Nanoscale Fibers Research Articles

Electrospun nanofiber of cobalt titanate perovskite as an enhanced heterogeneous catalyst for activating peroxymonosulfate in water

As perovskite-type metal oxides are attractive catalysts for activating peroxymonosulfate (PMS), cobalt titanate (CoTiO3 (CTO)) is particularly promising as CTO consists of earth-abundant Ti and Co is the most effective metal for PMS activation. However, conventional preparation methods of CTO result in large CTO aggregates, leading to very low surface area and porosity, and also limiting its performance. In the present study, an electrospinning technique is employed to prepare CTO nanoscale fiber (CTONF), which can exhibit a consistent nanoscale fibrous morphology, enabling CTO to exhibit a relatively large surface area and porosity, as well as mesoporous structures. Thus, CTONF shows a higher catalytic activity than the bulk CTO for activating PMS to degrade a model toxicant, Amaranth (AR) dye. The PMS activation behaviors are further investigated by examining the effects of temperature, pH, and NaCl on AR degradation by CTONF-activated PMS (CTONF-PMS). Through the effects of probe reagents, the AR degradation mechanism can be attributed primarily to sulfate radicals and hydroxyl radicals to a lesser extent. CTONF was also proven to activate PMS over multiple cycles without regeneration. These results reveal that CTONF is a high effective and recyclable heterogeneous catalyst for PMS activation as it outperforms the conventional bulk CTO. The findings obtained in this study also demonstrate that the electrospinning technique can be utilized to prepare perovskites with enhanced physical and chemical properties for catalytic advanced oxidation applications.

Nanoscale fibers get drug delivery just right

Nanoscale fibers get drug delivery just right

Sensing sound with a nanoscale fiber

A feasibility study is presented of the use of a thin fiber to detect sound. The fiber is assumed to be supported on each end, with a deflection in response to a sound wave that propagates in the direction perpendicular to its long axis. The driving force on the fiber is the result of viscous forces in the oscillating air, which are well-known to be very important in determining the flow-induced motion of small structures. A simplified analytical model of the fiber's response is presented where it is argued that for fibers that are sufficiently thin, elastic and inertial effects become strongly dominated by viscous forces in the fluid. As a result, the fiber's motion becomes a very close approximation of that of the acoustic flow in its vicinity. Electrodynamic transduction of the fiber's motion provides a means of sensing sound with remarkable accuracy if the fiber diameter is taken to be measurably below one micron.

Morphology, transport characteristics and viscoelastic polymer chain confinement in nanocomposites based on thermoplastic potato starch and cellulose nanofibers from pineapple leaf

Eco-friendly “green” nano composites were fabricated from potato starch and cellulose nanofibers from pineapple leaf. Nanocomposites of starch/cellulose nanofibers were prepared by solution mixing followed by casting. The investigation of the viscoelastic properties confirms starch macromolecular chain confinement around the nano scale cellulose surface, superior dispersion and very good interaction between thermoplastic starch and cellulose nanofibers. The degree of chain confinement was quantified. The chain confinement was associated with the immobilization of the starch macromolecular chains in the network formed by the nano-scale cellulose fibers as a result of hydrogen boding interactions. From the results, it was assumed that the starch glycerol system exhibits a heterogenous nature and cellulose nanofibers tend to move towards glycerol rich starch phase. Barrier properties also improved with the addition of nanofiller up to 3wt.% but further addition depreciated properties due to possible fiber agglomeration. The kinetics of diffusion was investigated and typical kinetic parameters were determined and found that the nanocomposites follow pseudo fickian behaviour. The outcome of the work confirms that the prepared nanocomposites films can be used as a swap for packaging applications.

Fabrication of Hydroxyapatite Nanofiber via Electrospinning as a Carrier for Protein.

