Hybrid composite of Nafion with surface-modified electrospun polybenzoxazine (PBz) fibers via ozonation as fillers for proton conducting membranes of fuel cells

Nafion was investigated for its compatibility in the preparation of hybrid composites with electrospun Polybenzoxazine (PBz) surface-modified fibers by evaluating the effects on the surface and structure of the composite. A PBz fiber mat was first crosslinked by thermal treatment after electrospinning to enhance the mechanical integrity of the fibers prior to modification. Further surface modification via free radical ozonation was carried out by potentiating oxygen-based functional groups of hydroxyl radicals (–OH) onto fibers'' exposed surfaces. The sequential modifications by crosslinking and ozone treatment were evaluated by analyzing surface properties using XPS, ATR-FTIR and water contact angle which determined the enhanced properties of the fibers that were beneficial to the target functionality. Electron spectroscopy confirmed that fibers'' surfaces were changed with the new surface chemistry without altering the chemical structure of PBz. The presence of higher oxygen-based functional groups on fibers'' surfaces based on the resulting atomic compositions was correlated with the change in surface wettability by becoming hydrophilic with contact angle ranging from 21.27° to 59.83° compared to hydrophobic pristine PBz fibers. This is due to electrophilic aromatic substitution with hydroxyl groups present on the surfaces of the fibers endowed by ozonation. The resulting surface-modified fiber mat was used for the preparation of composites by varying two process parameters, the amount of Nafion dispersion and its homogenization and curing time, which was evaluated for compatibility and interaction as fillers to form hybrid composites. The analyses of SEM images revealed the effects of shorter homogenization and curing time on composites with rougher and wrinkled surfaces shown on the final hybrid composite''s structure while decreasing the amount of Nafion at the same homogenization time but longer curing time showed its influence on improvement of compatibility and surface morphology.

Nafion compatibility in the preparation of hybrid composites with electrospun Polybenzoxazine (PBz) surface-modified fibers via ozonation by evaluating the effects on the surface and structure of the composite.     

静电纺壳聚糖/胶原蛋白复合纳米纤维的细胞相容性

目的:静电纺是一种使带电荷的聚合物溶液或熔体在静电场中射流来制备聚合物纳米级纤维的加工方法,采用此种技术制备壳聚糖/胶原蛋白复合纳米纤维,并观察其细胞相容性.方法:实验于2006-11/2007-10在东华大学化学化工与生物工程学院生物材料与组织工程实验室完成.①支架材料制备:以六氟异丙醇/三氟乙酸为溶剂体系,采用静电纺制备复合纳米纤维,其中壳聚糖/胶原蛋白的质量比分别为100:0,80:20,50:50,20:80与0:100.②细胞相容性观察:体外接种猪髋动脉内皮细胞,苏木精-伊红染色法观察细胞形态,MTT法检测细胞黏附和增殖情况.结果:猪髋动脉内皮细胞在壳聚糖/胶原蛋白复合纤维表面贴附牢固,外形饱满,多呈长梭形,具有良好的生长形态;MTT法结果显示纳米纤维能够有效地促进内皮细胞在材料表面的黏附和增殖,质量比为20:80材料组细胞黏附、增殖能力最强,其次为50:50组.结论: 静电纺壳聚糖/胶原蛋白复合纳米纤维具有良好的细胞相容性,可望成为一种新型的组织工程支架材料.     

Thermal conductivity of polyurethane sheets containing beryllium oxide nanofibers

