Electrospun Fe3O4/PVP//Tb(BA)3phen/PVP magnetic–photoluminescent bifunctional bistrand aligned composite nanofibers bundles

Fe₃O₄/PVP//Tb(BA)₃phen/PVP magnetic–photoluminescent bifunctional bistrand aligned composite nanofibers bundles based on Fe₃O₄ nanoparticles (NPs) and terbium complex Tb(BA)₃phen (BA = benzoic acid) were fabricated by employing a parallel axial electrospinning setup and were characterized by X-ray diffraction, field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy, fluorescence spectroscopy, and vibrating sample magnetometer. It is found that Fe₃O₄ NPs were only dispersed into one strand of the bistrand aligned composite nanofibers bundles, but no nanoparticles in the other strand. And the average diameter of the individual strand fiber was 200 ± 25 nm. The bistrand aligned composite nanofibers bundles exhibit strong green emissions under the excitation of 275 nm ultraviolet light, and the ⁵ D ₄ → ⁷ F ₅ hypersensitive transition at 545 nm was the predominant emission peak of Tb³⁺ ions. The newly obtained bifunctional nanofibers bundles exhibit excellent magnetism and high fluorescence intensity and are expected to apply in biology cell separation, magnetic resonance imaging, drug deliver, and fluorescence immunoassays/imaging.     

An exploratory study on the efficacy of rat dedifferentiated fat cells (rDFATs) with a poly lactic-co-glycolic acid/hydroxylapatite (PLGA/HA) composite for bone formation in a rat calvarial defect model

In the last two decades, tissue-engineering approaches using scaffolds, growth factors, and cells, or their combination, have been developed for the regeneration of periodontal tissue and bone. The aim of this study was to examine the effects of rat dedifferentiated fat cells (rDFATs) with a poly lactic-co-glycolic acid/hydroxylapatite (PLGA/HA) composite on bone formation in rat calvarial defects. Twenty animals surgically received two calvarial defects (diameter, 5 mm) bilaterally in each parietal bone. The defects were treated by one of the following procedures: PLGA/HA+osteo-differentiated rDFATs implantation (PLGA/HA+rDFATs (OD)); PLGA/HA+rDFATs implantation (PLGA/HA+rDFATs); PLGA/HA implantation (PLGA/HA); no implantation as a control. The animals were euthanized at 8 weeks after the surgery for histological evaluation. The PLGA/HA composite was remarkably resorbed and the amounts of residual PLGA/HA were very slight at 8 weeks after the surgery. The PLGA/HA-implanted groups (PLGA/HA+rDFATs (OD), PLGA/HA+rDFATs and PLGA/HA) showed recovery of the original volume and contour of the defects. The newly formed bone area was significantly larger in the PLGA/HA group (42.10 ± 9.16 %) compared with the PLGA/HA+rDFATs (21.35 ± 13.49 %) and control (22.17 ± 13.08 %) groups (P < 0.05). The percentage of defect closure (DC) by new bone in the PLGA/HA+rDFATs (OD) group (83.16 ± 13.87 %) was significantly greater than that in the control group (40.61 ± 29.62 %) (P < 0.05). Furthermore, the PLGA/HA+rDFATs (OD) group showed the highest level of DC among all the groups. The present results suggest that the PLGA/HA composite is a promising scaffold and that PLGA/HA+DFATs (OD) may be effective for bone formation.     

Transport properties of electrodeposited copper telluride (Cu2Te) nanowires embedded in polycarbonate track-etch membrane