Hydroxyapatite (HAp) nanoscale fibers were produced by combining electrospinning and a sol–gel system. The fibers were electrospun from a mixture of polymer-calcium phosphate (CaP) sol, then subjected to heat treatment. XRD, FTIR, SEM and TEM with HRTEM analyses confirmed HAp nanofibers with the average fiber diameters varied from 80 to 110 nm can be produced. The effects of concentrations of CaP sol and thermal treatment on the structure of nanofiber were studied. Decreasing the concentration of sol in the mixture can produce HAp fibers with smaller diameters; while higher concentrations of the sol resulted in HAp ceramic fibers with porous structures. The possibility of using HAp nanofiber particles as a controlled release carrier of protein was examined. The amount of protein adsorbed onto HAp fibers decreased as the concentration of the sol and the temperature of heat treatment increased. The sustained release of Bovine serum albumin (BSA) from HAp nanofiber was observed. The study provides information relevant to the fabrication and bioapplication of ceramic nanofiber.

Fabrication of electropsun PLGA and small intestine submucosa-blended nanofibrous membranes and their biocompatibility for wound healing

In recent decades, tremendous research has focused on the production of nanoscale fibers using synthetic polymers, with the goal of fabricating nanofibrous scaffolds for wound healing. However, the hydrophobicity of such polymers typically hinders attachment and proliferation of the cells. In this study, we combined poly-d,l-lactide-co-glycolide (PLGA) and small intestine submucosa (SIS) to fabricate blended nanofibers for wound healing by electrospinning. PLGA and SIS were dissolved in 1,1,1,3,3,3-hexafluoro isopropanol to produce different weight ratios of PLGA/SIS-blended nanofibrous membranes (NFM). Physicochemical characterization of the electrospun NFM was performed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, water contact angle analysis, degradation test and tensile testing. The PLGA/SIS-blended NFM showed improved hydrophilicity and tensile strength. Better infiltration, attachment and proliferation of rat granulation fibroblasts of PLGA/SIS-blended NFMs compared to PLGA NFMs were identified by morphological differences determined by SEM and a water-soluble tetrazolium salt assay kit. Based on our results, the PLGA/SIS blended NFMs were found to be suitable for use as a potential material for wound dressing.

Strong size-dependent stress relaxation in electrospun polymer nanofibers

Electrospun polymer nanofibers have garnered significant interest due to their strong size-dependent material properties, such as tensile moduli, strength, toughness, and glass transition temperatures. These properties are closely correlated with polymer chain dynamics. In most applications, polymers usually exhibit viscoelastic behaviors such as stress relaxation and creep, which are also determined by the motion of polymer chains. However, the size-dependent viscoelasticity has not been studied previously in polymer nanofibers. Here, we report the first experimental evidence of significant size-dependent stress relaxation in electrospun Nylon-11 nanofibers as well as size-dependent viscosity of the confined amorphous regions. In conjunction with the dramatically increasing stiffness of nano-scaled fibers, this strong relaxation enables size-tunable properties which break the traditional damping-stiffness tradeoff, qualifying electrospun nanofibers as a promising set of size-tunable materials with an unusual and highly desirable combination of simultaneously high stiffness and large mechanical energy dissipation.