Polyvinyl alcohol/beryllium sulfate/polyethyleneimine (PVA/BeSO₄/PEI) precursor nanofibers (NFs) was first fabricated to obtain PVA/BeSO₄/PEI electrospun NFs by electrospinning technology, finally manufactured beryllium oxide (BeO) NFs followed by various heat treatment methods. The minimum calcination temperature for pure BeO NFs was 1000 °C, and the minimum specific surface area (5.1 m² g⁻¹) and pore volumes (0.0128 cm³ g⁻¹) were at 1300 °C. 46.18% Be and 53.82% O was measured in BeO NFs by X-ray photoelectron spectroscopy. BeO NFs were then impregnated with polyurethane (PU) aqueous solution to make PU/BeO NFs heat-dissipating sheet. This heat-dissipating sheet showed superior thermal conductivity (14.4 W m⁻¹ K⁻¹) at 41.4 vol% BeO NFs content. The electrical insulating properties of the heat-dissipating sheet were likewise excellent (1.6 × 10¹² Ω □⁻¹). In this study, the author attempted to create a thermally conductive but electrically insulating PU/BeO NFs heat-dissipating sheet that could effectively eliminate generated heat from electric equipment.

The BeO NFs’ elongated shape, which provides excellent heat pathways for the BeO NFs in the resin.     

两种聚（左旋乳酸-己内酯）静电纺纳米纤维膜的性能比较

背景:聚左旋乳酸和聚己内酯各自都有其优点与缺点,而共聚或共混后性能可以得到有效的改善,但因为两者添加比例的不同会对性能有一定的影响,在不吲的纺丝溶液浓度下纺出的纤维性能亦会有所差异.目的:通过对两种原料聚(左旋乳酸-己内酯)(75/25;50/50)在不同纺丝液浓度下制得的纳米纤维膜各种性能的比较,选出最佳的原料和相应的纺丝液浓度.设计、时间及地点:对比观察实验,于2007-09/2008-11在东华大学生物材料与组织工程实验室完成.材料:将聚聚(左旋乳酸-己内酯)材料在乳酸/己内酯为75/25和50/50两种比例下,在质量分数为4%,6%,8%和10%纺丝液浓度下通过静电纺丝制备纳米纤维膜.方法:扫描电镜样品经表面喷金后在10 kV加速电压下观察纤维膜的彤貌.在万能材料测试机测试其断裂强度和断裂伸长率.采用MTT法测试猪髋动脉内皮细胞在纳米纤维膜上的黏附与增殖情况.主要观察指标:静电纺纳米纤维膜的纤维形态、力学性能及生物相容性.结果:通过扫描电镜观察发现由质量分数为6%聚(左旋乳酸-己内酯)(50/50)制备的纤维膜具有更好的纤维形态,且直径分布均匀;拉伸力学测试显示由聚(左旋乳酸-己内酯)(50/50)制备的纤维膜比聚(左旋乳酸-己内酯)(75/25)具有更高的断裂伸长率,但断裂应力较低;细胞生物相容性实验表明猪髋动脉内皮细胞在质鼍分数为6%和8%聚(左旋乳酸-己内酯)(50/50)的纳米纤维膜上更能有效的黏附与增殖.结论:纺丝液质量分数为6%的聚(左旋乳酸-己内酯)(50/50)制得的纳米纤维膜各项性能较优.     

Anti microbial corrosion properties of electrospun cellulose acetate nanofibers containing biogenic silver nanoparticles for copper coatings

Nanofibers with inorganic nanoparticles are novel hybrid nanocomposites that have great potential in various areas. In the present study, cellulose acetate nanofibers (CA-Nf) loaded with biogenic silver nanoparticles were prepared and characterized. In situ synthesis of silver nanoparticles was accomplished using a bacteria free solution as a reducing agent. Nanofibers incorporated with silver nanoparticles were fabricated using the electrospinning technique. Upright microscopy and SEM micrographs depicted that the CA-Nf coatings consist of dense and compact entangled nanofibers that completely cover the copper surface. Corrosion measurements were performed by potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) techniques on the bare copper and CA-Nf and CA-Nf_5% AgNp coated copper surfaces in artificial seawater (ASW) and Escherichia coli ATCC 13883 inoculated solutions. Weight loss and electrochemical corrosion test results revealed that the CA-Nf-coated copper had greater corrosion resistance than bare copper. The additional electrospun CA-Nf_5% AgNp coating also had greater antibacterial behavior toward model biofilm bacterium Pseudomonas aeruginosa than uncoated copper specimens. Therefore, this nanofiber with AgNps was demonstrated as an efficient anticorrosive material in both corrosive and biocorrosive marine solutions.