In this paper, electronic transport properties of electrodeposited copper telluride (Cu₂Te) nanowires at room temperature (303 K) embedded in polycarbonate track-etch membranes (Whatman, 6 μm thick, pores density of order 10⁸ pores/cm²) as template with pores of diameter 200, 100 and 50 nm have been reported. Scanning electron microscopy equipped with energy dispersive X-ray spectrometer and X-ray diffractometry (XRD) were used to characterize the morphology and structure of the nanowires. I–V measurements of copper telluride nanowires of different diameter have shown symmetric and ohmic behavior in the voltage range used in this experiment. The temperature (T) dependent electrical conductivity measurements over a temperature (T) range of 308–423 K reveal that the electrical conductivity increases with increasing temperature and decreases as the size of the nanowires reduces. The electrical conductivity (at T ≥ room temperature) was observed significantly higher in copper telluride nanowires of higher diameter compared to lower diameter which attributes to the size effect. The activation energies (E _a ) are found to be 2.34, 3.11 and 5.01 meV in low-temperature range of 308–340 K and 0.15, 0.28 and 0.57 meV in high-temperature range of 340–423 K for 200, 100 and 50 nm nanowires respectively. The temperature dependence of electrical resistance measurements has shown the nanowires have negative temperature coefficient of resistance (TCR).     

In-vitro anticancer and antimicrobial activities of PLGA/silver nanofiber composites prepared by electrospinning

In the present work, a series of 0, 1 and 7 wt% silver nano-particles (Ag NPs) incorporated poly lactic-co-glycolic acid (PLGA) nano-fibers were synthesized by the electrospinning process. The PLGA/Ag nano-fibers sheets were characterized using SEM, TEM and DSC analyses. The three synthesized PLGA/silver nano-fiber composites were screened for anticancer activity against liver cancer cell line using MTT and LDH assays. The anticancer activity of PLGA nano-fibers showed a remarkable improvement due to increasing the concentration of the Ag NPs. In addition to the given result, PLGA nano-fibers did not show any cytotoxic effect. However, PLGA nano-fibers that contain 1 % nano silver showed anticancer activity of 8.8 %, through increasing the concentration of the nano silver to 7 % onto PLGA nano-fibers, the anticancer activity was enhanced to a 67.6 %. Furthermore, the antibacterial activities of these three nano-fibers, against the five bacteria strains namely; E.coli o157:H7 ATCC 51659, Staphylococcus aureus ATCC 13565, Bacillus cereus EMCC 1080, Listeria monocytogenes EMCC 1875 and Salmonella typhimurium ATCC25566 using the disc diffusion method, were evaluated. Sample with an enhanced inhibitory effect was PLGA/Ag NPs (7 %) which inhibited all strains (inhibition zone diameter 10 mm); PLGA/Ag NPs (1 %) sample inhibited only one strain (B. cereus) with zone diameter 8 mm. The PLGA nano-fiber sample has not shown any antimicrobial activity. Based on the anticancer as well as the antimicrobial results in this study, it can be postulated that: PLGA nanofibers containing 7 % nano silver are suitable as anticancer- and antibiotic-drug delivery systems, as they will increase the anticancer as well as the antibiotic drug potency without cytotoxicity effect on the normal cells. These findings also suggest that Ag NPs, of the size (5–10 nm) evaluated in the present study, are appropriate for therapeutic application from a safety standpoint.     

Photoluminescence–electricity–magnetism trifunction simultaneously assembled into one flexible nanofiber

In order to develop new-typed multifunctional composite nanofibers, Eu(BA)₃phen/PANI/Fe₃O₄/PVP trifunctional composite nanofibers with photoluminescence, electricity and magnetism have been successfully fabricated via electrospinning technology. Polyvinyl pyrrolidone (PVP) is used as a matrix to construct composite nanofibers containing different amounts of Eu(BA)₃phen, polyaniline (PANI) and magnetite Fe₃O₄ nanoparticles (NPs). X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, fluorescence spectroscopy and Hall effect measurement system are used to characterize the morphology and properties of the obtained composite nanofibers. The results indicate that the trifunctional composite nanofibers possess excellent luminescent, electrical conductivity and magnetic properties. Fluorescence emission peaks of Eu³⁺ are observed in the Eu(BA)₃phen/PANI/Fe₃O₄/PVP photoluminescent-electrical-magnetism trifunctional composite nanofibers and assigned to the of ⁵D₀ → ⁷F₀ (580 nm), ⁵D₀ → ⁷F₁ (593 nm) of Eu³⁺, and the ⁵D₀ → ⁷F₂ hypersensitive transition at 615 nm is the predominant emission peak. The electrical conductivity reaches up to the order of 10^?3 S/cm. The luminescent intensity, electrical conductivity and saturation magnetization of the composite nanofibers can be tunable by adding various amounts of Eu(BA)₃phen, PANI and Fe₃O₄ NPs. The multifunctional composite nanofibers are expected to possess many potential applications in areas such as electromagnetic interference shielding, microwave absorption, molecular electronics and biomedicine.     

