Fabrication and characterization of 3-dimensional PLGA nanofiber/microfiber composite scaffolds

Novel three-dimensional (3-D) nano-/microfibrous poly(lactic-co-glycolic acid) (PLGA) scaffolds were fabricated by hybrid electrospinning, involving a combination of solution electrospinning and melt electrospinning. The scaffolds consisted of a randomly oriented structure of PLGA microfibers (average fiber diameter = 28 μm) and PLGA nanofibers (average fiber diameter = 530 nm). From mercury porosimetry, the PLGA nano-/microfiber (10/90) scaffolds were found to have similar pore parameters to the PLGA microfiber scaffolds. PLGA nano-/microfibrous scaffolds were examined and compared with the PLGA microfiber scaffolds in terms of the attachment, spreading and infiltration of normal human epidermal keratinocytes (NHEK) and fibroblasts (NHEF). The cell attachment and spreading of both cell types were several times higher in the nano-/microfiber composite scaffolds than in the microfibrous scaffolds without nanofibers. This shows that the presence of nanofibers enhanced the attachment and spreading of the cells on the nano-/microfiber composite scaffolds. Moreover, the nanofibers helped the cells infiltrate easily into the scaffolds. Overall, this novel nano-/microfiber structures has great potential for the 3-D organization and guidance of cells provided for tissue engineering.     

Synthesis and characterization of carbon nanofiber/alumina composite by extrusion casting

A macroscopic carbon nanofiber (CNF)/alumina composite was synthesized by extrusion casting. Its textural and mechanical properties, crystallinity, surface acidity and thermal stability were investigated using N₂ physisorption, scanning electron microscopy, temperature programmed desorption of NH₃ (NH₃-TPD), X-ray diffraction and thermal gravimetric (TG) analysis. It was shown that the CNFs and alumina were evenly and intimately blended in the composite which displayed a lateral crushing strength greater than 100 N/cm. The composite had a mesoporous structure, possessing a surface area greater than 320 m²/g and a narrow pore size distribution. NH₃-TPD results demonstrated that, compared to those on commercial alumina, the total number of acid sites on the composite (related to the total amount of desorbed NH₃) was significantly increased while the number of strong acid sites (related to the amount of desorbed NH₃ between 400 and 500 °C) was distinctly decreased. TG analysis revealed that the composite was stable up to 600 °C in air or 900 °C in an inert atmosphere.     

海藻酸钠/羟基磷灰石一体化复合支架的制备

采用高碘酸钠对海藻酸钠(SA)进行氧化得到氧化海藻酸钠(OSA),以丁二酸酐对壳聚糖(SC)进行接枝改性得到N–琥珀酰壳聚糖(NSC),并与OSA发生Schiff碱反应生成水凝胶。采用水热合成法制备了微米级、纳米级羟基磷灰石并进行相应表征,并与OSA、SA制备复合水凝胶。利用静电纺丝技术制备了聚ε–己内酯/聚乙二醇细胞分隔膜并表征其形貌特征。采用乳化剂交联法,制备了SA竖直贯通多孔支架并研究了SA浓度、复合纳米羟基磷灰石对支架的影响。通过模块化构建,制备出多层一体化组织工程支架,将各组分材料与人皮肤成纤维细胞共培养以考察支架的生物相容性,采用吖啶橙荧光染色法观察细胞生长情况,细胞增殖定量检测采用CCK–8表征。     

Thermal stability of polypropylene/carbon nanofiber composite

Thermal stability of polypropylene and carbon nanofibre composite system has been studied using Thermogravimetric Analysis, Limited Oxygen Index (LOI), Flammability, Calorimetry, and Oxidation Induction Time techniques. Definite improvement in thermo‐oxidative stability of the composite system has been observed. Improvement in LOI and a distinct change in the burning characteristics suggest a reduction in potential fire hazards. The nanocomposite system will have enhanced anti‐ageing characteristics and require more stringent conditions for the initiation of burning and the ultimate impact of burning will be less. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3574–3578, 2006     

PVA/Au纳米复合纤维的制备及表征

以聚乙烯醇(PVA)为还原剂和保护剂,采用PVA还原氯金酸(HAuCl4)制备纳米金(Au),一步法制备PVA/Au溶液,通过静电纺丝制备了PVA/Au纳米复合纤维.利用紫外可见光谱仪、透明电镜和扫描电镜对PVA/Au纳米复合纤维进行了表征.结果表明:随着HAuCl4浓度的增加,Au纳米粒子的粒径逐渐增大;HAuCl4...     