Nanofibers with inorganic nanoparticles are novel hybrid nanocomposites that have great potential in various areas.     

Nanocomposite membranes of polybenzimidazole and amine-functionalized carbon nanofibers for high temperature proton exchange membrane fuel cells

Carbon nanofibers functionalized with aminobenzoyl groups (CNF–aminobenzoyl) were prepared via direct Friedel–Crafts acylation in polyphosphoric acid. The functionalization of CNFs was characterized using XPS, FTIR, TGA, and Raman analyses. Hexafluoroisopropylidene-containing polybenzimidazole (6FPBI) composite membranes containing pristine CNFs or CNF–aminobenzoyl were prepared using solvent-assisted dispersion and solvent-casting methods. In this work, the influence of the incorporation of functionalized CNFs on several physicochemical properties of the 6FPBI nanocomposite membranes, including their thermal stability, mechanical strength, and acid doping level, was studied. The results showed that CNF–aminobenzoyl provided better mechanical reinforcement for the nanocomposite membrane, compared to pristine CNF. The SEM observation confirmed the good compatibility between the CNF–aminobenzoyl fillers and the 6FPBI matrix. For the 0.3 wt% CNF–aminobenzoyl/6FPBI composite membrane, the tensile stress was increased by 12% to be 78.9 MPa (as compared to the 6FPBI membrane), the acid doping level was improved to 12.0, and the proton conductivity at 160 °C was measured above 0.2 S cm⁻¹. Furthermore, the fuel cell performance of the membrane electrolyte assembly (MEA) for each nanocomposite membrane was evaluated. The maximum power density at 160 °C was found up to 461 mW cm⁻² for the MEA based on the 0.3 wt% CNF–aminobenzoyl/6FPBI composite membrane.

Carbon nanofibers functionalized with aminobenzoyl groups (CNF–aminobenzoyl) were prepared via direct Friedel–Crafts acylation in polyphosphoric acid.     

Preparation and electrochemical studies of electrospun phosphorus doped porous carbon nanofibers

An ultra-facile fabrication process for the preparation of phosphorus doped porous carbon nanofibers (P-PCNFs) through the electrospinning and heat treatment method has been studied. The materials were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Studies showed that fabricated P-PCNFs have unique porous fibers structures, large specific surface area (462.83 cm² g⁻¹), and abundant microporous and mesoporous structures. X-ray photoelectron spectroscopy analyses revealed that the contents of phosphorus and electrochemical properties in a series of P-PCNF samples can be tuned by controlling the polyphosphoric acid concentration. The electrochemical properties of the materials were evaluated using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. Studies showed that the specific capacitance of the fabricated P-PCNFs using the ultra-facile process reached up to 228.7 F g⁻¹ at 0.5 A g⁻¹ in 1 M H₂SO₄. Over 84.37% of the initial capacitance remains as the current density increases from 0.5 to 10 A g⁻¹. Meanwhile, at a current density of 2 A g⁻¹, no capacitance loss was observed in 5000 charge/discharge cycles. The highest voltage windows of sample P-PCNFs-1.0 in 1 M H₂SO₄ aqueous electrolyte can reach 1.4 V. These properties suggest that the fabricated P-PCNFs exhibit excellent electrochemical properties. Conclusively, the surface of carbon nanofibers can be modified by heteroatom doping or surface activation which can improve the electrochemical performance of the materials.

Preparation of phosphorus-doped porous carbon nanofibers, with excellent capacitance properties, by electrospinning, using polyethylene glycol as a pore-making agent and polyphosphoric acid as a phosphorus source.     