Polymer Nanofibers Incorporated with Silver Nanoparticles: Thermal Properties

In this study, photothermal techniques were used to investigate the thermal diffusivity, effusivity, and conductivity of samples based on polyvinylidene difluoride (PVDF) polymeric nanofibers incorporated with silver nanoparticles (Ag-NPs). Different amounts were investigated to analyze the thermal effect of Ag-NPs on the polymeric matrix. The Ag-NPs were synthesized by sol–gel and microwave-assisted methods, which have advantages over conventional synthesis methods. The composite of PVDF nanofibers and Ag-NPs was obtained by electrospinning technique while varying the processing parameters. The UV–Vis characteristic spectrum of the nanoparticles was obtained. The hydrodynamic radius of the Ag-NPs was about 16 nm, which was determined by a nanozetasizer. A ζ potential of about 0.03 mV was also measured in this system. This parameter is a measure of the magnitude of the repulsion or electrical attraction between particles and is one of the main measurements to determine the stability of nanoparticles. The morphologies were observed by scanning electron microscopy and showed cylindrical fibers with diameters ranging from 159 nm to 658 nm. Transmission electron microscopy was used to observe the incorporation and distribution of Ag-NPs in the PVDF nanofibers. The thermal effects of Ag-NPs on the polymeric matrix were determined from the thermal properties. The thermal conductivity increased from 0.12 W·m^?1·K^?1 to 0.34 W·m^?1·K^?1 when the Ag-NP amount was increased from 4 % to 12 % in the polymeric matrix.     

Bone induction by biomimetic PLGA copolymer loaded with a novel synthetic RADA16-P24 peptide in vivo

Bone morphogenetic protein-2 (BMP-2) is a key bone morphogenetic protein, and poly(lactic-co-glycolic acid) (PLGA) has been widely used as scaffold for clinical use to carry treatment protein. In the previous studies, we have synthesized BMP-2-related peptide (P24) and found its capacity of inducing bone regeneration. In this research, we have synthesized a new amphiphilic peptide Ac-RADA RADA RADA RADA S[PO4]KIPKASSVPTELSAISTLYLDDD-CONH2 (RADA16-P24) with an assembly peptide RADA16-Ion the P24 item of BMP2 to form divalent ion-induced gelatin. Two methods of physisorption and chemical cross-linking were used to bind RADA16-P24 onto the surface of the copolymer PLGA to synthesize RADA16-P24–PLGA, and its capacity of attaching bone marrow stromal cells (BMSCs) was evaluated in vitro and inducing ectopic bone formation was examined in vivo. In vitro our results demonstrated that RADA16-P24–PLGA copolymer prepared by physisorbing or prepared by chemical cross-linking had a peptide binding rate of (2.0180 ± 0.5296)% or (10.0820 ± 0.8405)% respectively (P < 0.05). In addition the BMSCs proliferated vigorously in the RADA16-P24–PLGA biomaterials. Significantly the percentage of BMSCs attached to RADA16-P24–PLGA composite prepared by chemical cross-linking and physisorbing were (71.4 ± 7.5) % or (46.7 ± 5.8) % (P < 0.05). The in vivo study showed that RADA16-P24–PLGA chemical cross-linking could better induce ectopic bone formation compared with RADA16-P24–PLGA physisorbing and PLGA. It is concluded that the PLGA copolymer is a good RADA16-P24 carrier. This novel RADA16-P24–PLGA composite has strong osteogenic capability.     

