Synthesis of fluorescent PVA/polypyrrole-ZnO nanofibers

Electro spinning is a simple and efficient technique to produce polymer nanofibers. Here, we describe the preparation of electrospun PVA/PPy–ZnO fluorescent fibers and discuss their characterization by use of UV–Vis and Fourier transform infrared spectroscopies, and fluorescence and scanning electron microscopies. These hybrid organic–inorganic fibers exhibit a visible emission of 526 nm with a well-defined green color, as the ZnO–NPs fluorescence emission at 390 nm is quenched. The scanning electronic microscopy images reveal that the fibers present an average diameter of 324 nm and good surface quality. We have observed that their Ohmic behavior is light sensitive as the charge transport along the fibers is highly affected by UV illumination. Since this is a reversible effect, and a quick recovery of the electrical resistance original value occurs right after the incident UV light is turned off, we suggest that these organic–inorganic materials can find useful applications in the preparation of various polymer-based micro and nano optoelectronic devices, such as low-cost flexible photovoltaic devices and UV sensors.     

Mechanical properties of electrospun PVA/MWNTs composite nanofibers

Composites of polyvinyl alcohol (PVA) and multi-walled carbon nanotubes (MWNTs) were prepared by electrospinning. A PVA/MWNTs solution was electrostatically spun to form filler wrapped nanofibers, with a diameter of ∼ 100-200 nm. As the concentration of filler in the composite was varied, the coloration of the fiber sheets changed. The SEM and TEM analyses of the fiber sheets revealed that the deformation of the fiber increases with increasing nanotube concentration. The mechanical properties were studied using a universal testing machine (UTM). The analysis is presented in detail. It is argued that the degree of dispersivity orientation and anisotropy of the nanotubes and the amount of interfacial stress in the filler/polymer are the predominant factors determining the variation in the tensile properties of the composites with the filler concentration.     

Evaluation of proanthocyanidin-crosslinked electrospun gelatin nanofibers for drug delivering system

Electrospun nanofibers are excellent candidates for various biomedical applications. We successfully fabricated proanthocyanidin‐crosslinked gelatin electrospun nanofibers. Proanthocyanidin, a low cytotoxic collagen crosslinking reagent, increased the gelatin crosslinking percentage in the nanofibers from 53% to 64%. The addition of proanthocyanidin kept the nanofibers from swelling, and, thus, made the fibers more stable in the aqueous state. The compatibility and the release behavior of the drug in the nanofibers were examined using magnesium ascorbyl phosphate as the model drug. Proanthocyanidin also promoted drug loading and kept the drug release rate constant. These properties make the proanthocyanidin‐crosslinked gelatin nanofibers an excellent material for drug delivery. In the cell culture study, L929 fibroblast cells had a significantly higher proliferation rate when cultured with the gelatin/proanthocyanidin blended nanofibers. This characteristic showed that proanthocyanidin‐crosslinked gelatin electrospun nanofibers could potentially be employed as a wound healing material by increasing cell spreading and proliferation.     

含纳米银的明胶/壳聚糖纳米纤维的制备及其抗菌性能研究

以浓度为88%的甲酸溶液作为纺丝溶剂,采用静电纺丝和紫外光照射还原的方法制备了含纳米银颗粒的明胶/壳聚糖纳米纤维。研究发现,壳聚糖的加入量低于明胶质量的3/16时可以得到纳米纤维,纤维平均直径随着硝酸银加入量的增大而减小,纤维表面纳米银的平均直径随着硝酸银加入量的增大而增大,在纺丝体系中硝酸银的加入量存在一个极限值。所制得含纳米银的明胶/壳聚糖纳米纤维对金黄色葡萄球菌和绿脓杆菌具有较好的抑菌性能,纺丝时加入1%硝酸银制得纳米纤维膜的抑菌率达到99%以上,这种抗菌型纳米纤维可以应用于医用敷料等领域。     

Synthesis and morphology of electrospun PVA/PLZT composite and single phase PLZT nanofibers

Polyvinyl alcohol/lead lanthanum zirconate titanate (PVA/PLZT) composite nanofibers were prepared by the electrospinning method. The PLZT sol was prepared by using lead acetate trihydrate, titanium isopropoxide and zirconium propoxide molecular precursors based on sol-gel procedure. The influence of applied voltage, flow rate and needle-to-collector distance on the composite fiber morphology and diameters has been studied. The nanofibers were characterized by X-ray diffraction, TGA-DSC, FTIR spectroscopy and scanning electron microscopy (SEM). Single phase with perovskite structures PLZT nanofibers were also obtained by calcining the PVA/PLZT nanofibrous mat at 650 °C for 2 h. A linear correlation was observed between the single perovskite phase evolution and the calcination temperature.     

