PEG-PLA-PCL based electrospun yarns with curcumin control release property as suture

This work presents an interesting method using an electrospinning process to fabricate suture yarns loaded with curcumin to achieve reasonable mechanical properties as well as tunable drug release behavior. Different structures including different yarn counts and twists as well as core-sheath structures were used to adjust drug release properties along with improving the yarn's mechanical properties. The core parts were made of polycaprolactone and the sheath parts were made of polyethylene glycol, polylactic acid, and polycaprolactone. Drugs can be incorporated in both parts based on the required condition and application. Electrospun yarns were compared using both structural properties and their drug release profiles as metrics. The results of comparing drug release profiles of six electrospun yarns with different yarn counts and twists showed that yarns with finer fiber diameters in the core part have more drug release as well as more initial release. Overall evaluations showed that core-sheath drugloaded yarn with appropriate physical and mechanical properties can be a useful material as a drug delivery system to the site of damaged tissue. It can also be concluded that the amount and duration of drug release can be controlled using the structural parameters of electrospun yarns as an engineering tool for designing suture yarns with required properties.     

Composite core-double sheath fibers based on some biodegradable polyesters obtained by self-organization during electrospinning

Obtaining core-sheath fibers by single-spinneret electrospinning is a recent and straightforward approach to prepare composite fibers. Fibers of more complex architecture consisting of poly(ethylene oxide) (PEO) core, inner poly(l -lactide) sheath sd and outer beeswax (BW) sheath may also be obtained using this method. In the present study we report its applicability for a large series of (bio)degradable polyesters such as poly(ε-caprolactone), poly(d ,l -lactide-co-glycolide), poly(butylene succinate), poly(3-hydroxybutyrate), and poly(l -lactide-co-d ,l -lactide). The fibers have a well-differentiated PEO core, polyester inner sheath and BW outer sheath. The possibility for targeted location of hydrophilic or hydrophobic substances in the core or in the sheaths of the PEO/polyester/BW fibers has been demonstrated using nanosized zinc oxide with unmodified (hydrophilic) or silanized (hydrophobic) surface. PEO/polyester/BW fibrous materials loaded with a model drug (5-nitro-8-hydroxyquinoline) exhibit antimicrobial activity. The obtained results show that single-spinneret electrospinning is a novel and versatile method to prepare core-double sheath composite fibers prospective for various applications such as biomedicine, cosmetics, and food packaging.     

Formation and characterization of core-sheath nanofibers through electrospinning and surface-initiated polymerization

Novel core-sheath nanofibers, composed of polyacrylonitrile (PAN) core and polypyrrole (PPy) sheath with clear boundary between them, were fabricated by electrospinning PAN/FeCl₃·6H₂O bicomponent nanofibers and the subsequent surface-initiated polymerization in a pyrrole-containing solution. By adjusting the concentration of FeCl₃·6H₂O, the surface morphology of PPy sheath changed from isolated agglomerates or clusters to relatively uniform thin-film structure. Thermal properties of PAN-PPy core-sheath nanofibers were also characterized. Results indicated that the PPy sheath played a role of inhibitor and retarded the complex chemical reactions of PAN during the carbonization process.     

Dual Drug Release Electrospun Core-Shell Nanofibers with Tunable Dose in the Second Phase

This study reports a new type of drug-loaded core-shell nanofibers capable of providing dual controlled release with tunable dose in the second phase. The core-shell nanofibers were fabricated through a modified coaxial electrospinning using a Teflon-coated concentric spinneret. Poly(vinyl pyrrolidone) and ethyl cellulose were used as the shell and core polymer matrices respectively, and the content of active ingredient acetaminophen (APAP) in the core was programmed. The Teflon-coated concentric spinneret may facilitate the efficacious and stable preparation of core-shell nanofibers through the modified coaxial electrospinning, where the core fluids were electrospinnable and the shell fluid had no electrospinnability. The resultant nanofibers had linear morphologies and clear core-shell structures, as observed by the scanning and transmission electron microscopic images. APAP was amorphously distributed in the shell and core polymer matrices due to the favorite second-order interactions, as indicated by the X-ray diffraction and FTIR spectroscopic tests. The results from the in vitro dissolution tests demonstrated that the core-shell nanofibers were able to furnish the desired dual drug controlled-release profiles with a tunable drug release amount in the second phase. The modified coaxial electrospinning is a useful tool to generate nanostructures with a tailored components and compositions in their different parts, and thus to realize the desired functional performances.     

