomaterials directly from the SIL solution for use in a wide range of applications, while the ILs can be recovered from the coagulant solution under reduced pressure and reused without loss of their solvent properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41702.     

Preparation and characterization of poly[(butylene succinate)‐co‐(butylene adipate)]/carbon nanotube‐coated silk fiber composites

Biodegradable composites consisting of aliphatic polyesters (poly[(butylenes succinate)‐co‐(butylenes adipate)] (PBSA)) and Bombyx mori silk fibers coated with carbon nanotubes (CNTs) were prepared by melt compression molding. The mechanical properties of PBSA were enhanced by the incorporation of a small amount (3 wt%) of CNT‐coated silk fibers, while allowing its potential biodegradability to be retained, which could make these composites good candidates for commodity materials such as general‐purpose plastics. This improvement is attributed to the interactions between PBSA and CNT‐coated silk fibers in the composites. The average interfacial shear strength of the composites consisting of CNT‐coated silk fibers and PBSA matrix was 1.7 MPa, as measured by the microbond droplet test, while that of composites consisting of pure silk fibers and PBSA was only 1.1 MPa. The morphology of the CNT‐coated silk fiber‐reinforced composites was observed using scanning electron microscopy. Copyright © 2007 Society of Chemical Industry     

Mechanical and thermal properties of poly(butylene succinate)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) biodegradable blends

Biodegradable polymer blends of poly(butylene succinate) (PBS) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) were prepared with different compositions. The mechanical properties of the blends were studied through tensile testing and dynamic mechanical thermal analysis. The dependence of the elastic modulus and strength data on the blend composition was modeled on the basis of the equivalent box model. The fitting parameters indicated complete immiscibility between PBS and PHBV and a moderate adhesion level between them. The immiscibility of the parent phases was also evidenced by scanning electron observation of the prepared blends. The thermal properties of the blends were studied through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results showed an enhancement of the crystallization behavior of PBS after it was blended with PHBV, whereas the thermal stability of PBS was reduced in the blends, as shown by the TGA thermograms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42815.     

Fabrication of cellulose membrane with “imprinted morphology” and low crystallinity from spherulitic [Bmim]Cl

In the present study, regenerated cellulose membrane with “imprinted morphology” and low crystallinity was fabricated from the crystal cellulose/[Bmim]Cl solution. Spherulites of 1‐butyl‐3‐methilimidazolium chloride ([Bmim]Cl) and cellulose/[Bmim]Cl solution were observed using polarized optical microscopy under certain condition. The fabricated cellulose membranes presented some particular characteristics compared with the membrane prepared from traditional cellulose/[Bmim]Cl solution. All the fabricated membranes were characterized by optical microscope, Wide‐angle X‐ray diffraction (WAXD), thermo‐gravimetric analysis, and mechanical testing. The images showed that the resulting membranes prepared from crystal cellulose/[Bmim]Cl solution were “imprinted” with patterns which originated from the crystalline structure of [Bmim]Cl. The results of WAXD showed that the obtained cellulose membrane exhibited low diffraction peaks and crystallinity of approximately 24.57%. Furthermore, the low crystallinity led to the low mechanical property (27.5 MPa), thermal stability (315.4 °C), and high moisture regain (9.5%). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43798.     

Preparation and characterization of quartz‐fiber‐cloth‐reinforced,polymerization‐of‐monomer‐reactant‐type polyimide substrates with a high impact strength

A series of novel quartz‐fiber‐cloth‐reinforced polyimide substrates with low dielectric constants were successfully prepared. For this purpose, the A‐stage polyimide solution was first synthesized via a polymerization‐of‐monomer‐reactant procedure with 2,2′‐bis(trifluoromethyl)benzidine and 3,3′,4,4′‐oxydiphthalic anhydride as the monomers, and cis?5‐norbornene‐endo‐2,3‐dicarboxylic anhydride as the endcap. Then, an A‐stage polyimide solution (TOPI) was impregnated with quartz‐fiber cloth (QF) to afford the prepregs, which were thermally molded into the final substrate composites. The influence of the curing temperature and the resin content on the mechanical properties of the composite were examined. The composites exhibited a high glass‐transition temperature over 360°C, a low and steady dielectric constant below 3.2 at a test frequency of 1–12 GHz, and a volume resistance over 1.8 × 10¹⁷ Ω cm. Meanwhile, they also showed a high mechanical strength with flexural and impact strengths in ranges 845–881 MPa and 141–155 KJ/m², respectively. The excellent mechanical and thermal properties and good dielectric properties indicated that they are good candidates for integrated circuit packaging substrates. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42358.     