Superoleophobic and conductive carbon nanofiber/fluoropolymer composite films

A solution-based, large-area coating procedure is developed to produce conductive polymer composite films consisting of hollow-core carbon nanofibers (CNFs) and a fluoroacrylic co-polymer available as a water-based dispersion. CNFs (100 nm dia., length ～130 μm) were dispersed by sonication in a formic acid/acetone co-solvent system, which enabled colloidal stability and direct blending of the CNFs and aqueous fluoroacrylic dispersions in the absence of surfactants. The dispersions were sprayed on smooth and microtextured surfaces, thus forming conformal coatings after drying. Nanostructured composite films of different degrees of oil and water repellency were fabricated by varying the concentration of CNFs. The effect of substrate texture and CNF content on oil/water repellency was studied. Water and oil static contact angles (CAs) ranged from 98° to 164° and from 61° to 164°, respectively. Some coatings with the highest water/oil CAs displayed self-cleaning behavior (droplet roll-off angles <10°). Inherent conductivity of the composite films ranged from 63 to 940 S/m at CNF concentrations from 10 to 60 wt.%, respectively. Replacement of the long CNFs with shorter solid-core carbon nanowhiskers (150 nm dia., length 6–8 μm) produced stable fluoropolymer–nanowhisker dispersions, which were ink-jetted to generate hydrophobic, conductive, printed line patterns with a feature size ～100 μm.     

High conductivity electrospun carbon/graphene composite nanofiber yarns

Polyacrylonitrile/graphene (PAN/GP) composite nanofiber filaments were spun continuously by a homemade eight‐needle electrospinning device with an auxiliary electrode, and then, yarns were obtained by plying and successive twisting. Subsequently, the composite yarns were stabilized at 250–280°C for 1–2 h and then carbonized at 800–1100°C for 1–3 h. The diameter of yarns significantly decreased by over 60% after carbonization and the structure became more compact. The optimum stabilization conditions were at 270°C with holding for 1.5 h. The addition of GP at a low mass fraction (<1%) promoted the formation of ladder‐like structures and ordered graphitic structures during stabilization and carbonization. It seems there were defects in the pristine CNF, and the addition of GP reduced the defects. The conductivity of the composite CNF yarn sharply increased with the increase of GP content to 1%, and then decreased. The maximum value was 66.44 ± 13.16 S/cm at 1100°C held for 3 h. The mechanical properties for composite CNF yarns were performed. The maximum stress and modulus were 59.49 MPa and 14.63 GPa, respectively. POLYM. ENG. SCI., 58:903–912, 2018. © 2017 Society of Plastics Engineers     

3D printing of bioactive macro/microporous continuous carbon fibre reinforced hydroxyapatite composite scaffolds with synchronously enhanced strength and toughness

Continuous carbon fibre (CF) reinforced HA (CF/HA) composite scaffolds were prepared using a self-designed and manufactured 3D printer. The optimised design of nozzle structure and the tailored viscoelastic property of HA inks ensured compound extrusion of monofilament and multifilament CF with HA rod. The composite scaffolds designed using the CAD programme and sintered via a suitable process exhibited a hierarchical macro/microporous structure and contained approximately 50% HA and 50% β-TCP. The continuous CF synchronously enhanced the strength and toughness of the scaffolds. The compressive strengths of 1CF/HA and 5CF/HA were 11.4 ± 1.7 MPa and 16.3 ± 2.6 MPa, respectively, which were approximately double and triple compared with that of HA scaffolds. The fracture toughness of 1CF/HA was approximately double that of HA scaffolds and close to that of cortical bone. In vitro and in vivo studies demonstrated that 1CF/HA also had apatite formation capability and adequate bone regeneration capacity.     

Synthesis,characterization and bioactivity investigation of bioglass/hydroxyapatite composite

Bioactive glass of the type CaO–P₂O₅–SiO₂ was obtained by the sol–gel processing method. The obtained material was characterized by X-ray powder diffraction (XRD). Composite samples of hydroxyapatite with synthesized bioglass were prepared at 1000 °C and characterized by XRD, Fourier transform infrared spectroscopy (FTIR), and surface electron microscopy (SEM). The bioactivity was examined in vitro with respect to the ability of hydroxyapatite layer to form on the surface as a result of contact with simulated body fluid (SBF). XRD, FTIR and SEM studies were conducted before and after contact of the material with SBF. It could be detected that the bioglass was crystallized partly. Furthermore, silicated hydroxyapatite may have formed due to the diffusion of silicate groups to the apatite phase and these may have substituted for the phosphate groups. It can be concluded from SEM and FTIR results that apatite phase formed after 14 days in SBF.     

