Improved survival of cardiac cells on surface modified electrospun nanofibers

Polycaprolactone (PCL) is a popular synthetic polymer used in the field of cardiac tissue engineering (CTE) due to its non-toxic degraded by products and low cost manufacturing method. However, hydrophobic nature of this material limits its wide spread application in different cell interaction processes. Therefore, current study aims to chemically modify PCL made random and aligned nanofibers with collagen coating mimicking the oriented matrix of the cardiac cells. Morphological and chemical properties of the electrospun PCL nanofibers were evaluated by SEM, FTIR, XRD and water contact angle measurement. Results indicated that the anisotropic characteristics of aligned nanofibers promoted cell attachment and alignment, which closely match the requirements of native cardiac cells. Thus, aligned nanofibers could be preferred for cardiac tissue regeneration and defects over random nanofibers.     

Fabrication of random and aligned electrospun nanofibers containing graphene oxide for skeletal muscle cells scaffold

Graphene oxide (GO)‐based materials have been explored in biomedical applications as active engineered materials for diagnosis and therapy. Although a large number of studies have been carried out in the last years, aspects involving the orientation and elongation of cells on GO immobilized on polymeric nanofibers are still scarce. We investigated the interactions between skeletal muscle cells and GO immobilized on random and aligned electrospun nanofibers of poly(caprolactone) (PCL), a biocompatible and biodegradable polymer. Oxygen plasma was employed to modify the nanofiber polymer surface to enhance the interactions between the PCL fibers and GO. Scanning electron microscopy and confocal microscopy revealed the morphology and orientation of skeletal muscle cells (C2C12 cells) on random and aligned GO/PCL nanofibers. The approach employed here is useful to investigate the interaction of skeletal muscle cells with biocompatible polymer nanofibers modified with GO intended for cell scaffolds and tissue engineering.     

Electrospun nanofibrous polycaprolactone scaffolds for tissue engineering of annulus fibrosus

The annulus fibrosus comprises concentric lamellae that can be damaged due to intervertebral disc degeneration; to provide permanent repair of these acquired structural defects, one solution is to fabricate scaffolds that are designed to support the growth of annulus fibrosus cells. In this study, electrospun nanofibrous scaffolds of polycaprolactone are fabricated in random, aligned, and round-end configurations. Primary porcine annulus fibrosus cells are grown on the scaffolds and evaluated for attachment, proliferation, and production of extracellular matrix. The scaffold consisting of round-end nanofibers substantially outperforms the random and aligned scaffolds on cell adhesion; additionally, the scaffold with aligned nanofibers strongly affects the orientation of cells.     

Preparation and Properties of Electrospun Sheath-core Modified-PMMA Nanofibers with Photoluminescence and Photochromic Functions

Multi-functional nanofibers are playing an important role in the optical field, and are widely used in fluorescence indication, product anti-counterfeit identification and smart clothing. Nanofibers with photoluminescence and photochromic functions are already attracting more interest from researchers. In this work, based on electrospun technology, the modified-PMMA nanofibers[PMMA=poly(methyl methacrylate)] with photoluminescence and photochromic functions were prepared through the design of the sheath-core structure(SCNFs 1-4). Compared with other samples, SCNF-4 shows outstanding photoluminescence and photochromic functions. SCNF-4 can produce green light and its fluorescence intensity and fluorescence lifetime can reach 7144 a.u. and 1031.32 μs, respectively. In photochromic functions, SCNF-4 can show purple in 1 min under the 365 nm ultraviolet light, and the color can be preserved for more than 4 h under the sunlight. When SCNF-4 is irradiated by far infrared light, the color of the samples can fade quickly in 40 s. Under the irradiation of ultraviolet light of different wavelengths, SCNF-4 can display multi-color fluorescence and achieve a reversible transition between white and purple. The design of the sheath-core structure realizes the complementarity of photoluminescence and photochromic functions of the electrospun modified-PMMA nanofibers, which is important to promote the wide application of multi-functional nanofibers in the optical field.     

Dye,fluorophores and pigment coloration of nanofibers produced by electrospinning

Polymeric nanofibers produced by the electrospinning technique are widely used in industrial scale production. Nanofibers chiefly find applications in filtration media and active–barrier surfaces for medical, biological, and military applications. In such applications, the quantity and the uniformity of the nanofibers distribution play a leading role in the product characteristics. For this reason, there is considerable interest regarding the nanofibers recovering quantification and simplification of the qualitative analysis. With the aim to improve and simplify the nanofibers relevability, a coloration approach for nanofibers has been designed and tested. The coloration has been carried out by organic dyes, pigments, and organic fluorophores and the consequent nanofibers' color has been analyzed by optical analysis, colorimetry, and spectroscopy. The coloration obtained by different dyes has been compared and their effect on the nanofibers relevability has been investigated. Moreover, the leading role of the light scattering phenomenon on the nanofiber coloration efficacy has been investigated by comparing the coloration response of nanofibers and film samples on equal terms of dye content. The study has been carried out using polyamide‐6 (PA6) as the testing polymer but the recovering quantification, the coloration approach, and the interaction between light and nanofibers can be extended to all the electrospinnable polymers. Copyright © 2008 John Wiley & Sons, Ltd.     