Acidity effects of medium fluids on anhydrous proton conductivity of acid-swollen block polymer electrolyte membranes

Proton-conductive polymer electrolyte membranes (PEMs) were prepared by infiltrating sulfuric acid (Sa) or phosphoric acid (Pa) into a polystyrene-b-poly(4-vinylpyridine)-b-polystyrene (S–P–S) triblock copolymer. When the molar ratio of acid to pyridyl groups in S–P–S, i.e., the acid doping level (ADL), is below unity, the P-block/acid phase in the PEMs exhibited a moderately high glass transition temperature (T_g) of ∼140 °C because of consumption of acids for forming the acid–base complexes between the pyridyl groups and the acids, also resulting in almost no free protons in the PEMs; therefore, the PEMs were totally glassy and exhibited almost no anhydrous conductivity. In contrast, when ADL is larger than unity, the T_gs of the phase composed of acid and P blocks were lower than room temperature, due to the excessive molar amount of acid serving as a plasticizer. Such swollen PEMs with excessive amounts of acid releasing free protons were soft and exhibited high conductivities even without humidification. In particular, an S–P–S/Sa membrane with ADL of 4.6 exhibited a very high anhydrous conductivity of 1.4 × 10⁻¹ S cm⁻¹ at 95 °C, which is comparable to that of humidified Nafion membranes. Furthermore, S–P–S/Sa membranes with lower T_gs exhibited higher conductivities than S–P–S/Pa membranes, whereas the temperature dependence of the conductivities for S–P–S/Pa is stronger than that for S–P–S/Sa, suggesting Pa with a lower acidity would not be effectively dissociated into a dihydrogen phosphate anion and a free proton in the PEMs at lower temperatures.

Sulfuric acid-swollen block polymer membranes exhibit anhydrous conductivities of ∼0.1 S cm⁻¹ that is higher than those of phosphoric acid-swollen membranes, whereas temperature dependence of conductivities of the latter is stronger than the former.     

利用Collagen/PLCL复合纳米纤维电纺膜构建组织工程化气管补片的初步研究

目的初步探讨以胶原/聚左旋乳酸-己内酯共聚物(Collagen/PLCL)复合纳米纤维电纺膜作为支架材料复合肋软骨细胞构建组织工程化气管补片的可行性。方法分离及培养2月龄新西兰兔肋软骨细胞,取第二代肋软骨细胞种植于Collagen/PLCL复合纳米纤维电纺膜,并进行扫描电镜观察,然后利用"三明治"法构建成细胞材料复合物,体外培养4周再植入裸鼠背部皮下,4周后取出进行大体观察、组织学染色以及Ⅱ型胶原免疫组织化学检测以评价组织成软骨效果。结果扫描电镜显示肋软骨细胞在该材料上黏附生长良好,细胞材料复合物在体内培养4周后已形成类软骨样组织,组织学检查HE染色可见有大量软骨陷窝形成,甲苯胺蓝、番红O染色可见有大量软骨基质分泌,Ⅱ型胶原免疫组织化学染色呈阳性表达提示该组织含有软骨组织特有的Ⅱ型胶原。结论 Collagen/PLCL复合纳米纤维电纺膜对于兔肋软骨细胞具有良好的生物相容性,复合肋软骨细胞形成的组织工程化软骨类似于正常透明软骨组织,适合于构建组织工程化气管补片。     

电纺胶原和蛛丝纳米纤维膜的制备、表征及生物安全性比较

目的:制备胶原和蜘蛛丝两种纳米纤维膜,进行理化性能表征和生物相容性比较,以期将蜘蛛丝纳米纤维用于组织工程支架材料.方法:实验于2006-07/2007-08在上海市东华大学生物科学与技术研究所完成.将胶原和蜘蛛丝分别以80 g/L溶于六氟异丙醇,采用高15 kV压静电纺制成纳米纤维膜,真空干燥后对其理化性能进行表征.扫描电镜观察超微结构,并进行水接触角测量和水解稳定性测量;并采用MTT实验比较猪大动脉内皮细胞在两种纤维膜表面的黏附、生长和增殖等情况.结果:①静电纺胶原和蛛丝纳米纤维膜均具有良好三维多孔结构,但蛛丝纤维直径更均匀.蛛丝膜具有较大的水接触角,在水解稳定性测试中质量损失较少.②MTT实验表明,种植6 h后血管内皮细胞在胶原和蛛丝膜上都能黏附,但蛛丝膜上细胞增殖速度较快,2 d后超过胶原膜,7 d后蛛丝膜上细胞多于胶原膜表面40%以上.结论:胶原和蛛丝都能促进血管内皮细胞黏附、生长.蛛丝膜具有较强的疏水性和水解稳定性,在体外培养过程中蛛丝更有利于细胞增殖,有望作为血管组织工程支架材料.     