On the importance of the structure in the electrical conductivity of fishbone carbon nanofibers

Carbon nanofibers (CNFs) have a remarkable electrical conductivity resulting highly attractive for different applications such as composites or electronics due to their high quality/price ratio. Although it is known that their graphitic character provides a high conductivity, very little is known about the influence of the nanofibers structure on that property. In this study, CNFs characterized by different physical properties are prepared at diverse synthesis temperatures within a range (550–750 °C) in which significant structural and dimensional changes are accomplished and homogeneous nanofiber growth takes place. The electrical conductivity is determined on the powdery as-grown materials modifying the compaction degree by applying pressure. Because of a combination of structural features, the apparent electrical conductivity increases with synthesis temperature of CNFs, ranging from 50 S m^?1 for the worst conducting CNFs at a low compaction degree (25 % of solid volume fraction) to 3 × 10³ S m^?1 for the best conducting CNFs at a high compaction degree (60 % of solid volume fraction). Further analysis is carried out applying the percolation theory to analyze the experimental data and the results suggest that both the orientation of the graphenes and the filament diameter distribution play a determining role in the intrinsic electrical conductivity with values in the interval 1.5 × 10³ to 1.3 × 10⁴ S m^?1. These intrinsic values of electrical conductivity are found between one and two orders of magnitude higher than that of the powder, highlighting the also important effect of porosity.     

Characteristics of curcumin-loaded poly (lactic acid) nanofibers for wound healing

Curcumin (Cur) is a well-known extract of the root of Curcuma longa L. that has multi biological functions such as anti-oxidation, anti-inflammatory, anti-cancer, and wound healing properties. In the present study, poly (lactic acid) (PLA) nanofibers were used as a carrier for Cur because PLA nanofibers are biocompatible and have a high-specific surface area and high porosity, which can enhance the functional properties of Cur. The chemical and biological characteristics of Cur/PLA blended nanofibers containing varied amounts of Cur were examined. An increase from 0.125 to 6.250 wt% Cur in PLA caused a decrease in the diameters of the nanofibers from 971 ± 274 to 562 ± 177 nm. At Cur concentrations of <1.250 wt%, PLA and Cur showed good miscibility in the blended nanofibers, as shown by FTIR analysis and tensile tests. The inclusion of Cur in the blended nanofibers at concentration as low as 0.125 wt% promotes the attachment and proliferation of cells. The in vivo wound healing capability of Cur-loaded PLA nanofibers was assessed in a mouse model; treatment with Cur-loaded PLA nanofibers significantly increased the rate of wound closure (87 %) by day 7 compared with that of PLA nanofibers (58 %). The results of this study suggest that Cur-loaded nanofibers with appropriate Cur concentration are nontoxic and have potential as component of wound-healing patches.     

Effect of aluminum substitution on microstructure and magnetic properties of electrospun BaFe12O19 nanofibers

BaFe_12?x Al _x O₁₉ nanofibers (x = 0–2.0) with average diameter 110 nm have been prepared via the electrospinning and subsequent heat treatment at 1100 °C for 2 h. Individual BaFe₁₂O₁₉ nanofibers were composed of numerous nanocrystallites stacking alternatively along the long axis of fiber and the single crystallites on each nanofibers had random orientations. With increasing Al³⁺ ions substitution contents from 0 to 2.0, the diameter and morphology of nanofibers were almost no change. However, the lattice parameters decreased due to Fe³⁺ ions substituted by smaller Al³⁺ ions and the average grain size calculated by the Scherrer’s equation reduced from 47 to 42 nm. The crystallites possessed a hexagonal plate-like shape at x = 0 while they became rod-like with various Al³⁺ ions substitution. The X-ray diffraction patterns show that single-phase barium hexaferrite was formed when Al³⁺ ions substitution contents were less than and equal to 1.0, while other impurity phases were detected when they were more than 1.0. The chemical analysis shows that the element Al was all incorporated into the lattice of BaFe₁₂O₁₉ and evenly distributed throughout the BaFe_12?x Al _x O₁₉ nanofibers. The magnetic testing shows that the saturation magnetization (M _s) decreased obviously from 63.92 to 29.70 A m²/kg, while coercivity (H _c) increased significantly from 288.2 to 740.7 kA/m with increasing Al³⁺ ions substitution.     