White-Light-Emitting Self-Assembled NanoFibers and Their Evidence by Microspectroscopy of Individual Objects

The self-assembly of a blue-emitting light-harvesting organogelator and specifically designed highly fluorescent tetracenes yields nanofibers with tunable emissive properties. In particular, under near-UV excitation, white light emission is achieved in organogels and dry films of nanofibers. Confocal fluorescence microspectroscopy demonstrates that each individual nanofiber emits white light. A kinetic study shows that an energy transfer (ET) occurs between the blue-emitting anthracene derivative and the green- and red-emitting tetracenes, while inter-tetracene ETs also take place. Moreover, microscopy unravels that the nanofibers emit polarized emission in the blue spectral region, while at wavelengths higher than 500 nm the emission is not significantly polarized.     

Mechanical and shape memory performance of shape memory polyurethane-based aligned nanofibers

In recent years, shape memory polyurethane (SMPU) as a smart material has been used in various applications owing to its desirable shape memory effect and biocompatibility. In this study, unidirectional SMPU nanofibers are innovated by electrospinning to clarify the mechanical and shape memory properties with nanofiber directions. The results showed that when the nanofiber alignment degree is 0° (parallel to the tensile direction), the aligned SMPU nanofibers achieved the obvious improvement of tensile strength (increased to 135%) and elastic modulus (increased to 313%), compared with the random SMPU nanofiber. Moreover, the developed aligned nanofibers exhibited good ability against stress relaxation and creep under constant strain or constant stress conditions in cyclic loading. The aligned SMPU nanofibers with a 0° alignment degree exhibited excellent shape memory properties with shape recovery rates larger than 93% and shape fixity rates larger than 90%, and a dramatic increase of shape recovery stress.     

Formation of polyaniline nanofibers: a morphological study

Polyaniline (PANI) powders were prepared by solution precipitation, rapid mixing polymerization, and interfacial polymerization to find the key factors that influence the formation and growth of PANI nanofibers. In chemical oxidative polymerization of aniline, the morphology of the product is mainly determined by aniline concentration. In the case of lower aniline concentration, PANI nanofibers were formed and can be preserved and collected as final product, while in the case of higher aniline concentration, larger sized PANI particles or agglomerates were obtained owing to the growth of the nanofibers. Without participation of the oxidizing step, solid PANI samples with compact structures and dissimilar morphologies were achieved by random accumulation of PANI molecules.     

Electrospun aligned nanofibers: A review

Electrospinning (e-spinning) is famous for the construction and production of ultrafine and continuous micro-/nanofibers. Then, the alignment of electrospun (e-spun) nanofibers becomes one of the most valuable research topics. Because aligned fibers have more advantages over random fibers, such as better mechanical properties, faster charge transport, more regular spatial structure, etc. This review summarizes various electrospinning techniques of fabricating aligned e-spun nanofibers, such as early conventional methods, near-field e-spinning, and three-dimensional (3D) printing e-spinning. Among them, four auxiliary preparation methods (e.g., auxiliary solid template, auxiliary liquid, auxiliary electromagnetic field and auxiliary airflow), two collection modes (static and dynamic collection), and the controllability of near-field e-spinning and 3D printing e-spinning are highlighted. The representative applications depending on aligned nanofibers are classified and briefly introduced, emphasizing in the fields of 1D applications (e.g., field-effect transistor, nanochannel and guidance carrier), 2D applications (e.g., platform for gas detection, filter, and electrode materials storage), and 3D applications (e.g., bioengineering, supercapacitor, and nanogenerator). At last, the challenges and prospects are addressed.     

Preparation and Photocatalysis of Mesoporous TiO2 Nanofibers via an Electrospinning Technique

Mesoporous TiO₂ nanofibers have been synthesized by a new method that combines sol-gel chemistry and electrospinning technique. The obtained mesoporous TiO₂ nanofibers were characterized with scanning electron microscopy(SEM), X-ray diffraction(XRD), transmission electron microscopy(TEM) and nitrogen adsorption-desorption isotherms. The photocatalytic performance was evaluated by the photocatalytic degradation of Rhodamine B under UV light irradiation. The results show that mesoporous TiO₂ nanofibers exhibit higher photocatalytic activity compared with nonporous TiO₂ nanofibers.     