Synthesis of self-assembled nucleobases and their anhydrous proton conductivity

We synthesized self-assembled nucleobases (SANs), such as 1-dodecylthymine (DOT) or 9-dodecyladenine (DOA), in which the nucleobase is immobilized on a long alkyl chain. The thermal stability of the SAN was increased by mixing with the acidic surfactant mono-dodecyl phosphate (MDP). Additionally, the SAN–MDP composite material showed proton conductivity of 4.62 × 10⁻⁴ S cm⁻¹ at 160 °C under anhydrous conditions. Additionally, the activation energy of the proton conduction was approximately 0.2 eV and this value was one order of magnitude higher than that of a typical humidified perfluorinated membrane, in which the proton can be moved by vehicle molecules, such as water molecules. In contrast, when the nucleobase without the immobilization of a long alkyl chain was mixed with MDP, the proton conductivity of these composite materials was two orders of magnitude less than that of the SAN–MDP composite. Therefore, we measured the XRD spectra of the SAN–MDP composite material. As a result, the SAN–MDP composite material showed a self-assembled structure with a two-dimensional proton conducting pathway, such as a lamellar structure, and that the anhydrous proton conduction was related to the interaction between the nucleobase of the SAN and the phosphate group of MDP. Consequently, the self-assembled nucleobase derivatives have the potential for use as novel anhydrous proton conductors with a two-dimensional proton conducting pathway.

We synthesized the proton conductive self-assembled nucleobase, such as 1-dodecylthymine and 9-dodecyladenine, in which the nucleobase is immobilized on a long alkyl chain.     

Sulfonated graphene oxide/Nafion composite membranes for high temperature and low humidity proton exchange membrane fuel cells

Iron oxide (Fe₃O₄) nanoparticles anchored over sulfonated graphene oxide (SGO) and Nafion/Fe₃O₄–SGO composites were fabricated and applied as potential proton exchange membranes in proton exchange membrane fuel cells (PEMFCs) operated at high temperature and low humidity. Fe₃O₄ nanoparticles bridge SGO and Nafion through electrostatic interaction/hydrogen bonding and increased the intrinsic thermal and mechanical stabilities of Nafion/Fe₃O₄–SGO composite membranes. Nafion/Fe₃O₄–SGO composite membranes increased the compactness of ionic domains and enhanced the water absorption and proton conductivity while restricting hydrogen permeability across the membranes. The proton conductivity of Nafion/Fe₃O₄–SGO (3 wt%) composite membrane at 120 °C under 20% relative humidity (RH) was 11.62 mS cm⁻¹, which is 4.74 fold higher than that of a pristine recast Nafion membrane. PEMFC containing the Nafion/Fe₃O₄–SGO composite membrane delivered a peak power density of 258.82 mW cm⁻² at a load current density of 640.73 mA cm⁻² while operating at 120 °C under 25% RH and ambient pressure. In contrast, under identical operating conditions, a peak power density of only 144.89 mW cm⁻² was achieved with the pristine recast Nafion membrane at a load current density of 431.36 mA cm⁻². Thus, Nafion/Fe₃O₄–SGO composite membranes can be used to address various critical problems associated with commercial Nafion membranes in PEMFC applications.

Preparation process of Nafion/Fe₃O₄–SGO composite membranes.     