Electrospinning of PLGA/gelatin randomly-oriented and aligned nanofibers as potential scaffold in tissue engineering

Electrospinning technique can be used to produce the three-dimensional nanofibrous scaffold similar to natural extracellular matrix, which satisfies particular requirements of tissue engineering scaffold. Randomly-oriented and aligned poly(lactic-co-glycolic acid) (PLGA) and PLGA/gelatin biocomposite scaffolds were successfully produced by electrospinning in the present study. The resulting nanofibrous scaffolds exhibited smooth surface and high porous structure. Blending PLGA with gelatin enhanced the hydrophilicity but decreased the average fiber diameter and the mechanical properties of the scaffolds under the same electrospinning condition. The cell culture results showed that the elongation of the osteoblast on the aligned nanofibrous scaffold was parallel to the fiber arrangement and the cell number was similar to that of randomly-oriented scaffold, indicating that the aligned nanofibrous scaffold provide a beneficial approach for the bone regeneration.     

Electrospinning of porphyrin/polyvinyl alcohol (PVA) nanofibers and their acid vapor sensing capability

Fluorescing 5,10,15,20-terakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP)-embedded and -coated polyvinyl alcohol (PVA) nanofibers were fabricated by using the electrospinning technique. To improve nonpolar solvent solubility of TMPyP/PVA nanofibers, tetraethyl orthosilicate (TEOS) was used as a cross-linking agent. UV-vis spectroscopy showed a strong Q band and two relatively weak Soret bands from the TMPyP/PVA nanofibers, and revealed that the TMPyP molecules were homogeneously loaded to the fibers. Scanning electron microscopy revealed that the electrospun nanofibers had ultrafine structures with an average diameter of ca. 250 nm. X-ray photoelectron spectroscopy confirmed the compositional structure of TMPyP/PVA/TEOS nanofibers and revealed the relative coverage of TMPyP molecules on the surface of TMPyP-embedded and TMPyP-coated PVA/TEOS fibers. For the comparison of the acid vapor sensitivity, TMPyP-embedded PVA/TEOS films, and TMPyP-embedded PVA/TEOS fibers, TMPyP-coated PVA/TEOS fibers were exposed to 1N nitric-acid vapor for 20-60 seconds. Fluorescence microscopy revealed that TMPyP-coated PVA/TEOS nanofibers exhibited better acid-sensing capability than TMPyP-embedded PVA/TEOS nanofibers and films.     

Preparation of Fe3O4/PVA nanofibers via combining in-situ composite with electrospinning

A novel approach, combining in-situ composite method with electrospinning, was used to prepare high magnetic Fe₃O₄/poly(vinyl alcohol) (PVA) composite nanofibers. Fe₃O₄ magnetic fluids were synthesized by chemical co-precipitation method in the presence of 6 wt.% PVA aqueous solution. PVA was used as stabilizer and polymeric matrix. The resulting Fe₃O₄/PVA composite nanofibers were characterized with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffractometer (XRD), respectively. These composite fibers showed a uniform and continuous morphology, with the Fe₃O₄ nanoparticles embedded in the fibers. Magnetization test confirmed that the composite fiber showed a high saturated magnetization (M_s = 2.42 emµ·g^-1) although only 4 wt.% content.     

Fabrication of mineralized electrospun PLGA and PLGA/gelatin nanofibers and their potential in bone tissue engineering

Surface mineralization is an effective method to produce calcium phosphate apatite coating on the surface of bone tissue scaffold which could create an osteophilic environment similar to the natural extracellular matrix for bone cells. In this study, we prepared mineralized poly(d,l-lactide-co-glycolide) (PLGA) and PLGA/gelatin electrospun nanofibers via depositing calcium phosphate apatite coating on the surface of these nanofibers to fabricate bone tissue engineering scaffolds by concentrated simulated body fluid method, supersaturated calcification solution method and alternate soaking method. The apatite products were characterized by the scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), and X-ray diffractometry (XRD) methods. A large amount of calcium phosphate apatite composed of dicalcium phosphate dihydrate (DCPD), hydroxyapatite (HA) and octacalcium phosphate (OCP) was deposited on the surface of resulting nanofibers in short times via three mineralizing methods. A larger amount of calcium phosphate was deposited on the surface of PLGA/gelatin nanofibers rather than PLGA nanofibers because gelatin acted as nucleation center for the formation of calcium phosphate. The cell culture experiments revealed that the difference of morphology and components of calcium phosphate apatite did not show much influence on the cell adhesion, proliferation and activity.     

