Self-Assembly Molecularly Imprinted Nanofiber for 4-HA Recognition

In this paper, we provided a self-assembly strategy to prepare surface molecularly imprinted polyaniline (PANI) nanofiber. The route provides simplicity, convenience, low cost, and high-productivity due to the omission of the template guided materials and their post-treatment. The molecularly imprinted PANI nanofibers could selectively bind the template (4-hydroxybenzoic acid) molecules, and the nanofibers have large adsorption capacity and fast uptake kinetics for target species. The PANI nanofibers could provide a good material for imprinting various organic or biological molecules toward applications in chemical/biological sensors and bioassay.     

Electrostatic effects on nanofiber formation of self-assembling peptide amphiphiles

Self-assembling peptide amphiphile molecules have been of interest to various tissue engineering studies. These molecules self-assemble into nanofibers which organize into three-dimensional networks to form hydrocolloid systems mimicking the extracellular matrix. The formation of nanofibers is affected by the electrostatic interactions among the peptides. In this work, we studied the effect of charged groups on the peptides on nanofiber formation. The self-assembly process was studied by pH and zeta potential measurements, FT-IR, circular dichroism, rheology, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. The aggregation of the peptides was triggered upon neutralization of the charged residues by pH change or addition of electrolyte or biomacromolecules. Understanding the controlled formation of the hydrocolloid gels composed of peptide amphiphile nanofibers can lead us to develop in situ gel forming bioactive collagen mimetic nanofibers for various tissue engineering studies including bioactive surface coatings.     

基于荧光素的荧光纳米纤维的制备与表征

以电纺聚丙烯腈(PAN)纳米纤维为起始物, 经乙二胺改性后, 再利用Mannich反应将荧光素共价连接于PAN纳米纤维薄膜表面. 用荧光光谱、 扫描电镜和红外光谱进行了结构表征. 结果表明, 利用荧光素对静电纺丝薄膜表面进行修饰, 获得了很强的荧光信号, 证明了方法的可行性.     

The intrinsic nanofibrillar morphology of polyaniline

Polyaniline nanofibers are shown to form spontaneously during the chemical oxidative polymerization of aniline. The nanofibrillar morphology does not require any template or surfactant, and appears to be intrinsic to polyaniline synthesized in water. Two approaches--interfacial polymerization and rapidly-mixed reactions--have been developed to prepare pure nanofibers. The key is suppressing the secondary growth that leads to agglomerated particles. The effects of different dopant acids and solvents are discussed. Changing the dopant acid can be used to tune the diameters of the nanofibers between about 30 and 120 nm. Changing the organic solvent in interfacial polymerization reactions has little effect on the product. A brief discussion of the processibility of the nanofibers is presented. The possibility of creating nanofibrillar structures for selected polyaniline derivatives is also demonstrated.     

静电纺丝技术制备无机纳米纤维材料的应用

高压静电纺丝技术是一种简单通用的制备聚合物及无机纳米纤维材料的方法. 本文综述了利用高压静电纺丝技术制备的无机纳米纤维材料在能源、 纳电子器件、 催化以及传感器等领域的研究进展, 并对其发展前景进行了展望.     

Nanomechanical stimulus accelerates and directs the self-assembly of silk-elastin-like nanofibers

One-dimensional nanostructures are ideal building blocks for functional nanoscale assembly. Peptide-based nanofibers have great potential in building smart hierarchical structures due to their tunable structures at the single residue level and their ability to reconfigure themselves in response to environmental stimuli. We observed that pre-adsorbed silk-elastin-based protein polymers self-assemble into nanofibers through conformational changes on a mica substrate. Furthermore, we demonstrate that the rate of self-assembly was significantly enhanced by applying a nanomechanical stimulus using atomic force microscopy. The orientation of the newly grown nanofibers was mostly perpendicular to the scanning direction, implying that the new fiber assembly was locally activated with directional control. Our method provides a novel way to prepare nanofiber patterned substrates using a bottom-up approach.     

Characterizing zeta potential of functional nanofibers in a microfluidic device

The measurement of surface charge on nanofibers was achieved by characterizing zeta potential of the nanofibers via a newly developed device for streaming current measurement. Low flow rates were sufficient to generate detectable streaming currents in the absence of an externally applied voltage without damaging nanofiber samples. Zeta potential was calculated by using the Helmholtz-Smoluchowski equation and the measured streaming currents. Two acrylic plates were machined and assembled to form a microfluidic channel that is 150 μm high, 2.0mm wide, and 30 mm long. Two electrodes for the measurement of streaming currents were housed in the top plate. Two nanofibers of pure polyacrylonitrile (PAN) fibers and charged (TiO(2) incorporated) PAN fibers were prepared and characterized in the device. Monobasic sodium phosphate and dibasic sodium phosphate were used to prepare four different pH buffer solutions ranging from pH 5 to pH 8 in order to characterize the zeta potentials. The pure PAN nanofibers had negatively-charged surfaces regardless of pH. However, the zeta potentials of PAN/TiO(2) nanofibers changed from positive to negative at pH 6.5. The zeta potential measurements made on the nanofibers in this new microfluidic device matched with those of the powdered raw materials using a commercial Zetasizer.     