Fabrications and mechanical behaviors of amorphous fibers

Mechanical properties of micro- and nanoscale fibers are superior to their bulk counterparts, and their mechanical behaviors are different from each other. Homogeneous amorphous fibers with smooth surfaces and controllable sizes can be continuously drawn from supercooled liquid. Compared with the preparing of crystalline fibers, the manufacturing of amorphous fibers saves much energy and time. Furthermore, amorphous materials have excellent mechanical properties due to their short-ranged ordered and long-ranged disordered structures. Therefore, amorphous fibers have wide engineering applications and research interest. In this paper we review the fabrication and mechanical behaviors of amorphous fibers with excellent mechanical properties including oxide glass fibers and amorphous alloy fibers.There are continuous and discontinuous oxide glass micro-fibers. Discontinuous oxide glass micro-fibers can be fabricated by techniques in which a thin thread of melt flowing from the bottom of a container is broken into segments. Continuous oxide micro-fibers can be fabricated by techniques in which a filament of supercooled liquid is drawn from melt. However, oxide glass nano-fibers can be fabricated by chemical vapor deposition, laser ablation, sol-gel, and thermal evaporation methods. Fabrication techniques of amorphous alloy fibers are very different from those of oxide glass fibers. These techniques adopt in-rotating-water spinning method, melt-extraction method, Taylor method, nanomoulding method, fast drawing method, melt drawing method, and gas atomization method.Microscale oxide glass fiber has a facture strength as high as 6 GPa. The fracture strength of nanoscale oxide glass fiber can reach 26 GPa which is close to the theoretical strength of 30 GPa. On the other hand, the plasticity of microscale amorphous alloy fibers is mediated by shear banding. The shear band spacing decreases with reducing sample size in bending. However, there is no tensile plasticity in microscale amorphous alloy fibers. When the sample size is smaller than the size of shear band core (500 nm), inhomogeneous plastic deformation transforms into homogeneous plastic deformation. The tensile plasticity of amorphous alloy is significantly improved. The homogeneous plastic deformation is mediated by catalyzed shear transformation. The catalyzed shear transformation may be the origin of hardening behaviors of nanoscale amorphous alloy fibers.Fianlly, we summary the unsolved problems in the fabrications and mechanical behaviors of amorphous fibers, and discuss the prospect of amorphous fibers.

Design and Development of a Series-configuration Mazzilli Zero Voltage Switching Flyback Converter as a High-voltage Power Supply for Needleless Electrospinning

Nanofiber is one-dimensional material that has broad application. It can be formed by applying a high-voltage source to a polymer solution so that the polymer solution becomes charged. Usingthe high electric field, the charged polymer solution is formed as a Taylor cone and then drawn to the collector to form long, nanoscale fibers. This method is known as electrospinning. There are two types of electrospinning method; they are needle and needleless electrospinning. The latter is intended for mass production nanofibers because it can make tens to hundreds ofjets at a time. Therefore, the high-voltage source required for the needleless electrospinning process must have a higher voltage and current compared to those for the needle one. Accordingly, the high voltage power supply using a series-configuration Mazzilli ZVS flyback converter was designed and developed. The Mazzilli flyback converter was able to generate a high voltage with relatively high power. Two converters were connected in series to achieve more output voltage. The output voltage was adjusted by changing the input voltage. The single converter could generate a high voltage up to 34kV whereas the series-configuration converter could increase the voltage by 98.41% to be 67kV. The output voltage of converter was relatively stable and good enough to perform nanofibers synthesis using the needleless electrospinning. Visual observation confirmed that the nanofibers were formed well on the collector.

Production of polyvinylidene fluoride nanofibers by free surface electrospinning from wire electrode

Electrospinning is the manufacturing technology for production nanoscale fibers from the polymer solution. The technique is operated in an electric field with high voltage electrical potential between two conductive electrodes. A needle is used as the anode in laboratory generally. However, the needle process is low productivity for commercialization. Free surface electrospinning is designed for solving the problem. Component use as electrodes isn’t a needle. In this work represented a needle anode by a wire electrode for increasing mass production. Polymer solution droplets were entrained on a wire and control uniformity of themselves droplet. High voltage potential could be applied between wire and ground plate on the top. Polyvinylidene fluoride (PVDF) was used as a precursor to prepared nanofiber. Morphologies of nanofibers were characterized using scanning electron microscope, which informed surface description of the nanofiber. Free surface electrospinning is alternative electrostatic fiber formation technique that can produce the nanofibers thin films continuously. This process convenient for apply in roll to roll process and useful for large scale production.