Poly(glycerol sebacate) nanofiber scaffolds by core/shell electrospinning

The novel biomaterial poly(glycerol sebacate) (PGS) holds great promise for tissue engineering and regenerative medicine. PGS is a rubbery, degradable polymer much like elastin; however, it has been limited to cast structures. This work reports on the formation of PGS nanofibers in random non-woven mats for use as tissue engineering scaffolds by coaxial core/shell electrospinning. PGS nanofibers are an inexpensive and synthetic material that mimics the chemical and mechanical environment provided by elastin fibers. Poly(lactide) was used as the shell material to constrain the PGS during the curing process and was removed before cell seeding. Human microvascular endothelial cells from skin (HDMEC) were used to evaluate the in-vitro cellular compatibility of the PGS nanofiber scaffolds. [Figure: see text].     

Fabrication and characterization of NiTiO3 nanofibers by sol–gel assisted electrospinning

Continuous NiTiO₃ nanofibers have been successfully synthesized by a sol–gel assisted electrospinning method followed by calcination at 600 °C in air. These nanofibers were characterized for the morphological, structural and optical properties by scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and UV–visible (UV–vis) diffuse reflectance spectroscopy (DRS). SEM results reveal that the obtained NiTiO₃ nanofibers are 175 nm in diameter and several micrometers in length after annealing at 600 °C. The XRD analysis shows that the nanofibers possess highly crystalline structure with no impurity phase. In contrast, the NiTiO₃ nanoparticles synthesized at the identical conditions by a sol–gel route have impurities including TiO₂ and NiO. Moreover, the electrospun NiTiO₃ nanofibers are endowed with an obvious optical absorbance in the visible range, demonstrating they have visible light photoresponse.     

An effective continuum approach for modeling non-equilibrium structural evolution of protein nanofiber networks

We quantify the formation and evolution of protein nanofibers using a new phase field modeling framework and compare the results to transmission electron microscopy measurements (TEM) and time-dependent growth measurements given in the literature. The modeling framework employs a set of effective continuum equations combined with underlying nanoscale forces and chemical potential relations governing protein nanofiber formation in solution. Calculations based on the theoretical framework are implemented numerically using a nonlinear finite element phase field modeling approach that couples homogenized protein molecular structure via a vector order parameter with chemical potential relations that describe interactions between the nanofibers and the surrounding solution. Homogenized, anisotropic molecular and chemical flux relations are found to be critical in obtaining nanofiber growth from seed particles or a random monomer bath. In addition, the model predicts both sigmoidal and first-order growth kinetics for protein nanofibers for unseeded and seeded models, respectively. These simulations include quantitative predictions on time scales of typical protein self-assembly behavior which qualitatively match TEM measurements of the RADA16-I protein and growth rate measurements for amyloid nanofibers from the literature. For comparisons with experiments, the numerical model performs multiple nanofiber protein evolution simulations with a characteristic length scale of ～2.4 nm and characteristic time scale of ～9.1 h. These results provide a new modeling tool that couples underlying monomer structure with self-assembling nanofiber behavior that is compatible with various external loadings and chemical environments.     

Fabrication and photocatalytic activity of LaFeO3 ribbon-like nanofibers

LaFeO₃ ribbon-like nanofibers were synthesized via a sol–gel-assisted electrospinning method. The differences in morphology and photocatalytic property of LaFeO₃ nanofibers prepared through different needles were investigated. At the same time, the morphology and photocatalytic activity of porous LaFeO₃ nanobelts formed at different calcination temperatures were also investigated. Scanning electron microscopy results revealed that the obtained ribbon-like LaFeO₃ nanofibers made using a coaxial needle contained a large number of pores. Moreover, with the increase of calcination temperature, the morphology of the fibers also changed. X-ray diffraction analysis showed a series of fibers all in orthorhombic LaFeO₃ phase but no other impurities. In addition, the photocatalytic activity of LaFeO₃ nanofibers was studied for the degradation of methylene blue under visible light. The results demonstrated that ribbon-like nanofibers exhibited excellent photocatalytic activity compared with the others and the LaFeO₃ nanobelts calcined at 500°C had the best photocatalytic activity. Based on the experimental results, possible forming mechanisms involving in LaFeO₃ nanofibers through different needles are also discussed.     