Emulsion electrospun nanofibers as substrates for cardiomyogenic differentiation of mesenchymal stem cells

The potential of cardiomyogenic differentiation of human mesenchymal stem cells (hMSCs) on emulsion electrospun scaffold containing poly(l-lactic acid)-co-poly-(ε-caprolactone), gelatin and vascular endothelial growth factor (PLCL/GV) was investigated in this study. The characterizations of the scaffold were carried out using scanning electron microscope (SEM), transmission electron microscope, water contact angle and porometer. The proliferation of hMSCs showed that 73.4 % higher cell proliferation on PLCL/GV scaffolds than that on PLCL scaffold after 20 days of cell culture. Results of 5-chloromethylfluorescein diacetate staining and SEM morphology analysis indicated that hMSCs differentiated on PLCL/GV scaffolds showed irregular morphology of cardiomyocyte phenotype compared to the typical long and thin hMSC phenotype. Immunostaining results showed the expression of alpha actinin and myosin heavy chain. Our studies identified emulsion electrospinning as a method for fabrication of core–shell fibers suitable for the differentiation of stem cells to cardiac cells, with potential application in cardiac regeneration.     

壳聚糖/聚乙烯醇共混膜用于草莓保鲜的研究

采用溶液浇筑法制备了壳聚糖/聚乙烯醇共混膜.通过红外光谱,机械性能测试,透气透湿率测试,抑菌性能测试等表征了共混膜的性能.通过保鲜实验,发现含20％壳聚糖的共混膜已具有良好的保鲜性能,可以大大延长草莓的保存期限.     

Chemical-assisted bonding of thermoplastics/elastomer for fabricating microfluidic valves

Thermoplastics such as cyclic olefin copolymer (COC) and polymethylmethacrylate (PMMA) have been increasingly used in fabricating microfluidic devices. However, the state-of-the-art microvalve technology is a polydimethylsiloxane (PDMS)-based three-layer structure. In order to integrate such a valve with a thermoplastics-based microfluidic device, a bonding method for thermoplastics/PDMS must be developed. We report here a method to bond COC with PDMS through surface activation by corona discharge, surface modification using 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), and thermal annealing. The method is also applicable to PMMA. The bonding strength between thermoplastics and PDMS was represented by the peeling force, which was measured using a method established by the International Organization for Standardization (ISO). The bonding strength measurement offered an objective and quantitative indicator for protocol optimization, as well as comparison with other PDMS-associated bonding methods. Using optimized bonding conditions, two valve arrays were fabricated in a COC/PDMS/COC device and cyclic operations of valve closing/opening were successfully demonstrated. The valve-containing devices withstood 100 psi (～689 KPa) without delamination. Further, we integrated such valve arrays in a device for protein separation and demonstrated isoelectric focusing in the presence of valves.     

改性纳米SiO_2/PVA复合纤维的制备及重金属离子吸附性能

通过静电纺丝技术制备酰肟化功能改性的纳米SiO_2/聚乙烯醇(SiO_2/PVA)复合纤维膜。采用SEM、FTIR、DSC和TGA进行表征分析;考察了在水溶液中随pH值和接触时间的变化纤维膜对金属离子吸附效果的影响。研究表明,在pH=6的条件下,纳米纤维对金属离子的吸附最佳,对Cu2+、Ni 2+金属离子的最大吸附量分别为143.7mg/g和125.1mg/g,平衡吸附时间为240min。在纤维膜吸附的前50min内,SiO_2/PVA纤维膜对Cu2+和Ni 2+金属离子的吸附量为126.8mg/g和109.8mg/g,吸附率分别为90.18%和89.92%。通过吸附等温线和吸附方程考察SiO_2/PVA纤维对Cu2+和Ni 2+金属离子的吸附行为。结果显示,复合纤维对两种金属离子的吸附满足拟二级动力学方程,热力学分析表明,吸附过程符合Langmuir单层吸附。使用酸处理纤维膜进行再生吸附试验,发现循环4次试验后,吸附效率达到53%,结果说明复合纤维膜可作为可再生金属离子吸附材料。     

Preparation and luminescence properties of La6MoO12:Eu3+/PVA nanofibers by Pechini/electrospinning process

The 20% concentration Eu3+-based red-emitting phosphor, nano-sized La6MoO12:Eu3+ was prepared by the Pechini method. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), photoluminescence (PL), and decay curves were used to characterize the resulting samples. The phosphor can be efficiently excited by near UV light and exhibits an intense red luminescence corresponding to the electric dipole transition 5D0 --> 7F2 at 615 nm. When the phosphor was mixed into poly(vinyl alcohol) aqueous solution, the fluorescent nanofibers could be prepared by electrospinning process. It was suggested that the La6MoO12:Eu3+ phosphor would be a promising red component for solid-state lighting devices based on InGaN or GaN light-emitting diodes.     