Synthesis of Graphene Oxide/Iron Oxide/Au Nanocomposite for Quercetin Delivery

This study focused on developing a superparamagnetic graphene oxide-based nanocomposite consisting of iron oxide (IO) and gold nanoparticles for quercetin delivery. For this purpose, the structure and morphology of the designed nanocomposite (GO/IO/Au) were investigated by several characterization methods such as fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, vibrating-sample magnetometer (VSM) analysis, field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM). Then, the biocompatibility of the synthesized nanocomposite was studied by Brine shrimp Artemia lethality assay, red blood cell hemolysis assay, and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. Moreover, the GO/IO/Au nanocomposite efficiency as an anticancer drug delivery system was evaluated in vitro conditions. The results showed that the designed nanocomposite is highly biocompatible and possesses a favorable magnetization (M_s?=?29.2 emu.g^?1) making it a good candidate for biomedical applications. Also, it was confirmed that GO/IO/Au nanocomposite is a potent drug carrier that can effectively deliver quercetin to cancer cells.

     

Preparation of Coaxial-Electrospun Poly[bis(p-methylphenoxy)]phosphazene Nanofiber Membrane for Enzyme Immobilization

A core/sheath nanofiber membrane with poly[bis(p-methylphenoxy)]phosphazene (PMPPh) as the sheath and easily spinnable polyacrylonitrile (PAN) as the core was prepared via a coaxial electrospinning process. Field-emission scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the nanofiber membrane. It was found that the concentration of the PAN spinning solution and the ratio of the core/sheath solution flow rates played a decisive role in the coaxial electrospinning process. In addition, the stabilized core/sheath PMPPh nanofiber membrane was investigated as a support for enzyme immobilization because of its excellent biocompatibility, high surface/volume ratio, and large porosity. Lipase from Candida rugosa was immobilized on the nanofiber membrane by adsorption. The properties of the immobilized lipase on the polyphosphazene nanofiber membrane were studied and compared with those of a PAN nanofiber membrane. The results showed that the adsorption capacity (20.4 ± 2.7 mg/g) and activity retention (63.7%) of the immobilized lipase on the polyphosphazene nanofiber membrane were higher than those on the PAN membrane.     

Effect of PVA content on morphology,swelling and mechanical property of crosslinked chitosan/PVA nanofibre

Abstract

Crosslinked chitosan/poly(vinyl alcohol) nanofibres were successfully prepared via electrospinning technique with heat mediated chemical crosslinking. The structure, morphology and mechanical properties of nanofibres were characterised by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and tensile tester respectively. The SEM images demonstrated that crosslinked nanofibres exhibited a smooth surface and regular morphology. With increasing PVA, swelling of nanofabric increased. The mechanical properties of the fibre mats, as determined in a static tensile test, improved with increasing PVA composition owing to strong interaction between chitosan and poly(vinyl alcohol) molecular resulted from intermolecular hydrogen bonds. The crosslinked chitosan/poly (vinyl alcohol) nanofibrous mats have potential use as artificial skin and other tissue scaffold materials.     

Enhancing antibacterial properties of polypropylene/Cu‐loaded montmorillonite nanocomposite filaments through sheath–core morphology

Polypropylene (PP) loaded with copper‐exchanged montmorillonite (Cu‐MMT) nanocomposite filaments and films with excellent antimicrobial activity have been reported for the first time. A sheath–core morphology filament in which only the sheath contains Cu‐MMT was prepared for maximizing bioactivity. Sodium MMT clay was modified to acid‐activated MMT and further to Cu‐MMT via an ion exchange process. The exchange operation was confirmed using wide‐angle X‐ray diffraction and energy‐dispersive X‐ray spectroscopy (EDX) which suggested increased interlayer spacing and confirmed the loading of copper in Cu‐MMT. Further, Cu‐MMT was melt‐mixed in PP in the form of PP/Cu‐MMT nanocomposite filament, film and sheath–core morphology PP/Cu‐MMT nanocomposite filament. The surface morphology and elemental composition of the nanocomposites were studied using scanning electron microscopy coupled with EDX. Transmission electron micrographs were obtained to understand the dispersion characteristics of Cu‐MMT phase in PP. X‐ray diffraction analysis of nanocomposites suggested increased crystallinity at lower loading due to heterogeneous nucleating action of MMT. The PP nanocomposite filaments and films were tested for antimicrobial activity against Gram‐negative bacterium Escherichia coli, which is the main pathogenic bacterium found abundantly in water, and were found to exhibit excellent antimicrobial activity. © 2018 Society of Chemical Industry     