Preparation and characterization of antibacterial dopamine-functionalized reduced graphene oxide/PLLA composite nanofibers

Electrospun poly(l)-lactide (PLLA) ultrafine fibers are a biodegradable and biocompatible scaffold, widely used in tissue engineering applications. Unfortunately, these scaffolds have some limitations related to the absence of bioactivity and antibacterial capacity. In this study, dopamine-functionalized reduced graphene oxide (rGO)/PLLA composite nanofibers were fabricated via electrospinning. The morphology and the physicochemical and biological properties of the composite nanofibers were investigated. The results indicate that incorporating rGO improves the hydrophilic, mechanical, and biocompatibility properties of PLLA nanofibers. Tetracycline hydrochloride (TC)-loaded rGO/PLLA composite nanofibers showed better controlled drug release profiles compared to GO/PLLA and PLLA nanofibrous scaffolds. Drug-loaded nanofibrous scaffolds showed significantly improved antibacterial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Additionally, rGO/PLLA composite nanofibers exhibited enhanced cytocompatibility. Thus, it can be concluded that rGO/PLLA composite nanofibers allow the development of multifunctional scaffolds for use in biomedical applications.

Antibacterial dopamine-functionalized reduced graphene oxide (rGO)/PLLA composite nanofibers for biomedical applications.     

新型多孔偏磷酸钙复合膜的制备及细胞相容性*

背景：前期研究制备的多孔聚3-羟基丁酸-4-羟基丁酸/偏磷酸钙复合膜厚度较厚,且孔洞不均匀。
　　目的：制备厚度薄且分布均匀的多孔聚3-羟基丁酸-4-羟基丁酸/偏磷酸钙复合膜,检测其细胞相容性及对细胞分化的作用。
　　方法：通过相分离法制备厚度薄且分布均匀的无孔及多孔聚3-羟基丁酸-4-羟基丁酸/偏磷酸钙复合膜,检测其厚度及失重率。将人骨髓间充质干细胞分别与无孔及多孔聚3-羟基丁酸-4-羟基丁酸/偏磷酸钙复合膜共培养7 d,扫描电镜观察复合膜的超微结构,流式细胞术分析复合膜上骨髓间充质干细胞的表面标记物。
　　结果与结论：多孔和无孔复合膜的厚度分别为(0.041±0.005) mm和(0.058±0.004) mm,24 h失重率分别为19.93%和7.64%。无孔复合膜上的偏磷酸钙粒子分布均匀,细胞完全铺展,呈梭形;多孔复合膜上的偏磷酸钙粒子分布均匀,孔径分布也均匀,孔径2-8μm,细胞全完铺展,呈多边形,有多个触角,部分细胞触角进入支架内部。无孔与多孔复合膜上的细胞均表达CD105、CD90、CD44、CD29及CD73,组间细胞阳性率差异无显著性意义。实验制备的聚3-羟基丁酸-4-羟基丁酸/偏磷酸钙复合膜具有良好的细胞相容性,但无促细胞分化作用。     

Fabrication of NiFe2O4@carbon fiber coated with phytic acid-doped polyaniline composite and its application as an electromagnetic wave absorber

In this work, a novel CF@NiFe₂O₄ composite coated with phytic acid-doped polyaniline (CF@NiFe₂O₄@p-PANI) was facilely synthesized. First, a typical solvothermal reaction was applied to obtain the CF@NiFe₂O₄ composite, and then the phytic acid-doped polyaniline was grown in situ on the surface of the CF@NiFe₂O₄ composite. The morphological structure, chemical composition, and surface functional group distribution of this hybrid were systematically evaluated. The magnetic saturation (M_s) value of the hybrid is 29.9 emu g⁻¹, which represents an improvement in the magnetic loss. According to its reflection loss curve, the hybrid exhibits a superior EM wave absorption capacity, with a minimum reflection loss value and effective absorbing bandwidth of −46 dB when the sample thickness is 2.9 mm, and an effective absorption bandwidth of 5 GHz when the sample thickness is 1.5 mm. The excellent performance of this hybrid can mainly be attributed to its ideal matching of magnetic loss and dielectric loss, interfacial polarizations, eddy current loss and interface relaxation. This new material has the potential to be a superior electromagnetic wave absorber or applied as a functional filler to modify resin matrices.

