Novel bone scaffolds of electrospun polycaprolactone fibers filled with nanoparticles

Novel bone scaffolding materials were successfully fabricated by electrospinning from polycaprolactone (PCL) solutions containing nanoparticles of calcium carbonate (CaCO3) or hydroxyapatite (HA). The potential use of the electrospun fibrous scaffolds for bone regeneration was evaluated in vitro with human osteoblasts (SaOS2) in terms of attachment, proliferation, and alkaline phosphatase (ALP) activity of the cells that were cultured directly on the scaffolds. The results were compared with those on corresponding solution-cast film scaffolds and tissue-culture polystyrene plate (TCPS). It was found that all of the fibrous scaffolds promoted much better adhesion and proliferation of cells than the corresponding film scaffolds and TCPS. Interestingly, the cells that were seeded on all of the fibrous scaffolds appeared to be well-expanded and attach on the fiber surface very well even only about 1 hr in culture, while those seeded on all of the film scaffolds and the glass substrate were still in round shape. Among the various fibrous scaffolds investigated, the one that was filled with 1.0% HA showed the highest ALP activity. Finally, all of the fibrous scaffolds exhibited much greater tensile strength at yield than all of the corresponding film scaffolds.     

同轴静电纺再生丝素/丝胶蛋白纤维的制备及其形态结构表征

模仿蚕丝的组成和结构,利用同轴静电纺丝法制备了以再生丝素蛋白（RSF）为＂芯＂、丝胶蛋白（SS）为＂皮＂的双组分静电纺纤维。通过扫描电镜和透射电镜研究了内层纺丝液流速（Qc）、电压（U）、接收距离（D）以及场强（E）等参数对同轴静电纺RSF/SS纤维形态结构的影响。研究结果表明纤维的平均直径在1400～2100nm左右,皮-芯层结构清晰;Qc对纤维皮-芯层结构的影响较大,过大的内层纺丝液流速会因外层丝胶对内层丝素的包裹不均匀而导致偏芯现象;随E的增加（U增加或D减小）,纤维的直径及其分布显著减小,皮-芯层结构清晰;相同E下,高电压、长距离利于纤维的细化,使直径变细且分布均匀,皮-芯层结构明显。     

Fabrication of fluorescence tunable electrospun conjugated polycarbazole fibers containing gold nanoparticles

In this report, we demonstrate a novel way to tune the fluorescence property of electrospun conjugated polymer fibers. The basic strategy is to use a soluble precursor polymer with gold nanoparticles for electrospinning, which is then cross-linked by applying potential cycles in an electrochemical cell. Electroactive carbazole units in electrospun precursor polymer fibers were converted to conjugated polymer fibers. Since the conjugated polymer fibers can be formed, the fluorescence from the conjugated polymer fibers can be tuned by the rate of the conversion and doping of the fibers. Furthermore, the quenching of the fluorescence, which overlaps with the plasmon band of the gold nanoparticles, was observed. The quenching of the fluorescence properties of the fibers was dependent on the amount of gold nanoparticles inside the fibers.     

Oxygen detection using UV-activated electrospun poly(ethylene oxide) fibers encapsulated with TiO2 nanoparticles

A UV-activated oxygen indicator was developed in this study. The indicator was prepared by dispersing TiO₂ nanoparticles, glycerol, and methylene blue in poly(ethylene oxide) solution using aqueous ethanol as a solvent. The solution was electrospun or solvent cast to produce oxygen-sensitive fibrous membrane and continuous cast film, respectively. Sensitivity characteristics of the resulting indicators to UV irradiation and oxygen detection, at different component ratios, were evaluated. Scanning electron microscopy results show that the diameter of the electrospun fibers varied from about 350 to 1000 nm. The electrospun indicators were 4–5 times more sensitive to UV irradiation as compared to continuous film indicators prepared by casting, mainly due to morphological differences between the two poly(ethylene oxide) carriers. Increasing ethanol concentration of the electrospinning solvent enhanced the sensitivity of the indicator to UV irradiation. Moreover, the photo-bleaching step of the indicator was highly dependent on the active component ratios in the formulation. FTIR spectroscopy was employed to study the interactions between the active compounds in the indicator. This study demonstrated that electrospun TiO₂-based indicator could be promising for oxygen detection in modified atmosphere packaging applications.     