Functional Hyaluronic Acid-Polylactic Acid/Silver Nanoparticles Core-Sheath Nanofiber Membranes for Prevention of Post-Operative Tendon Adhesion

In this study, we prepared core-sheath nanofiber membranes (CSNFMs) with silver nanoparticles (Ag NPs) embedding in the polylactic acid (PLA) nanofiber sheath and hyaluronic acid (HA) in the nanofiber core. The PLA/Ag NPs sheath provides mechanical support as well as anti-bacterial and anti-inflammatory properties. The controlled release of HA from the core could exert anti-adhesion effects to promote tendon sliding while reducing fibroblast attachment. From the microfibrous structural nature of CSNFMs, they function as barrier membranes to reduce fibroblast penetration without hampering nutrient transports to prevent post-operative peritendinous adhesion. As the anti-adhesion efficacy will depend on release rate of HA from the core as well as Ag NP from the sheath, we fabricated CSNFMs of comparable fiber diameter, but with thick (Tk) or thin (Tn) sheath. Similar CSNFMs with thick (Tk⁺) and thin (Tn⁺) sheath but with embedded Ag NPs in the sheath were also prepared. The physico-chemical properties of the barrier membranes were characterized in details, together with their biological response including cell penetration, cell attachment and proliferation, and cytotoxicity. Peritendinous anti-adhesion models in rabbits were used to test the efficacy of CSNFMs as anti-adhesion barriers, from gross observation, histology, and biomechanical tests. Overall, the CSNFM with thin-sheath and Ag NPs (Tn⁺) shows antibacterial activity with low cytotoxicity, prevents fibroblast penetration, and exerts the highest efficacy in reducing fibroblast attachment in vitro. From in vivo studies, the Tn⁺ membrane also shows significant improvement in preventing peritendinous adhesions as well as anti-inflammatory efficacy, compared with Tk and Tn CSNFMs and a commercial adhesion barrier film (SurgiWrap^®) made from PLA.     

Spontaneous core-sheath formation in electrospun nanofibers

In recent research, electrospun nanofibers (NFs) from polymer solutions containing metal salts were used to produce high-temperature superconducting ceramic (HTSC) NFs through pyrolysis. In this research, the production of phase separated nanostructures inside NFs spun from polymer solutions containing metal salts was investigated. The metal salts were expected to be preferentially driven into one of the phases (the amorphous phase in a semi-crystalline polymer and the more hydrophilic phase in a triblock copolymer) and yield nanostructured ceramics upon pyrolysis. Surprisingly, the electrospun NFs exhibited the spontaneous formation of a core-sheath structure. The metal-atom-rich core exhibited a 10 nm scale structure while no such structure was observed in the metal-atom-poor sheath. Both the repulsion of metal atoms by the positive surface charge and the exclusion of the metal atoms from the crystallizing front that moves inward from the surface were shown to contribute to the spontaneous formation of the core-sheath structure.     

Electrospun Poly(ε-Caprolactone)/Silk Fibroin Coaxial Core-Sheath Nanofibers Applied to Scaffolds and Drug Carriers

Developing biologically mimetic nanofibers (NFs) is crucial for their applications as scaffolds in tissue engineering and drug carriers. Herein, we present a strategy to facilely fabricate core-sheath NFs using coaxial electrospinning technique. Poly(ε-caprolactone) (PCL) and silk fibroin (SF) were employed as component materials to construct PCL/SF NFs with PCL cores uniformly encapsulated by SF sheaths. Scanning electron microscopy and transmission electron microscopy demonstrate a uniform core-sheath structure of the coaxial NFs. The engineered core-sheath structure confers the composite NFs with greatly improved properties including surface hydrophilicity and mechanical properties. In vitro cell culture validates that the core-sheath NFs are favorable to the cultured rat pheochromocytoma cells (PC 12) attachment. To further demonstrate the advantage of the coupled structural integrity, the PCL/SF core-sheath NFs were compared with the NFs produced from PCL and SF blend. Results showed that the PCL/SF NFs possessed a tensile strength of ~6.93 ± 0.52 MPa and an elongation at break of ~294.31 ± 24.17%, whereas the blend NFs possessed ~5.55 ± 0.50 MPa and ~88.05 ± 13.98%, respectively. Dexamethasone-phosphate sodium (DEX) was employed as a model drug, whereby the in vitro release study indicates that the NFs exhibit an ideal releasing profile, capable of releasing DEX continuously over a period of 450 h. The constructed PCL/SF core-sheath NFs are promising candidates for biomedical applications. POLYM. ENG. SCI., 60:802–809, 2020. © 2020 Society of Plastics Engineers     