Solution blown aligned carbon nanofiber yarn as supercapacitor electrode

Carbon materials with various microtextures and wide availabilities represent very attractive electrode materials for supercapacitors. In this paper, a modified solution blowing process, using a pair of parallel rods as collector, was reported to fabricate carbon nanofiber yarn (CNFY) with polyacrylonitrile (PAN) as precursor polymer. The morphology and structure of the nanofibers were investigated. The PAN precursor and carbon nanofibers were well-aligned and their average diameter was 280 nm and 187 nm, respectively. The performance of CNFY as supercapacitor electrode was evaluated. The CNFY possessed high conductivity of 608.7 Scm^?1 and mass specific capacitance of 70 Fg^?1 at the current density of 500 mAg^?1, and the reduction of capacitance is 29.14 % of the initial value at the current density range from 0.5 to 8 Ag^?1. The superior performance of the CNFY electrode was attributed to the well-aligned structure and high electrical conductivity which afforded the potential application as a novel electrode for supercapacitors.     

Influence of different sulfur sources on the phase formation of Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> (CZTS) nanoparticles (NPs)

Wurtzite (Wz) and kesterite (Ks) phases of Cu₂ZnSnS₄ (CZTS) nanoparticles (NPs) have been selectively synthesized via hot injection method using 1-octadecene (1-ODE) as solvent. The solvents, 1-dodecanethiol (1-DDT) and tert-dodecanethiol (t-DDT) were utilized to control the reactivity of metal precursors and to tune the desirable crystallographic phases. The phase purity of the as synthesized CZTS NPs was confirmed using X-ray diffraction results. TEM images indicate that the developed nanoparticles consist of a mixture of triangular shaped (height 20?±?3 nm, width 17?±?2 nm) and sphere shaped NPs (13.4?±?0.4 nm). These nanoparticles were formed due to the influence of thiols without any additional capping ligands. The band gap of as-synthesized CZTS NPs were calculated as 1.41 eV for wurtzite phase (Wz—1-DDT) and 1.47 eV for kesterite phase (Ks—t-DDT) from UV–Visible absorption results. CZTS thin films were prepared via spin coating and the electrical properties were analysed using Hall Effect measurements. Both the phases of CZTS films exhibit p-type conductivity. Wurtzite phase of CZTS has higher mobility (23.6 cm^?3) and carrier concentration (2.64?×?10¹⁷) compared to kesterite phase of CZTS films.     

Physical and electrical attributes of sintered Ag80–Al20 high temperature die attach material with different organic additives content

In this work, the primary focus was to establish a relationship between the post-sintered physical attributes of the high temperature Ag₈₀–Al₂₀ die attach material and its electrical performance. The post-sintered Ag₈₀–Al₂₀ die attach material depicted the formation of Ag₂Al and Ag₃Al compounds. The melting point and maximum operational temperature for the Ag₈₀–Al₂₀ die attach material was determined to be 518 ± 1 °C and approximately 400 °C respectively, whereby the maximum operational temperature was based on a homologue temperature ratio of 0.85. The die attach material also demonstrated good electrical properties, i.e., an electrical conductivity value of 1.005 × 10⁵ (ohm–cm)^?1, which is higher than or equal to that of most solder systems. By varying the nanoparticle versus organics content between 83.3 and 87.0 %, it was seen that the surface morphology of the die attach material changed and the root-mean-square roughness values reduced to 175.1 nm. A similar observation was seen as the sintering temperature increased between 100 and 380 °C. This reduction in surface roughness proved that there was grain growth and particle coalescence within the die attach material. This translated to a reduction in electrical resistivity. Die attach area and thickness simulations found that smaller and thinner die attach areas are preferred for the Ag₈₀–Al₂₀ die attach material, whereby the highest recorded electrical conductivity value was 1.006 × 10⁵ (ohm–cm)^?1 for an area of 0.2 × 0.2 cm² and thickness of 25.4 μm.     