A novel electrospun silk fibroin/hydroxyapatite hybrid nanofibers

A novel electrospinning of silk fibroin/hydroxyapatite hybrid nanofibers with different composition ratios was performed with methanoic acid as a spinning solvent. The silk fibroin/hydroxyapatite hybrids containing up to 30% hydroxyapatite nanoparticles could be electrospun into the continuous fibrous structure. The electrospun silk fibroin/hydroxyapatite hybrid nanofibers showed bigger diameter and wider diameter distribution than pure silk fibroin nanofibers, and the average diameter gradually increased from 95 to 582 nm. At the same time, the secondary structure of silk fibroin/hydroxyapatite nanofibers was characterized by X-ray diffraction, Fourier transform infrared analysis, and DSC measurement. Comparing with the pure silk fibroin nanofibers, the crystal structure of silk fibroin was mainly amorphous structure in the hybrid nanofibers. X-ray diffraction results demonstrated the hydroxyapatite crystalline nature remained as evidenced from the diffraction planes (002), (211), (300), and (202) of the hydroxyapatite crystallites, which was also confirmed by Fourier transform infrared analysis. The thermal behavior of hybrid nanofibers exhibited the endothermic peak of moisture evaporation ranging from 86 to 113 °C, and the degradation peak at 286 °C appeared. The SF/HAp nanofibers mats containing 30% HAp nanoparticles showed higher breaking tenacity and extension at break for 1.1688 ± 0.0398 MPa and 6.55 ± 1.95%, respectively. Therefore, the electrospun silk fibroin/hydroxyapatite hybrid nanofibers should be provided potentially useful options for the fabrication of biomaterial scaffolds for bone tissue engineering.     

Ultrafine porous fibers electrospun from cellulose triacetate

Ultrafine porous cellulose triacetate (CTA) fibers were prepared by electrospinning with methylene chloride (MC) and a mixed solvent of MC/ethanol (EtOH) and their intra- and inter-fiber pore structures was investigated. Ultrafine porous CTA fibers electrospun with MC had isolated circular shape pores with a narrow size distribution in the range of 50–100 nm. In the case of ultrafine CTA fibers electrospun with MC/EtOH (90 / 10 v/v), they had interconnected larger pores in the range of 200–500 nm. These porous structures were induced by phase separation resulting from the rapid evaporation of solvent during the electrospinning process. However, non-porous corrugated fibers were obtained from MC/EtOH (85 / 15 v/v) and MC/EtOH (80 / 20 v/v) due to their lower vapor pressure. The pore sizes in ultrafine CTA fibers electrospun with MC showed a bimodal distribution centered at ∼17 and ∼64 nm. CTA fibers electrospun with MC/EtOH (90 / 10 v/v) showed the greatest porosity due to their larger intra-fiber pores and fiber diameter.     

壳-芯电纺超细纤维作为药物释放载体的研究

应用同轴共纺技术制备了以L-型聚乳酸为壳层材料,盐酸四环素为主要芯质材料的壳-芯超细纤维膜,研究了这种超细纤维膜的微观结构、力学性能与药物释放特性.结果表明,药物能够包覆在一层很薄的可降解聚合物壳层中,形成一种储库型药物释放系统.纤维的直径大小对纤维膜的各项理化性能有较大影响.随壳层聚合物浓度升高,纤维的平均直径增大,力学强度降低.药物能够从纤维膜中持续释放出来.这种壳-芯超细纤维有望用于药物释放、载药缝合线和医用敷料等生物医学领域.     

Preparation and characterization of electrospun nanofibers based on silk sericin powders

The present contribution reports the fabrication and characterization of silk sericin (SS) nanofibers via electrospinning. The function of solution concentration on morphological appearance and average diameter of the electrospun SS membranes was investigated by scanning electron microscopy. The structure and physical properties were observed by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). All beads were acquired in lower concentration of SS solution, 1.3–8.5 wt% of SS solutions, and beaded fibers were produced from 9.6, 11.7, 14.2, and 16.5 wt% of SS solution. The perfect nanofibers acquiring average diameters of 145 and 184 nm were fabricated from 20.9 to 22.9 wt% of SS solution, respectively. Results from FT-IR showed that in the as-spun fibers, SS was present in a random coil conformation, while after heat treatment, the molecular structure of SS was transformed into a β-sheet containing structure. DSC and TG analysis illustrated that trifluoroacetic acid can be eliminated by heating. The availability of SS nanofibers introduces a new set of possible uses of these amazing fibers at a scale not explored before. New uses include small diameter fibers for cell proliferation purposes, nanocomposite reinforcing fibers for nanotechnology, wound dressing, scaffolds for tissue engineering, and other biomedical applications.     