静电纺丝制备有机盐类非线性光学材料纳米纤维

采用静电纺丝技术制备的有机非线性光学材料纳米纤维可有效控制非线性光学材料的分子取向,其生色团可实现与有机单晶类似的优化排列结构,表现出了与纯生色团分子相近的宏观二阶非线性光学性质。 本文将有机盐类非线性光学材料掺杂在聚乙烯吡咯烷酮中制备出了具有各向异性结构且表面光滑、排列有序的纳米纤维薄膜,Kurtz非线性测试结果表明,随着薄膜厚度增加,其二次谐波信号强度成正比增大。     

Dynamic interaction between the growing Ca–P minerals and bacterial cellulose nanofibers during early biomineralization process

Bone is a composite of organic phase (collagen nanofibers) and Ca–P minerals (hydroxylapatite) and an important biological structure in the field of biomineralization, but the interaction between organic matrixes and inorganic minerals is still too ambiguous. In order to investigate the interaction between the growing Ca–P minerals and organic nanofibers during early biomineralization process, bacterial cellulose (BC) nanofibers were used as templates to mimic collagen nanofibers for Ca–P minerals deposition via biomineralization for periods from as short as 4–72 h. Our findings pointed out that the resultant Ca–P minerals formed on BC nanofibers were platelet-like calcium-deficient HAp which was analogous to those in natural bone tissue. Strikingly, we found that the growth of Ca–P minerals had influence on the structure and properties of BC nano-templates during biomineralization process.     

聚合物的静电纺丝

静电纺丝法是聚合物溶液或熔体在静电作用下进行喷射拉伸而获得纳米级纤维的纺丝方法.由纳米纤维制得的无纺布,具有孔隙率高、比表面积大、纤维精细程度与均一性高、长径比大等优点,从而赋予了静电纺丝纤维广泛的应用前景,它已在国内外引起了广泛的关注.本文介绍了静电纺丝的装置、基本原理及静电纺丝制备纳米纤维的研究进展,同时也叙述了其在各个领域的应用,最后展望了静电纺丝制备纳米纤维的发展方向及前景.     

Preparation and study of PPV/PVA nanofibers via electrospinning PPV precursor alcohol solution

We have found a simple method to prepare poly(phenylene vinylene) (PPV) nanofibers via electrospinning PPV precursor alcohol solution under annealed at 180 °C in a N₂ atmosphere. The nanofibers are uniform in diameter and long in decimeter magnitudes with resistance in decay, which makes them have potential applications in optical and electronic devices. The morphology can be better controlled by blend PPV precursor solution with poly(vinylalcohol) (PVA) aqueous solution. The fluorescence spectrum of PPV/PVA nanofibers exhibited appreciable blue shift, which made it possible to fabricate nanofibers with fluorescence from yellow-green to blue.     

Collagen nanofiber-covered porous biodegradable carboxymethyl chitosan microcarriers for tissue engineering cartilage

Nanofibrous collagen-coated porous carboxymethyl chitosan microcarriers (CMC-MCs) were successfully fabricated for use as injectable cell microcarriers. A modified phase separation method combined with temperature controlled freeze-extraction was used for formulating the CMC-MCs. Collagen nanofibers were immobilized onto the surfaces of the CMC-MCs via covalently anchoring some collagen molecules first and more molecules self-assembling into nano-scale fibrous networks afterward. Scanning electron microscopy and hydroxyproline colorimetry analysis revealed that more collagen was immobilized on the CMC-MCs with collagen molecules anchored initially. In vitro cell culture revealed that chondrocytes could adhere, proliferate, and remain differentiated on the nanofiber-coated CMC-MCs. Optical microscopy and confocal laser scanning microscopy showed that chondrocytes grew to confluence on the CMC-MCs within 3 days post-seeding. Subsequently, several confluent CMC-MCs attached to each other, forming tissue-like aggregates after 7 days culture. The mRNA expression of type II collagen was much stronger in chondrocytes cultured on the nanofiber-coated CMC-MCs for 7 days than those cultured in 24-well plates or on CMC-MCs without initial treatment. These porous CMC-MCs could be utilized for cultivating cells and for application in cartilage tissue engineering as injectable scaffolds for cell delivery.     

Unlocking the potential of thiaheterohelicenes: chemical synthesis as the key

The possibility of combining the electronic properties of oligothiophenes with potential chiroptical properties has fueled research in the area of thiaheterohelicenes. Recent reports that these molecules also exhibit fascinating interactions with biologically important macromolecules place further emphasis on the need for new synthetic methods to access thiaheterohelicenes. This review highlights the synthetic methods currently being used to prepare thiaheterohelicenes and discusses the role that chemical synthesis plays in the exploration of the properties of these helically chiral molecules.     