Facile electrospinning fabrication and photoluminescence of LaOI:Tb3+ one-dimensional nanomaterials

LaOI:Tb³⁺ nanomaterials including nanofibers, nanobelts, and hollow nanofibers were successfully synthesized by electrospinning combined with a double-crucible iodination method using NH₄I as iodine source for the first time. X-ray diffractometry analysis revealed that LaOI:Tb³⁺ nanostructures were phase-pure tetragonal structure with space group of P4/nmm. Scanning electron microscopy analysis showed that the diameters of LaOI:Tb³⁺ nanofibers, hollow nanofibers and the width of nanobelts were respectively 199.5 ± 30, 376.05 ± 48 nm and 5.2 ± 1.3 μm under the 95 % confidence level. The thickness of the tubewall for hollow nanofibers was 40.5 nm and the thickness of LaOI:Tb³⁺ nanobelts was 154 nm. Photoluminescence (PL) study demonstrated that the LaOI:Tb³⁺ nanomaterials exhibited the emission peaks located at 485, 544, 583 and 625 nm, which were ascribed to ⁵D₃ → ⁷F₁, ₆, ⁵D₄ → ⁷F₅, ⁵D₄ → ⁷F₄ and ⁵D₄ → ⁷F₃ of energy level transitions of Tb³⁺, respectively. The PL intensity was strongly affected by the Tb³⁺-doping concentration, and the optimum quenching concentration was 9 %. The luminescence intensity of LaOI:Tb³⁺ nanofibers was obviously stronger than that of LaOI:Tb³⁺ hollow nanofibers and nanobelts under the same measuring conditions. Commission Internationale de L’Eclairage (CIE) analysis demonstrated that the luminescence color of LaOI:9 % Tb³⁺ nanostructures were located in the green region in CIE chromaticity coordinates diagram. The possible formation mechanisms of LaOI:Tb³⁺ one dimensional nanomaterials were also proposed.     

Effect of aluminum oxide doping on the structural,electrical, and optical properties of zinc oxide (AOZO) nanofibers synthesized by electrospinning

Zinc oxide nanofibers doped with aluminum oxide were prepared by sol–gel processing and electrospinning techniques using polyvinylpyrrolidone (PVP), zinc acetate and aluminum acetate as precursors. The resulting nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, and current–voltage (I–V) properties. The nanofibers had diameters in the range of 60–150 nm. The incorporation of aluminum oxide resulted in a decrease in the crystallite sizes of the zinc oxide nanofibers. Aluminum oxide doped zinc oxide (AOZO) nanofibers exhibited lower bandgap energies compared to undoped zinc oxide nanofibers. However, as the aluminum content (Al/(Al + Zn) × 100%) was increased from 1.70 at.% to 3.20 at.% in the electrospinning solution, the bandgap energy increased resulting in lower conductivity. The electrical conductivity of the AOZO samples was found to depend on the amount of aluminum dopant in the matrix as reflected in the changes in oxidation state elucidated from XPS data. Electrospinning was found to be a productive, simple, and easy method for tuning the bandgap energy and conductivity of zinc oxide semiconducting nanofibers.     

Novel electro-conductive nanocomposites based on electrospun PLGA/CNT for biomedical applications

Electro-conductive nanocomposites have several applications in biomedical field. Development of a biocompatible electro-conductive polymeric materials is therefore of prime importance. In this study, electro-conductive nanofibrous mats of PLGA/CNT were fabricated through different methods including blend electrospinning, simultaneous PLGA electrospinning and CNT electrospraying and ultrasound-induced adsorption of CNTs on the electrospun PLGA nanofibers. The morphology and diameter of fibers were characterized by SEM and TEM, showing the lowest average diameters of 477?±?136?nm for PLGA/MWCNT blend nanocomposites. MWCNT-sprayed PLGA specimens showed significant lower water contact angle (83°), electrical resistance (3.0?×?10⁴?Ω) and higher mechanical properties (UTS: 5.50?±?0.46?MPa) compared to the untreated PLGA scaffolds. Also, results of PC12 cell study demonstrated highest viability percentage on the MWCNT-sprayed PLGA nanofibers. We propose that the conductive nanocomposites have capability to use as tool for the neural regeneration and biosensors.