静电纺丝素蛋白纤维毡在乙醇水溶液中的拉伸后处理

利用静电纺丝技术制备了再生丝素蛋白纤维毡,并采用乙醇水溶液对其进行拉伸后处理以提高其力学性能。研究了乙醇的体积分数对纤维毡形貌、结构和性能的影响。结果表明,随乙醇体积分数的增加,纤维毡中β-折叠结构的含量增加。纤维毡在体积分数为90%的乙醇溶液中,先拉伸1.11倍,然后浸泡120min后,其断裂强度及断裂伸长率分别达2.64MPa和12.1%。     

Electrospun ultra-fine silk fibroin fibers from aqueous solutions

By using electrospinning technique, beaded, cylinder shaped and ribbon like ultra-fine silk fibroin (SF) fibers were obtained from its concentrated aqueous solution under different processing conditions. These fibers had an average diameter of 700 nm and were characterized by scanning electron microscopy (SEM), Wide-angle X-ray diffraction (WAXD) and Raman spectroscopy. It was found that the morphology and the secondary structure of the as-spun SF fibers were strongly influenced by the solution concentration, as well as the processing voltage. By adjusting these technological parameters, β-sheet conformation and silk II crystal structure of the SF fibers can be formed without any post-treatment.     

Fabrication and electromechanical characterization of near-field electrospun composite fibers

We report the use of near-field electrospinning (NFES) as a route to fabricate composite electrodes. Electrodes made of composite fibers of multi-walled carbon nanotubes in polyethylene oxide (PEO) are formed via liquid deposition, with precise control over their configuration. The electromechanical properties of free-standing fibers and fibers deposited on elastic substrates are studied in detail. In particular, we examine the elastic deformation limit of the resulting free-standing fibers and find, similarly to bulk PEO composites, that the plastic deformation onset is below 2% of tensile strain. In comparison, the apparent deformation limit is much improved when the fibers are integrated onto a stretchable, elastic substrate. It is hoped that the NFES fabrication protocol presented here can provide a platform to direct-write polymeric electrodes, and to integrate both stiff and soft electrodes onto a variety of polymeric substrates.     

Synthesis of silver chloride nanocrystal on silk fibers

The synthesis of silver chloride nanocrystals on silk fiber is reported. The growth of the nanocrystal was achieved by sequential dipping of the silk fibers in alternating solution of either silver nitrate or sodium chloride followed by a rinse step. The negative charge present at the surface of the fibers can immobilize silver ions which react in the next sodium chloride bath to form an initiator seed of silver chloride. The repeated alternating dipping of the fiber in the different solutions leads to the growth of AgCl nanocrystals. After 20 alternating dipping steps, the formation of cubic AgCl nanocrystal was observed by SEM, which revealed the presence of 100 nm cubes on the silk fiber. The crystallographic nature of the AgCl crystals was confirmed by X-ray diffraction which confirmed the presence of characteristics diffraction peak of AgCl and a cell size of 5.549 Å. The resulting fiber coated with nano-AgCl crystals could be used as a photocatalyst in water splitting applications or as an antibacterial agent.     