Effects of different types of PVA on the properties of the nano-TiO2/PVA

用硅烷偶联剂γ-甲基丙烯酰氧基丙基三甲氧基硅烷（KH550）对纳米TiO2进行改性,将不同比例的聚乙烯醇（17-88与17-99）相混合制成胶液,再采用直接共混法制备了纳米TiO2/聚乙烯醇（PVA）复合材料,并流延成膜。通过自制透水仪、扫描电镜、热失重分析、拉伸强度、耐水性能以及透明性对纳米TiO2/PVA复合膜进行表征,探讨不同含量的PVA 17-88对复合膜的性能影响。结果表明,PVA 17-88的质量分数为30%,纳米TiO2/PVA膜厚度控制在25～30μm,透水量较大,拉伸强度达到28.72MPa,耐水性能最佳。     

PVA/PVP/Ag+共混膜渗透汽化分离苯/环己烷混合物

PV/PVP/Ag+膜在苯、环己烷混合物中的溶胀实验发现,膜优先吸附苯,且膜中Ag+含量越大,膜在苯中的溶胀率越大,在环己烷中溶胀率越小.渗透汽化测试结果也表明,PVA/PVP/Ag+膜对苯/环己烷的分离性能明显优于PVA/PVP膜.而且,随着膜中Ag+含量的增加,膜的渗透通量J增大;分离因子先增大后减小,当膜中w(聚合物)∶w(AgNO3)＝1∶1时,分离因子α达到最大值,为47.5,通量为7.8 g/(m2*h)(进料的质量分数为10%,20 ℃).而对膜进行交联改性后,分离因子可进一步提高,但通量下降.     

"Click chemistry" in the preparation of porous polymer-based particulate stationary phases for mu-HPLC separation of peptides and proteins

With the use of the copper(I)-catalyzed (3 + 2) azide-alkyne cycloaddition, an element of "click chemistry," stationary phases carrying long alkyl chains or soybean trypsin inhibitor have been prepared for use in HPLC separations in the reversed-phase and affinity modes, respectively. The ligands were attached via a triazole ring to size monodisperse porous beads containing either alkyne or azide pendant functionalities. Alkyne-containing beads prepared by direct copolymerization of propargyl acrylate with ethylene dimethacrylate were allowed to react with azidooctadecane to give a reversed-phase sorbent. Azide-functionalized beads were prepared by chemical modification of glycidyl methacrylate particles. Subsequent reaction with a terminal aliphatic alkyne produced a reversed-phase sorbent similar to that obtained from the alkyne beads. Soybean trypsin inhibitor was functionalized with N-(4-pentynoyloxy)succinimide to carry alkyne groups and then allowed to react with the azide-containing beads to produce an affinity sorbent for trypsin. The performance of these stationary phases was demonstrated with the HPLC separations of a variety of peptides and proteins.     

不同型号PVA对纳米TiO2/PVA复合材料性能的影响

用硅烷偶联剂γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH550)对纳米TiO₂进行改性, 将不同比例的聚乙烯醇(17-88与17-99)相混合制成胶液, 再采用直接共混法制备了纳米TiO₂/聚乙烯醇(PVA)复合材料, 并流延成膜。通过自制透水仪、 扫描电镜、 热失重分析、 拉伸强度、 耐水性能以及透明性对纳米TiO₂/PVA复合膜进行表征, 探讨不同含量的PVA 17-88对复合膜的性能影响。结果表明, PVA 17-88的质量分数为30%, 纳米TiO₂ /PVA膜厚度控制在25~30 μm, 透水量较大, 拉伸强度达到28.72 MPa, 耐水性能最佳。      

PVA/明胶/Fe_3O_4磁敏感性水凝胶的制备及性能研究

采用物理交联的方法制备了聚乙烯醇(PVA)/明胶/Fe3O4磁敏感性水凝胶。对Fe3O4磁敏感性水凝胶在加入明胶前后的力学性能及溶胀性能进行了对比分析,利用SEM、IR等对水凝胶进行表征,采用振动样品磁强计测试了其磁敏感性。结果表明,PVA/Fe3O4磁敏感性水凝胶加入明胶后,其力学性能明显增强,提高了0.4~0.7MPa,当磁性粒子含量为1.5%时,力学性能较好;加入明胶后,水凝胶脱水率和溶胀度都随着磁性粒子增加而增大;从SEM照片及IR图上可知,加入明胶后,PVA、明胶和Fe3O4三者相容性较好;测得的水凝胶磁敏感性较好。