Structure,properties, and applications of polyacrylonitrile/carbon nanotube (CNT) fibers at low CNT loading

Bi-component, polyacrylonitrile (PAN)/carbon nanotube (CNT) fibers were processed, at different core-sheath area ratios, by gel spinning. A percolated CNT network at 10 wt% CNT in the sheath enhanced electrical conductivity as compared to the neat PAN fiber, while PAN polymer in the core contributed to the good mechanical properties. Fibers with relatively thin sheath allowed overall CNT loading as low as 3.7 wt% to be made with good electrical conductivity, and PAN stabilization by Joule heating was demonstrated. Such fibers with combined good mechanical properties and electrical conductivity can also potentially be used for electrical heating of fabrics, for making smart textiles, and for electromagnetic interference shielding.     

Production,structure and properties of twistless carbon nanotube yarns with a high density sheath

Carbon nanotube web drawn from a vertically aligned carbon nanotube forest is converted into a twistless yarn by a rubbing roller system. The yarn consists of a high packing density sheath with carbon nanotubes lying straight and parallel to the yarn axis and a low density core with many microscopic voids. The rubbing motion causes carbon nanotubes in the surface layers of the yarn to move in opposite directions and consequently large shear strains in the intermediate region tear the partially densified carbon nanotube assembly apart, resulting in the formation of large voids in the yarn core. The specific tensile modulus and sonic velocity of the core-sheath structured, twistless carbon nanotube yarns are significantly higher than that of their corresponding twist-densified yarns. These improvements have been attributed to increased nanotube-to-nanotube contact length in the high packing density sheath and very few carbon nanotubes lying at an angle to the yarn axis.     

Hexamethylene diamine/carboxymethyl cellulose grafted on magnetic nanoparticles for controlled drug delivery

In this study, chemically modified iron oxide nanoparticles with super paramagnetic behavior and biodegradable properties were prepared through the reaction of a polymeric layer with surface hydroxyl functional groups of magnetic nanoparticles (MNP). For this purpose firstly, MNP was grafted with hexamethylene diisocyanate. Then, carboxymethyl cellulose which was modified with the hexamethylenediamine (mCMC) as a shell was coated and reacted simultaneously on MNP-grafted hexamethylene diisocyanate to form a polymeric core–shell (MNP/mCMC). The structural, morphological, thermal, and magnetic properties of the synthesized magnetite nanocomposite were confirmed by Fourier transform infrared spectrophotometer, thermal gravimetric analysis, X-ray diffraction, vibrating sample magnetometer, and scanning electron microscopy. The size of the resulting MNP/mCMC was approximately between 70 and 120 nm. Doxorubicin (DOX) as a model anticancer drug was used. The in vitro release of DOX from the MNP/mCMC was investigated and indicated that the release speed of the DOX could be well controlled. Release profiles of the DOX and its loading capacity were determined by ultraviolet–visible spectroscopy absorption measurement at λ _max 483 nm. The obtained results suggest that the prepared magnetite nanocomposite would be beneficial as a targeted anti-tumor drug carrier for pharmaceutical applications.     

Characterization and Application of Intercalated Montmorillonite with Verapamil and its Polymethyl Methacrylate Nanocomposite in Drug Delivery

This work examined two drug delivery systems: the first system studied the adsorption of Verapamil hydrochloride drug into montmorillonite clay (MMT) by intercalation process to prepare MMT-Verapamil hybrid at different intercalating time, temperatures, pH values and initial drug concentrations. The second system includes the preparation of MMT-Verapamil hybrid combined with polymethyl methacrylate via an emulsion polymerization process to produce a novel nanocomposite material to be used in drug delivery. The polymerization process was carried out using an ultrasonic technique to achieve a biologically safe drug delivery system. Best conditions for the intercalation of verapamil hydrochloride drug into the interlayer of MMT clay were found to be at 50°C and 1 hr using pH ranges of 4–6. The prepared MMT-Verapamil hybrid and the produced MMT-verapamil-MMA nanocomposite material were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and thermal gravimetric analysis (TGA). The in-vitro release profile of Verapamil in the case of a drug hybrid is faster than the release in the case of a drug nanocomposite in both gastric and intestinal fluids where, in the case of gastric fluid (pH 1.2), about 40% of the loaded drug was released from the drug hybrid in the first 4 h against only 37% in 5 h in the case of drug nanocomposite. Also in the intestinal fluid (pH 7.4), the verapamil release from drug hybrid reached 68% in 5 h against only 57% was released from drug nanocomposites in 7 h.     