Advanced bioplymeric electrospun nanoscale fibers for controlled drug delivery

Advanced bioplymeric electrospun nanoscale fibers for controlled drug delivery

Fabricating high mechanical strength γ-Fe2O3 nanoparticles filled poly(vinyl alcohol) nanofiber using electrospinning process potentially for tissue engineering scaffold

The use of electrospinning has gained substantial interest in the development of tissue engineering scaffolds due to its ability to produce nanoscale fibers which can mimic the geometry of extracellular tissues. Besides geometry, mechanical property is one of the main elements to be considered when developing tissue engineering scaffolds. In this study, the electrospinning process parameter settings were varied in order to find the optimum setting which can produce electrospun nanofibrous mats with good mechanical properties. Maghemite (γ-Fe2O3) was mixed with poly(vinyl alcohol) and then electrospun to form nanofibers. The five input variable factors involved were nanoparticles content, voltage, flow rate, spinning distance, and rotating speed, while the response variable considered was Young’s modulus. The performance of electrospinning process was systematically screened and optimized using response surface methodology. This work truly demonstrated the sequential nature of designed experimentation. Additionally, the application of various designs of experiment techniques and concepts was also demonstrated. Results revealed that electrospun nanofibrous mats with maximum Young’s modulus (273.51 MPa) was obtained at optimum input settings: 9 v/v% nanoparticle content, 35 kV voltage, 2 mL/h volume flow rate, 8 cm spinning distance, and 3539 r/min of rotating speed. The model was verified successfully by performing confirmation experiments. The nanofibers characterization demonstrated that the nanoparticles were well dispersed inside the nanofibers, and it also showed that the presence of defects on the nanofibers can decrease their mechanical strength. The biocompatibility performance was also evaluated and it was proven that the presence of γ-Fe2O3 enhanced the cell viability and cell growth rate. The developed poly(vinyl alcohol)/γ-Fe2O3 electrospun nanofiber mat has a good potential for tissue engineering scaffolds.

Recent development of centrifugal electrospinning

ABSTRACTAs a high‐output nanoscale fiber production method, centrifugal electrospinning (CES) has attracted increasing attention, and this has fostered its quick development. In this article, we review this technique and summarize its mechanism, characteristics, classification, and process equipment. Furthermore, we classify the effects of several CES process parameters on the fiber properties into three different categories. The mechanisms of these effects on the fiber characteristics are analyzed. Finally, the CES issues are summarized, and some strategic solutions and prospects are proposed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44578.

Sequence basis of Barnacle Cement Nanostructure is Defined by Proteins with Silk Homology.

Barnacles adhere by producing a mixture of cement proteins (CPs) that organize into a permanently bonded layer displayed as nanoscale fibers. These cement proteins share no homology with any other marine adhesives, and a common sequence-basis that defines how nanostructures function as adhesives remains undiscovered. Here we demonstrate that a significant unidentified portion of acorn barnacle cement is comprised of low complexity proteins; they are organized into repetitive sequence blocks and found to maintain homology to silk motifs. Proteomic analysis of aggregate bands from PAGE gels reveal an abundance of Gly/Ala/Ser/Thr repeats exemplified by a prominent, previously unidentified, 43 kDa protein in the solubilized adhesive. Low complexity regions found throughout the cement proteome, as well as multiple lysyl oxidases and peroxidases, establish homology with silk-associated materials such as fibroin, silk gum sericin, and pyriform spidroins from spider silk. Distinct primary structures defined by homologous domains shed light on how barnacles use low complexity in nanofibers to enable adhesion, and serves as a starting point for unraveling the molecular architecture of a robust and unique class of adhesive nanostructures.

Polymer fiber-based models of connective tissue repair and healing.