Influence of acetated‐based and bromo‐based ionic liquids treatment on wool dyeing with acid blue 7

Bromo‐based and acetated‐based ionic liquids (ILs), 1‐butyle‐3‐methylimidazolium bromo ([Bmim]Br), 1‐ethyl‐3‐mthylimidazolium bromo ([Emim]Br), 1‐butyle‐3‐methylimidazolium acetate ([Bmim]Ac), and 1‐ethyl‐3‐mthylimidazolium acetate ([Emim]Ac), were synthesized and employed for wool surface treatment. Scanning electron microscope results indicated that the wool surfaces treated with acetated‐based ILs were eroded more than those treated with bromo‐based ILs. Comparable studies showed that the wool samples treated with acetate‐based ILs, especially [Emim]Ac, had higher initial dyeing rate and equilibrium exhaustion than those with bromo‐based ILs. Along with treatment temperature and time increasing, acetate‐based ILs had more remarkable effects on mechanical and dyeing properties of the wool samples than bromo‐based ILs. The wool samples treated with [Emim]Ac at 60°C for 10 min had excellent low‐temperature dyeing properties. The color depth (K/S) investigations showed that the wool samples treated with acetate‐based ILs possessed darker color depth than those treated with the bromo‐based ILs. Color fastnesses of the wool samples treated with [Bmim]Br, [Emim]Br and [Bmim]Ac exhibited the same grades as the untreated sample, while wet color fastnesses of [Emim]Ac treated sample were slightly decreased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Biodegradable studies of poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone), poly(dioxanone), and poly(glycolide‐ε‐caprolactone) (Monocryl®) monofilaments

The aim of the study was to investigate the mechanical properties and biodegradability of poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone) [P(TMC‐ε‐CL)‐block‐PDO] in comparison with poly(p‐dioxanone) and poly(glycolide‐ε‐caprolactone) (Monocryl®) monofilaments in vivo and in vitro. P(TMC‐ε‐CL)‐block‐PDO copolymer and poly(p‐dioxanone) were prepared by using ring‐opening polymerization reaction. The monofilament fibers were obtained using conventional melt spun methods. The physicochemical and mechanical properties, such as viscosity, molecular weight, crystallinity, and knot security, were studied. Tensile strength, breaking strength retention, and surface morphology of P(TMC‐ε‐CL)‐block‐PDO, poly(p‐dioxanone), and Monocryl monofilament fibers were studied by immersion in phosphate‐buffered distilled water (pH 7.2) at 37°C and in vivo. The implantation studies of absorbable suture strands were performed in gluteal muscle of rats. The polymers, P(TMC‐ε‐CL)‐block‐PDO, poly(p‐dioxanone), and Monocryl, were semicrystalline and showed 27, 32, and 34% crystallinity, respectively. Those mechanical properties of P(TMC‐ε‐CL)‐block‐PDO were comparatively lower than other polymers. The biodegradability of poly(dioxanone) homopolymer is much slower compared with that of two copolymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 737–743, 2006     

Synthesis and properties of random copolymers of 2,2‐dimethyltrimethylene carbonate and ethylene carbonate catalyzed by lanthanide tris(2,6‐di‐tert‐butyl‐4‐methylphenolate)

Random copolymers of 2,2‐dimethyltrimethylene carbonate and ethylene carbonate (EC) were synthesized with lanthanide tris(2,6‐di‐tert‐butyl‐4‐methylphenolate)s [Ln(DBMP)₃; Ln = La, Nd, Sm, or Dy] as catalysts, among which La(DBMP)₃ showed the highest activity. Poly(2,2‐dimethyltrimethylene carbonate‐co‐ethylene carbonate)s [poly(DTC‐co‐EC)]s with high molecular weights were prepared at room temperature and characterized with ¹H‐NMR and size exclusion chromatography. The thermal behavior and crystalline properties of the poly(DTC‐co‐EC)s were analyzed with differential scanning calorimetry, thermogravimetric analysis, and X‐ray diffraction. The crystallinity and melting temperatures of the poly(DTC‐co‐EC)s both decreased with increasing EC content in the copolymers. The mechanical properties of these copolymers were also investigated with dynamic mechanical analysis and tensile strength measurements, which revealed that a reduction of the glass‐transition temperature and great enhancement of the tensile properties could be achieved with higher EC contents. These improvements in the thermal and mechanical properties indicate potential applications in biomedical research for novel polycarbonates. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rhodium Acetate Dimer Immobilized in 1‐Butyl‐3‐methylimidazolium Hexafluorophosphate Ionic Liquid: a Novel and Recyclable Catalytic System for the Cyclopropanation of Alkenes

Alkenes undergo smooth cyclopropanation with ethyl diazoacetate using a catalytic amount of rhodium acetate dimer, Rh₂(OAc)₄, immobilized in the air‐ and moisture‐stable 1‐butyl‐3‐methylimidazolium hexafluorophosphate ionic liquid, [bmim]PF₆, to afford cyclopropanecarboxylates in excellent yields with high trans‐selectivity. The recovery of the catalyst is facilitated by the hydrophobic nature of [bmim]PF₆. The recovered ionic liquid containing Rh₂(OAc)₄ can be reused for three to five subsequent runs with only a gradual decrease in activity.