Open image in new window

     

Stimulation of healing within a rabbit calvarial defect by a PCL/PLGA scaffold blended with TCP using solid freeform fabrication technology

The purpose of this study was to investigate the healing capacity within an 8-mm rabbit calvarial defect using a polycaprolactone (PCL)/poly(lactic-co-glycolic acid) (PLGA) scaffold blended with tri-calcium phosphate (TCP) that was constructed using solid freeform fabrication (SFF) technology. The PCL/PLGA/TCP scaffold showed a 37?% higher compressive strength and rougher surface than the PCL/PLGA scaffold. In animal experiments, new bone formation was analyzed using microcomputed tomography (micro-CT) and histological and histometric analyses. The PCL/PLGA/TCP groups had significantly greater neo-tissue areas as compared with the control groups at 4 and 8 weeks (P?<?0.05). The PCL/PLGA/TCP group had significantly greater bone density as compared with the control and PCL/PLGA groups at 4 and 8 weeks (P?<?0.005). The results of this study suggest that the PCL/PLGA/TCP scaffold fabricated using SFF technology is useful for recovering and enhancing new bone formation in bony defects in rabbits.     

Fabrication,characterization and in vitro drug release behavior of electrospun PLGA/chitosan nanofibrous scaffold

In this study both aligned and randomly oriented poly(d,l-lactide-co-glycolide) (PLGA)/chitosan nanofibrous scaffold have been prepared by electrospinning. The ratio of PLGA to chitosan was adjusted to get smooth nanofiber surface. Morphological characterization using scanning electron microscopy showed that the aligned nanofiber diameter distribution obtained by electrospinning of polymer blend increased with the increase of chitosan content which was similar to that of randomly oriented nanofibers. The release characteristic of model drug fenbufen (FBF) from the FBF-loaded aligned and randomly oriented PLGA and PLGA/chitosan nanofibrous scaffolds was investigated. The drug release rate increased with the increase of chitosan content because the addition of chitosan enhanced the hydrophilicity of the PLGA/chitosan composite scaffold. Moreover, for the aligned PLGA/chitosan nanofibrous scaffold the release rate was lower than that of randomly oriented PLGA/chitosan nanofibrous scaffold, which indicated that the nanofiber arrangement would influence the release behavior. In addition, crosslinking in glutaraldehyde vapor would decrease the burst release of FBF from FBF-loaded PLGA/chitosan nanofibrous scaffold with a PLGA/chitosan ratio less than 9/1, which would be beneficial for drug release.     

Effect of chain conformation on micro-mechanical behaviour of MEH–PPV thin film

The morphology, photoluminescent properties and micro-mechanical character of poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH–PPV) thin films prepared from toluene (T film) and chloroform (C film) were studied by transmission electron microscopy (TEM), absorption, photoluminescence spectrophotometry and nanoindentation test. The morphological feature of worm-like entities which appeared in T film was ~10–20 nm in length and 3–5 nm in width. The C film displayed the continuous cotton fibre-shaped morphology. In contrast with C film, the band-edge absorption and maximum emission for T film shifted to the longer wavelength. An analysis from TEM photograph, absorption and photoluminescence spectra indicated that different chain conformation presented in these two kinds of films. The nanoindentation test showed that the elastic modulus and indentation hardness of T film under the same experimental parameter (load: 50–200 μN, loading rate: 20 μN/s and holding time: 20 s) decreased by 33·3 ± 0·3 and 8·9 ± 0·5%, respectively comparing with C film. In addition, critical bending radius of these two films based on the flexible base was also evaluated from the obtained experimental results.     

Dependence of thermal conductivity in micro to nano silica

This work presents the measurement of thermal conductivity of nano-silica particles using needle probe method. The validation test of thermal probe was conducted on ice and THF hydrates using our experimental set up and the results are satisfactory when compared with the literature data. The nano silica used in this study is with particle sizes in the range 50–1000 nm. The sand powders sieved in different sizes ?<75 and 75  μ m ?>? d ?>? 250  μ m were also studied to probe the particle size dependence on thermal conductivity. Thermal conductivity decreased by about 70% in silica nano powders.