Physiologically relevant models of wound healing are essential for understanding the biology of connective tissue repair and healing. They can also be used to identify key cellular processes and matrix characteristics critical for the design of soft tissue grafts. Modeling the various stages of repair post tendon injury, polymer meshes of varying fiber diameter (nano-1 (390nm)<nano-2 (740nm)<micro (1420nm)) were produced. Alignment was also introduced in the nano-2 group to model matrix undergoing biological healing rather than scar formation. The response of human tendon fibroblasts on these model substrates were evaluated over time as a function of fiber diameter and alignment. It was observed that the repair models of unaligned nanoscale fibers enhanced cell growth and collagen synthesis, while these outcomes were significantly reduced in the mature repair model consisting of unaligned micron-sized fibers. Organization of paxillin and actin on unaligned meshes was enhanced on micro- compared to nano-sized fibers, while the expression and activity of RhoA and Rac1 were greater on nanofibers. In contrast, aligned nanofibers promoted early cell organization, while reducing excessive cell growth and collagen production in the long term. These results show that the early-stage repair model of unaligned nanoscale fibers elicits a response characteristic of the proliferative phase of wound repair, while the more mature model consisting of unaligned micron-sized fibers is more representative of the remodeling phase by supporting cell organization while suppressing growth and biosynthesis. Interestingly, introduction of fiber alignment in the nanofiber model alters fibroblast response from repair to healing, implicating matrix alignment as a critical design factor for circumventing scar formation and promoting biological healing of soft tissue injuries.

The utility of the in vitro micronucleus test for evaluating the genotoxicity of natural and manmade nano-scale fibres

A range of fibrous materials, including several types of asbestos and carbon fibres with nano scale diameters that had reported positive genotoxicity data (predominantly clastogenicity), were tested in the in vitro micronucleus test (OECD 487) in GLP-compliant studies in Chinese Hamster Ovary cells. Out of eight materials tested, only one (crocidolite, an asbestos fibre) gave a positive response either in the presence or absence of metabolic activation (S9) and at short (3h) or extended (24h) exposure times (p≤0.001). Our data suggest that the commonly used tests for clastogenicity in mammalian cells require extensive modification before fibrous materials are detected as positive, raising questions about the validity of these tests for detecting clastogenic and aneugenic fibrous materials.

Synthesis of polycaprolactone-titanium oxide multilayer films by nanosecond laser pulses and electrospinning technique for better implant fabrication

In this study, a combination of electrospinning and laser texturing is introduced as a novel method for increasing the biocompatibility of metal implants. Besides having a rough laser treated surface, the implant benefits from the high porosity and better wettability of an electrospun fibrous structure, which is a more favorable environment for cell proliferation. Titanium samples were patterned using a nanosecond laser beam and were placed as collectors in an electrospinning machine. They were then soaked in simulated body fluid for four weeks. Energy Dispersive X-ray and X-Ray Diffraction results indicate significantly more hydroxyapatite formation on laser treated samples with nanoscale fibers deposited on their surface. This shows that having a laser treated surface underneath the fibrous layer can improve short-term biocompatibility even before degradation of fibers. The thermal conductivity of the electrospun layer, measured using a Hot Disk Transient Plane Source instrument and computer code, was shown to be considerably lower than that of titanium and very close to bone. The presence of this layer can therefore be beneficial in making the implant more compatible to a biological medium. In case of dental implants, it was shown that this layer can act as a thermal barrier while a hot beverage is consumed and it can decrease the temperature rise by about 60%, which avoids any possible damage to newly formed cells during the healing period.

Vascular Endothelial Growth Factor Improves Physico-Mechanical Properties and Enhances Endothelialization of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Poly(ε-caprolactone) Small-Diameter Vascular Grafts In vivo