A novel CF@NiFe₂O₄@p-PANI hybrid was designed. Phytic acid-doped polyaniline was applied in the synthesis of an EM wave absorber. The hybrid exhibits excellent EM wave-absorbing performance.     

Effect of tourmaline nanoparticles on the anticoagulation and cytotoxicity of poly(l-lactide-co-caprolactone) electrospun fibrous membranes

Tourmaline nanoparticles (TM NPs) were well dispersed in poly(l-lactide-co-caprolactone) (PLCL) fibers via electrospinning without a dispersant. Through the modification of TM NPs, the hydrophilicity and anticoagulant property of the composite electrospun fibrous membranes were improved. Compared with the PLCL membranes, the curve of dynamic clotting time in contact with the composite TM NPs/PLCL membranes descended more slowly. Particularly, the coagulation time of 8 wt% TM NPs/PLCL membrane was longer than 70 min, which was 174% higher than that of the PLCL membrane. At the same time, the cell compatibility and mechanical properties of TM NPs/PLCL membranes were analyzed. The cytotoxicity test showed that the grade of 8 wt% TM NPs/PLCL membrane was 0. The stretching experiments showed that the tensile strength of 8 wt% TM NPs/PLCL membrane (6.71 ± 0.30 MPa) was 267.33% higher than that of the PLCL membrane, and its elongation at break (141.83 ± 5.82%) was higher than the requirement of the coronary artery. These results indicated that the PLCL electrospun fibrous membranes modified with TM NPs have potential to be used in tissue engineering as small-caliber vascular grafts.

The hydrophilicity and anticoagulation of PLCL electrospun membranes were enhanced by the modification of well-dispersed TM NPs.     

Enhancement of rotator cuff tendon–bone healing using combined aligned electrospun fibrous membranes and kartogenin

Rotator cuff tear (RCT) is a major challenging shoulder disease because the fibrocartilage zone is hard to regenerate in the enthesis. Electrospun membranes with aligned nanofibers can guide the ordered tissue regeneration and kartogenin (KGN) is able to stimulate chondrocyte differentiation of mesenchymal stem cells. In this study, we fabricated a functional engineered scaffold for regenerating tendon–bone enthesis in RCTs by taking advantage of both the structural guiding ability of aligned nanofibers and the biology effects of KGN. Polycaprolactone (PCL) fibrous membranes with aligned nanofibers loaded with or without KGN were fabricated using electrospinning and characterized using scanning electron microscopy (SEM). The release of KGN from PCL membranes and the effects of KGN on differentiation of mesenchymal stem cells were investigated. Results indicated that 100 μM KGN-loaded PCL (KGN-PCL) membranes significantly stimulated chondrogenic and tenogenic differentiation of rat bone marrow stromal cells. In addition, after PCL and 100 μM KGN-PCL membranes were applied to an acute rat RCT model, KGN-PCL membranes promoted fibrocartilage formation and collagen organization as well as increased cross-sectional area and load failure. In conclusion, PCL electrospun fibrous membranes with aligned nanofibers and KGN could be an effective tissue engineering scaffold to enhance tendon–bone healing in RCTs.

Aligned PCL scaffolds loaded with an adequate amount KGN (KGN-PCL) could enhance tendon–bone healing enthesis in rotator cuff tears.     