Morphology and crystallization behavior of nylon 6‐clay/neat nylon 6 bicomponent nanocomposite fibers

Nylon 6‐clay hybrid/neat nylon 6, sheath/core bicomponent nanocomposite fibers containing 4 wt % of clay in sheath section, were melt spun at different take‐up speeds. Their molecular orientation and crystalline structure were compared to those of neat nylon 6 fibers. Moreover, the morphology of the bicomponent fibers and dispersion of clay within the fibers were analyzed using scanning electron microscopy and transmission electron microscopy (TEM), respectively. Birefringence measurements showed that the orientation development in sheath part was reasonably high while core part showed negligibly low birefringence. Results of differential scanning calorimetry showed that crystallinity of bicomponent fibers was lower than that of neat nylon 6 fibers. The peaks of γ‐crystalline form were observed in the wide‐angle X‐ray diffraction of bicomponent and neat nylon 6 fibers in the whole take‐up speed, while α‐crystalline form started to appear at high speeds in bicomponent fibers. TEM micrographs revealed that the clay platelets were individually and evenly dispersed in the nylon 6 matrix. The neat nylon 6 fibers had a smooth surface while striped pattern was observed on the surface of bicomponent fibers containing clay. This was speculated to be due to thermal shrinkage of the core part after solidification of the sheath part in the spin‐line. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39996.     

DESIGN AND TESTING OF AN AEROSOL/SHEATH INLET FOR HIGH RESOLUTION MEASUREMENTS WITH A DMA

A modified aerosol/sheath inlet was designed for a differential mobility analyzer (DMA) for high resolution measurements based on field model calculations which include fluid flow, electric field, and convective/diffusive transport. To avoid the predicted flow recirculation for the current inlet design at an aerosol-to-sheath flow ratio of 0.05, the slit width is reduced and aerodynamically shaped so that the sheath velocity and aerosol velocity more nearly match. Numerical results are presented comparing the fluid flow of the old and new inlet. Problems associated with the old inlet include: flow unsteadiness at a flow ratio of 0.025, voltage shift at the peak particle concentration as a function of the flow ratio, and the historical observation that, while performing tandem differential mobility analyzer measurements (TDMA), the voltage applied on the second DMA for the peak particle concentration is higher than that for the first. Measurements demonstrate that all these problems are reduced or eliminated with the new inlet design. The TDMA measurements include flow ratios of 0.1, 0.05, 0.025 and 0.0125 at sheath flows of 166 and 333 cm³ s^-1 (10 and 20 l min^-1). The challenge of performing measurements at these low flow ratios will be discussed including flow calibration, flow matching, and pressure monitoring. The new inlet is applied to the measurement of the National Institute of Standards and Technology 0.1 μm Standard Reference Material 1963, and it is shown that the DMA can accurately measure the standard deviation of this narrowly distributed aerosol (σ/D_p=0.02).     

Carbon nanofibre‐reinforced ultrahigh molecular weight polyethylene for tribological applications

Carbon nanofibre (CNF)‐reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposites containing up to 10 wt % of nanofibres were prepared by a novel solvent‐assisted extrusion process using short chain oligomers to tailor the melt viscosity of the UHMWPE matrix. A detailed investigation of the resulting nanocomposite microstructure and of the static mechanical properties revealed that the carbon nanofibres lead to improved mechanical properties of the UHMWPE related to the wear performance of such systems. Unidirectional sliding tests against a 100Cr6 steel under dry conditions verified the significant potential of dispersed carbon nanofibres to reduce the wear rate of this polymer. In light of the promising results, a further optimization of the processing conditions of such UHMWPE nanocomposites is expected to yield interesting future nanocomposite materials even for demanding applications such as artificial knee implants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4173–4181, 2007     

Sodium dodecyl sulfate-assisted SILAR synthesis of nanostructured cadmium oxide films

Nanostructured CdO films were prepared on glass substrates by a surfactant – sodium dodecyl sulfate (SDS) – assisted SILAR technique. The influence of SDS concentrations of the growth solution on the structural, morphological and optical properties of the films was investigated and discussed. From the metallurgical microscope and scanning electron microscope images, it was seen that the surface morphology of the films are significantly enhanced by SDS addition. XRD investigations confirmed that the films have good crystallinity levels and are grown preferentially in (111) and (200) orientations. UV–vis. spectroscopy investigations showed that the bandgap and transmittance values of the films are affected dramatically by SDS concentrations.