The combination of a natural polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and a synthetic hydrophobic polymer poly(ε-caprolactone) (PCL) is promising for the preparation of biodegradable and biocompatible small-diameter vascular grafts for bypass surgery. However, physico-mechanical properties and endothelialization rate of PHBV/PCL grafts are poor. We suggested that incorporation of vascular endothelial growth factor (VEGF) into PHBV/PCL grafts may improve their physico-mechanical properties and enhance endothelialization. Here we compared morphology, physico-mechanical properties, and in vivo performance of electrospun small-diameter vascular grafts prepared from PHBV/PCL with and without VEGF. Structure of the graft surface and physico-mechanical properties were examined by scanning electron microscopy and universal testing machine, respectively. Grafts were implanted into rat abdominal aorta for 1, 3, and 6 months with the further histological, immunohistochemical, and immunofluorescence examination. PHBV/PCL grafts with and without VEGF were highly porous and consisted mostly of nanoscale and microscale fibers, respectively. Mean pore diameter and mean pore area were significantly lower in PHBV/PCL/VEGF compared to PHBV/PCL grafts (1.47 μm and 10.05 μm2; 2.63 μm and 47.13 μm2, respectively). Durability, elasticity, and stiffness of PHBV/PCL grafts with VEGF were more similar to internal mammary artery compared to those without, particularly 6 months postimplantation. Both qualitative examination and quantitative image analysis showed that three-fourths of PHBV/PCL grafts with VEGF were patent and had many CD31-, CD34-, and vWF-positive cells at their inner surface. However, all PHBV/PCL grafts without VEGF were occluded and had no or a few CD31-positive cells at the inner surface. Therefore, VEGF enhanced endothelialization and improved graft patency at all the time points in a rat abdominal aorta replacement model. In conclusion, PHBV/PCL grafts with VEGF have better biocompatibility and physico-mechanical properties compared to those without. Incorporation of VEGF improves graft patency and accelerates formation of endothelial cell monolayer.

Evaluation of poly ε-caprolactone electrospun nanofibers loaded with Hypericum perforatum extract as a wound dressing

In this study, for the first time, a biocompatible and non-toxic herbal wound dressing was made by encapsulation of Hypericum perforatum alcoholic extract at different concentrations (10, 30 and 50 % v/v) into poly e-caprolactone electrospun nanofibers to achieve an effective wound dressing. The electrospinning processing parameters such as needle tip to collector distance, applied voltage and flow rate of feed solution were changed until accumulated nano-scale fibers without bead structures were obtained. Then, the morphology of the nanofibrous structures was investigated by scanning electron microscopy. After synthesis of the nanofibers in optimal conditions, the antibacterial activity of the optimized bandages was investigated by the disc diffusion method against strains of Staphylococcus aureus and Escherichia coli. The release content of the herbal drug was tested by the total immersion method in phosphate buffer saline and displayed a constant drug liberation with time. Water vapor transmission rate for the wound dressing was evaluated by pseudo-extra cellular fluid for optimal samples. The crystallinity and thermal behavior of the mats with and without H. perforatum alcoholic extract were studied by X-ray diffraction and differential scanning calorimetry. The results of antibacterial activity, cell culture and In vitro methyl thiazolyl tetrazolium assays demonstrated these unique structures as being very useful as burn and ulcer dressings.

Fiber Grating-Assisted Surface Plasmon Resonance for Biochemical and Electrochemical Sensing

Surface plasmon resonance (SPR) optical fiber sensors can be used as a cost-effective and relatively simple-to-implement alternative to well established bulky prism configurations for in situ high sensitivity biochemical and electrochemical measurements. The miniaturized size and remote operation ability offer them a multitude of opportunities for single-point sensing in hard-to-reach spaces, even possibly in vivo . Grating-assisted and polarization control are two key properties of fiber-optic SPR sensors to achieve unprecedented sensitivities and limits of detection. The biosensor configuration presented here utilizes a nanoscale metal-coated tilted fiber Bragg grating (TFBG) imprinted in a commercial single-mode fiber core with no structural modifications. Such sensor provides an additional resonant mechanism of high-density narrow cladding mode spectral combs that overlap with the broader absorption of the surface plasmon for high accuracy interrogation. In this paper, we briefly review the principle, characterization and implementation of plasmonic TFBG sensors, followed by our recent developments of the “surface” and “localized” affinity studies of the biomolecules for real life problems and the electrochemical actives of electroactive biofilms for clean energy resources.