聚碳酸亚丙酯/壳聚糖纳米纤维复合三维多孔支架的构建与性能

背景:聚碳酸亚丙酯(PPC)具有良好的力学性能和生物相容性,但是也存在合成高分子的共性不足即缺乏生物活性.壳聚糖纳米纤维具有优异的生物活性,但力学性能较差,很难保持稳定的高强度三维结构.目的:将壳聚糖纳米纤维与聚碳酸亚丙酯复合,制备具有优异生物活性和良好力学性能的三维多孔组织工程支架.方法:用溶液浇铸/粒子沥滤法制备PPC多孔支架,再用相分离法原位复合三维壳聚糖纳米纤维制备聚碳酸亚丙酯,壳聚糖纳米纤维复合三维多孔支架(PPC/CSNF).用扫描电子显微镜观察PPC及PPC,CSNF多孔支架微观形态,并测定其压缩模量、孔隙率.用扫描电子显微镜观察PPC/CSNF多孔支架在新西兰大白兔大腿皮下埋植1,2个月后的细胞生长情况.结果:PPC多孔支架孔径分布为200-500 μm且孔连通性好,PPC/CSNF多孔支架中的壳聚糖纳米纤维分布均匀其直径在50～500 nm之间;各种质量浓度的支架孔隙率均为90%以上;各种支架的压缩模量随着PPC浓度的增加而增加,最高可达约15 MPa;体内埋植的实验结果表明PPC/CSNF多孔支架具有良好的生物活性,可促进骨髓基质干细胞向软骨细胞分化.结果提示溶液浇铸/粒子沥滤法与低温相分离法相结合成功制备了力学性能与生物活性优异的PPC/CSNF多孔支架.该支架可促进新西兰大白兔的骨髓基质干细胞向软骨细胞分化.     

Synthesis and gas transport properties of polyamide membranes containing PDMS groups

A series of gas-separation polyamide-poly(dimethylsiloxane) (PA-PDMS) membranes containing PDMS groups were synthesized through the polycondensation reaction. The structural characteristics of polymers were evaluated by ¹H-NMR spectroscopy (NMR), Fourier-transform infrared spectroscopy (FTIR) and UV-vis absorption spectroscopy. The permeability and selectivity behavior was studied at different temperatures (25–55 °C) and pressures (1.0–3.0 atm), using various gases, such as H₂, O₂, CO₂, CH₄, and N₂. The effect of chemical structure, PDMS content, operating pressure and temperature on gas permeability was explored and discussed. Gas-permeation measurements showed that polyamides containing PDMS groups exhibited different separation performance. The PA-PDMS-20 membrane with 20 wt% PDMS exhibited the highest selectivity (CO₂/N₂ = 41.84 and O₂/N₂ = 7.01) at 35 °C and 3.0 atm while CO₂ and O₂ permeability was 29.29 barrer and 4.91 barrer, respectively.

PA-PDMS membranes were synthesized by polycondensation reaction and the gas permeability was found to increase with an increase of PPG content, with the gas permeability of PA-PDMS-20 membrane reaching 29.29 at 35 °C and 3.0 atm.     

Diffusivity and free anion concentration of ionic liquid composite polybenzimidazole membranes

In this article, PBI composite membranes containing the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-NTf₂) at 1, 5, 10, 20 and 50 wt% (named PBI-IL-x) have been prepared by a casting method. The internal morphology of the membranes was analyzed by scanning electron microscopy (SEM), revealing that the incorporation of IL promotes the formation of porous channels. Thermal and mechanical stability was confirmed by thermogravimetric analysis (TGA) and tensile test measurements. The ionic transport through membranes was analysed by means of electrochemical impedance spectroscopy (EIS), showing a dependence on the IL loading, reaching a highest conductivity value of 1.8 × 10⁻² S cm⁻¹ for the PBI-IL-50 membrane at 160 °C. The experimental results showed a Vogel–Fulcher–Tammann (VFT) type relation for the ionic conductivity with temperature and the calculated activation energies suggest that ionic conduction in the films can occur by both hopping and vehicle-type mechanisms. Eyring''s absolute rate theory was also used to obtain activation enthalpy and entropy from the temperature dependence of the conductivity. Diffusivity and free ion number density were obtained by means of electrode polarization analysis to obtain more insight into the conduction in these composite membranes. Finally, the Debye length was calculated and related to both transport parameters.

PBI composite membranes containing 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-NTf₂) at 1, 5, 10, 20 and 50 wt% have been prepared and the conductivity has been analyzed by electrochemical impedance spectroscopy.