Antibacterial activity of electrospun polymer mats with incorporated narrow diameter single-walled carbon nanotubes

Polymer coatings featuring nonleaching antibacterial agents are needed to significantly reduce bacterial colonization and subsequent biofilm formation. Previously, single-walled carbon nanotubes (SWNTs) have been reported to be strong antimicrobial agents that kill microbes on contact. However, the antibacterial activity of freestanding polymer mats with a low weight percent of incorporated SWNTs has not been demonstrated. In this study, four different weight percents of well characterized, small diameter (0.8 nm) SWNTs were incorporated into electrospun polysulfone (PSf) mats. Electrospun PSf-SWNT mats were observed to be flexible and composed of continuous, cylindrical, and randomly oriented fibers. SEM micrographs revealed that SWNT ends were distributed along the longitudinal fiber axis. Loss of bacteria (Escherichia coli) viability was observed to directly correlate to increased SWNT incorporation within the mat, ranging from 18% for 0.1 wt % SWNTs to 76% for 1.0 wt % SWNTs. Time-dependent bacterial cytotoxicity studies indicated that the antimicrobial action of the PSf-SWNT mats occurs after a short contact time of 15 min or less. This study demonstrates the potential applicability of electrospun PSf-SWNT mats as antibacterial coatings.     

电纺碳基纤维材料电催化水分解制氢

电解水制氢是由阴极析氢反应(HER)和阳极析氧反应(OER)组成。由于HER和OER所需的过电位高,反应动力学迟缓,导致电解水槽电压远高于理论平衡电压,电能消耗严重。因此,探索高效、稳定的非贵金属基电催化剂具有重要的研究意义。利用静电纺丝技术构筑的纤维材料因其较大的比表面积、独特的化学结构、易于调节的组分以及快速的电子和物质传输性能而被广泛应用在能源转化与存储领域。基于此,综述了近几年电纺碳基纤维材料在电催化水分解制氢中的研究进展,重点关注了静电纺丝技术制备的纳米纤维电催化剂用于HER、OER以及作为双功能催化剂在全水分解中产生高催化性能的优势,并对电纺材料在电催化水分解中的应用特点及其未来可能面临的挑战和发展趋势进行了展望。     

Down conversion photoluminescence on PVP/Ag-nanoparticles electrospun composite fibers

The influence of Ag nanoparticles (Ag NPs) on the luminescence of electrospun nonwoven mats made of polyvinylpyrrolidone (PVP) has been studied in this work. The PVP fibers incorporating 2.1–4.3 nm size Ag NPs show a significant photoluminescence (PL) band between 580 and 640 nm under 325 nm laser excitation. The down conversion luminescence emission is present even after several hours of laser excitation, which denotes the durability and stability of fibers to consecutive excitations. As so these one-dimensional photonic fibers made using cheap methods is of great importance for organic optoelectronic applications, fluorescent clothing or counterfeiting labels.     

Catalytic activity of gold nanoparticles incorporated into modified zeolites

Gold catalysts modified by Fe and Ni and supported on different zeolite matrixes have been studied by TEM, TPR, and catalytic testing. The presence of a metal oxide additive allows stabilizing small gold particles, particularly in the case of Fe. The shape of light-off curves shows two temperature regions of the catalyst activity, a low-temperature range below 250 degrees C and a high-temperature range above 300 degrees C. This situation is explained considering the existence of at least two types of catalytically active sites of gold assigned to gold clusters and gold nanoparticles, respectively, while the ionic state of gold (Au3+) remains inactive. It is shown that interaction of gold with Fe promoter leads to activation of catalysts at low temperature due to a change of electronic state and redox properties of gold. NiO additive cause a similar, but less pronounced effect.     

Novel alginate based nanocomposite hydrogels with incorporated silver nanoparticles

Alginate colloid solution containing electrochemically synthesized silver nanoparticles (AgNPs) was investigated regarding the nanoparticle stabilization and possibilities for production of alginate based nanocomposite hydrogels in different forms. AgNPs were shown to continue to grow in alginate solutions for additional 3 days after the synthesis by aggregative mechanism and Ostwald ripening. Thereafter, the colloid solution remains stable for 30 days and could be used alone or in mixtures with aqueous solutions of poly(vinyl alcohol) (PVA) and poly(N-vinyl-2-pyrrolidone) (PVP) while preserving AgNPs as verified by UV–Vis spectroscopy studies. We have optimized techniques for production of Ag/alginate microbeads and Ag/alginate/PVA beads, which were shown to efficiently release AgNPs decreasing the Escherichia coli concentration in suspensions for 99.9% over 24 h. Furthermore, Ag/hydrogel discs based on alginate, PVA and PVP were produced by freezing-thawing technique allowing adjustments of hydrogel composition and mechanical properties as demonstrated in compression studies performed in a biomimetic bioreactor.