Development of composite tissue scaffolds containing naturally sourced mircoporous hydroxyapatite

The aims of this work were to investigate the conversion of a marine alga into hydroxyapatite (HA), and furthermore to design a composite bone tissue engineering scaffold comprising the synthesised HA within a porous bioresorbable polymer. The marine alga, Phymatolithon calcareum, which exhibits a calcium carbonate honeycomb structure, with a natural architecture of interconnecting permeable pores (microporosity 4–11 μm), provided the initial raw material for this study. The objective was to convert the alga into hydroxyapatite while maintaining its porous morphology using a sequential pyrolysis and chemical synthesis processes. Semi-quantitative XRD analysis of the post-hydrothermal material (pyrolised at 700–750 °C), indicated that the calcium phosphate (CaP) ceramic most likely consisted of a calcium carbonate macroporous lattice, with hydroxyapatite crystals on the surface of the macropores. Cell visibility (cytotoxicity) investigations of osteogenic cells were conducted on the CaP ceramic (i.e., the material post-hydrothermal analysis) which was found to be non-cytotoxic and displayed good biocompatibility when seeded with MG63 cells. Furthermore, a hot press scaffold fabrication technique was developed to produce a composite scaffold of CaP (derived from the marine alga) in a polycaprolactone (PCL) matrix. A salt leaching technique was further explored to introduce macroporosity to the structure (50–200 μm). Analysis indicated that the scaffold contained both micro/macroporosity and mechanical strength, considered necessary for bone tissue engineering applications.     

Fabrication and characterization of vapor grown carbon nanofiber/epoxy magnetic nanocomposites

Co₃O₄ nanoparticle‐decorated vapor‐grown carbon nanofiber (VGCNF) hybrid materials were successfully synthesized and served as nanofillers for preparing magnetic epoxy (EP) nanocomposites. The Co₃O₄‐decorated VGCNF (Co₃O₄‐VGCNF) and Co₃O₄‐VGCNF/EP nanocomposites were systematically and explicitly investigated by combined analytical techniques. The composition and phase structure of Co₃O₄‐VGCNF hybrid materials were characterized by Fourier transform infrared spectroscopy and X‐ray diffraction analyses. The morphology of Co₃O₄ was investigated using field‐emission scanning electronic microscopy (FE‐SEM). Results revealed the presence of Co₃O₄ nanoparticles firmly immobilized on VGCNF sidewalls. The tensile mechanical, thermomechanical, and magnetic properties of Co₃O₄‐VGCNF/EP nanocomposites were also investigated in detail. Results indicated that the tensile strength of Co₃O₄‐VGCNF/EP nanocomposites (filler = 0.5 wt%) improved by 44.6% compared with that of raw VGCNF/EP nanocomposites (filler = 0.5 wt%). Magnetization measurements revealed that Co₃O₄‐VGCNF/EP nanocomposites exhibited ferromagnetic behavior, and the saturation magnetization and coercivity of the nanocomposites with 2 wt% of Co₃O₄‐VGCNF were 0.055 emu g⁻¹ and 0.75 kOe, respectively. POLYM. COMPOS., 37:1728–1734, 2016. © 2014 Society of Plastics Engineers     

纳米炭纤维含量对其酚醛复合材料性能影响

采用纳米炭纤维对酚醛树脂改性,通过力学性能、烧蚀性能测试以及电镜和X-射线光电子能谱(XPS)分析研究了纳米炭纤维含量对炭/酚醛树脂基复合材料性能的影响。结果表明,当纳米炭纤维质量分数为15%时,其改性复合材料的层间剪切强度最大,达到31.17 MPa,氧乙炔线烧蚀率最小,为0.020 mm/s。分析了其改性机理,指出纳米炭纤维在树脂中的分散均匀程度是获得理想复合材料性能的关键。     

Silver-functionalized carbon nanofiber composite electrodes for ibuprofen detection

ABSTRACT: The aim of this study is to prepare and characterize two types of silver-functionalized carbon nanofiber (CNF) composite electrodes, i.e., silver-decorated CNF-epoxy and silver-modified natural zeolite-CNF-epoxy composite electrodes suitable for ibuprofen detection in aqueous solution. Ag carbon nanotube composite electrode exhibited the best electroanalytical parameters through applying preconcentration/differential-pulsed voltammetry scheme.     