Melamine-barbiturate/cyanurate binary organogels possessing rigid azobenzene-tether moiety

Binary organogels were prepared from coaggregates of azobenzene-tethered melamine dimer and cyanurate/barbiturates. In the gels of hydrocarbon liquids, the coaggregates formed heavily entangled nanofibers, morphologies of which are dramatically different from the previously reported coaggregates based on flexible dodecamethylene-tethered melamine dimers. In the present systems, the rigidity of the azobenzene tether may induce regular packing of molecules. In addition, UV-vis and IR spectroscopic measurements provided unequivocal evidence for the contribution of the central amide groups and the azobenzene chromophores in the tether moiety upon forming well-defined nanofibers by hydrogen-bonding and face-to-face (H-type) pi-pi stacking interactions, respectively. As a result of tight molecular packing in the self-assembled nanofibers, the azobenzene moiety in the gel state showed remarkable resistance to trans --> cis isomerization upon irradiation with UV light.     

Fundamental study of crystallization,orientation, and electrical conductivity of electrospun PET/carbon nanotube nanofibers

The morphology, structure, and properties of polyethylene terephthalate (PET)/Carbon Nanotubes (CNT) conductive nanoweb were studied in this article. Nanocomposite nanofibers were obtained through electrospinning of PET solutions in trifluoroacetic acid (TFA)/dichloromethane (DCM) containing different concentrations and types of CNTs. Electrical conductivity measurements on nanofiber mats showed an electrical percolation threshold around 2 wt % multi‐wall carbon nanotubes (MWCNT). The morphological analysis results showed smoother nanofibers with less bead structures development when using a rotating drum collector especially at high concentrations of CNTs. From crystallographic measurements, a higher degree of crystallinity was observed with increasing CNT concentrations above electrical percolation. Spectroscopy results showed that both PET and CNT orientation increased with the level of alignment of the nanofibers when the nanotube concentration was below the electrical percolation threshold; while the orientation factor was reduced for aligned nanofibers with higher content in CNT. Considerable enhancement in mechanical properties, especially tensile modulus, was found in aligned nanofibers; at least six times higher than the modulus of random nanofibers at concentrations below percolation. The effect of alignment on the mechanical properties was less important at higher concentrations of CNTs, above the percolation threshold. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2052–2064, 2010     

静电纺丝制备g-C3N4/C纳米纤维及其可见光降解性能

采用g-C_3N_4纳米片与聚丙烯腈进行静电复合纺丝,再经预氧化和碳化制得g-C_3N_4/C纳米纤维。利用傅立叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)、拉曼光谱(Raman)和扫描电子显微镜(SEM)对样品结构和形貌进行表征,通过紫外-可见漫反射光谱(UV-Vis DRS)分析可见光响应性。研究表明,复合纳米纤维对罗丹明B表现出较好的可见光降解活性,源于无定形相/石墨相混合结构的碳基体能够降低g-C_3N_4的光生电子-空穴对复合的几率。复合纳米纤维膜在光催化降解搅拌条件下始终能保持完整,经过多次回收和光催化实验,对罗丹明B的光降解率依然较高,表现出较优异的循环利用稳定性。     

静电纺丝制备g-C3N4/C纳米纤维及其可见光降解性能

采用g-C₃N₄纳米片与聚丙烯腈进行静电复合纺丝,再经预氧化和碳化制得g-C₃N₄/C纳米纤维。利用傅立叶变换红外光谱仪（FTIR）、X射线衍射仪（XRD）、拉曼光谱（Raman）和扫描电子显微镜（SEM）对样品结构和形貌进行表征,通过紫外-可见漫反射光谱（UV-Vis DRS）分析可见光响应性。研究表明,复合纳米纤维对罗丹明B表现出较好的可见光降解活性,源于无定形相/石墨相混合结构的碳基体能够降低g-C₃N₄的光生电子-空穴对复合的几率。复合纳米纤维膜在光催化降解搅拌条件下始终能保持完整,经过多次回收和光催化实验,对罗丹明B的光降解率依然较高,表现出较优异的循环利用稳定性。     

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.     

楔形短肽表面活性剂A3V3D纳米自组装结构的表征及机理研究

通过对传统短肽表面活性剂氨基酸序列的改良, 设计了具有楔形几何结构的新型短肽表面活性剂A3V3D. 圆二色谱(CD)分析表明, 该短肽的二级结构为无规则卷曲, 透射电子显微镜(TEM)和原子力显微镜(AFM)表征发现, 该短肽在水溶液中能够发生有序的自组装, 形成稳定的光滑平直的纳米纤维. 芘探针荧光光谱分析显示, 该短肽形成了疏水区并将芘分子包裹其中. 由此推测A3V3D在其楔形几何结构的影响下, 以柱状胶束的形式发生自组装, 是一种新型的自组装短肽材料, 说明了几何形状效应在控制短肽的自组装行为中起着关键作用.