The Cooperative Effect of Both Molecular and Supramolecular Chirality on Cell Adhesion

Although helical nanofibrous structures have great influence on cell adhesion, the role played by chiral molecules in these structures on cells behavior has usually been ignored. The chirality of helical nanofibers is inverted by the odd–even effect of methylene units from homochiral l ‐phenylalanine derivative during assembly. An increase in cell adhesion on left‐handed nanofibers and weak influence of cell behaviors on right‐handed nanofibers are observed, even though both were derived from l ‐phenylalanine derivatives. Weak and negative influences on cell behavior was also observed for left‐ and right‐handed nanofibers derived from d ‐phenylalanine, respectively. The effect on cell adhesion of single chiral molecules and helical nanofibers may be mutually offset.     

Blends of TiO2 nanoparticles and poly (N-isopropylacrylamide)-co-polystyrene nanofibers as a means to promote the biorecognition of an anticancer drug

The poly (N-isopropylacrylamide)-co-polystyrene (PNIPAM-co-PS) nanofibers have been fabricated by electrospinning, and the blends of PNIPAM-co-PS nanofibers with titanium dioxide (TiO(2)) nanoparticles have been characterized and utilized as the new nanocomposites to enhance the relevant detection sensitivity of biomolecular recognition of an anticancer drug daunorubicin. Our observations demonstrate that upon application of the nanoTiO(2)-PNIPAM-co-PS polymer nanocomposites, the drug molecules could be readily deposited on the surface of the relevant blends so that the remarkable enhancement effect of the new nanocomposites on the respective biorecognition of daunorubicin could be observed, suggesting the potential valuable application of the blending of the nanoTiO(2) and PNIPAM-co-PS polymer nanocomposites in high sensitive bioanalysis.     

Fabrication of photo‐cross‐linked polyethyleneimine‐based barriers for CO2 capture

In this study, first, polyethyleneimine was acrylated and mixed with polyvinyl alcohol solution to prepare photo‐crosslinked polyethyleneimine (PEI)‐based nanofibers by utilizing ultraviolet and electrospinning technique at the same time. For CO₂ permeability testing, same formulations were prepared by using solvent casting technique and exposed to ultraviolet light to have polyethyleneimine‐based membrane films. The chemical structures of the nanofibers were characterized by Fourier transform infrared spectroscopy. The thermal properties of nanofibers were examined by thermal gravimetric analysis and differential scanning calorimeter. The morphology of nanofibers was investigated by scanning electron microscopy. CO₂ permeabilities of samples were also measured. Copyright © 2015 John Wiley & Sons, Ltd.     

Nanofiber formation of hydroxylpropylcellulose (HPC)

The aggregative behaviors of hydroxypropylcellulose (HPC) molecules in aqueous solution and on substrates have been observed by employing laser light scattering (LLS) and, after deposition on a mica surface, atomic force microscopy (AFM). LLS studies showed that the HPC molecules formed large aggregates through self-association when the concentration of the solution was above the critical concentration c(t). AFM measurements revealed that when a dilute aqueous solution of HPC molecules was deposited onto a mica substrate at a temperature below its lower critical solution temperature (LCST) thin nanofibers were formed with a height of 0.9 nm, whereas thick nanofibers were formed when an aqueous solution of HPC molecules was deposited onto a substrate above its LCST. Furthermore, the growth of nanofibers led to the formation of fan structures.     

TGA analysis of polypropylene-carbon nanofibers composites

TGA investigations on the thermal degradation of isotactic polypropylene-vapor grown carbon nanofibers composites in nitrogen are reported. The mass evolution as a function of temperature is a single sigmoid for both polypropylene and polypropylene loaded with carbon nanofibers. The inflection temperature of these sigmoids increases as the concentration of carbon nanofibers is increased. The width of the degradation process narrows as the concentration of carbon nanofibers is increased due to a better homogenization of the local temperature provided by the high thermal conductivity of carbon nanofibers. Thermogravimetric analysis data indicate the formation of polymer-carbon nanofiber interface. Based on TGA data, a two-layer structure is proposed for carbon nanofibers-polypropylene interface. The external layer is soft and has a thickness of about 10² nm that confines most polymer molecules in interaction with nanofibers. The core layer is rigid and has a thickness of the order of few nanometers.     

生物活性胶原蛋白及明胶形态的表征研究

采用弱酸处理法,从新鲜牛皮中提取了胶原蛋白,通过与明胶对比,采用CD、AFM、FTIR和荧光方法对其结构形态进行了表征研究。结果表明,所提取胶原蛋白保持了固有的生物活性,具有典型的α-螺旋结构。首次建立了稳态荧光的表征方法,不仅与其他方法具有重要互补性,而且具有准确、灵敏、快捷的特点,是表征、研究胶原蛋白及其变性/复性行为的有效手段。     

纳米碳纤维负载钯催化剂在Heck反应中的应用——载体相互作用的影响

使用多元醇还原法制备了均匀分散的钯纳米颗粒.将钯纳米颗粒负载于板式、鱼骨式和管式纳米碳纤维,得到稳定、可重复使用的非均相催化剂.实验结果表明,钯纳米胶粒同载体之间的电位差对钯在载体上的负载量、粒子大小以及Heck反应中钯的溶失量有很大的影响.在制备过程中,增加钯纳米胶粒同纳米碳纤维表面的电位差能够大大降低钯在Heck反应中的流失.催化剂的反应活性随钯粒子的增大而降低.