Preparation and characterization of hydroxyapatite/chitosan–gelatin network composite

A novel composite composed of hydroxyapatite (HA) and a network formed via cocrosslinking of chitosan and gelatin with glutaraldehyde was developed. Two preparation methods are described in detail. A porous material, with similar organic–inorganic constituents to that of natural bone, was made by a unique sol–gel method. The formation of the network in the presence of HA was characterized using IR analysis. The morphology of the composites was also examined using SEM. In addition, XRD was applied to estimate the change in the component crystal. The results indicate that the presence of HA does not retard the formation of the chitosan/gelatin network. On the other hand, the polymer matrix has hardly any influence on the high crystallinity of HA. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2929–2938, 2000     

One-pot synthesis of graphene/hydroxyapatite nanorod composite for tissue engineering

This paper presents a convenient one-pot hydrothermal strategy for the synthesis of graphene nanosheet (GNS)/hydroxyapatite (HA) nanorod composites (GNS/HA). Characterization of GNS/HA nanorod composites denote that rod-like HA, which has an average length of 55 nm and diameter of 13 nm, anchors on both sides of GNS. Introducing graphene can effectively improve the hardness and Young’s modulus of HA. The synthesized GNS/HA nanorod composite containing 40 wt.% HA shows higher osseointegration ability with surrounding tissues, better biocompatibility, and more superior bone cellular proliferation induction than pristine graphene oxide and HA do. The biocompatibility of GNS/HA nanorod composite makes it a promising candidate for bone regeneration and implantation.     

Biomimetic growth of hydroxyapatite on super water-soluble carbon nanotube-protein hybrid nanofibers

We report here on a facile strategy for the creation of super water-soluble carbon nanotube (CNT)-protein hybrid nanofibers. Toluene-soluble CNTs were first synthesized by noncovalent functionalizing CNTs with a bifunctional linker, Z-glycine N-succinimidyl ester (Z-Gly-OSu), and then water-soluble CNT-protein hybrid nanofibers were created by phase-transferring the Z-Gly-OSu-functionalized CNTs from the toluene phase to protein aqueous solution. CNT-fibronectin (CNT-FN) and CNT-hemoglobin (CNT-HGB) hybrid nanofibers were successfully prepared in this work. Raman and XPS spectra confirmed the successful functionalization of CNTs with Z-Gly-OSu. TEM results indicated the formation of CNT-protein hybrid nanofibers. Biomimetic mineralization was conducted on the CNT-FN hybrid nanofibers and nanofiber film to explore the effects of protein and CNTs on the formation of hydroxyapatite (HA) crystals. SEM, Raman spectra, and TEM results indicated that the FN molecules promote the nucleation of crystalline nuclei and the CNT templates control the orientation of nuclei and the crystal growth of HA to form flake-like HA crystals.     

Microarchitectural and mechanical characterization of chitosan/hydroxyapatite/demineralized bone matrix composite scaffold

Porous degradable scaffolds are used extensively in bone tissue engineering. As well as material type, the architectural and mechanical characterizations of scaffolds are important to facilitate cell and tissue growth. Matrices composed of hydroxyapatite (HA), chitosan (CS) and demineralized bone matrix (DBM) may create an appropriate environment for the regeneration of bones. In this study, CS/HA/DBM scaffolds with sufficient structural integrity and high interconnected porosity were produced using different combinations of CS, HA and DBM. Both mechanical and biological properties of porous scaffolds were determined by local microarchitecture whose parameters were quantified based on micro computed tomography (Micro-CT) analysis. Within porosity range of 48–65%, the ranges of average compressive modulus and ultimate strength of the scaffolds were 3 ± 1–6 ± 1 kPa and 11 ± 2–24 ± 2 kPa, respectively. With the increase of HA concentration at the equal weight of DBM, the average trabecular thickness and trabecular separation increased and bone surface/volume ratio decreased, resulting in higher volume fraction and lower total porosity. In vitro, MC3T3-E1 preosteoblast cells were used to investigate cell attachment, spreading and proliferation on the scaffolds via hematoxyline and eosin (HE), scanning electron microscopy (SEM) and MTS assay. The results showed that MC3T3-E1 cells adhered to the surface of composite scaffolds, cell number increased with culture time. Cell viability increased with the HA particles decreased, changed little with the DBM increased. Consideration of the microarchitectural and mechanical characterization and biocompatibility of the scaffolds, 3:3:1.5 and 3:5:1.5 groups were believed to be the best in our study.