Average Fiber Diameter Research Articles

Fabrication and characterization of electrospun porous cellulose acetate ultrathin fiber coatings incorporating essential oil

Bacterial adhesion has become a significant problem in industry and in the domestic domains due to causes loss of capital, labor, and energy worldwide. Microbial resistance to biocides and antimicrobials is a major concern, and several applications have been designed to prevent and inhibit bacterial adhesion. Therefore, there has recently been a demand for materials having antibacterial properties that contain active components which do not cause antibiotic resistance. Among them, integration of essential oils with micro/nano fibers as green and safe antimicrobial compounds was considered to have potential. For this reason, in this study, coatings containing St. John’s wort oil (SJWO) onto porous cellulose acetate ultrathin fiber (pCA_UF) were produced and the antibacterial and antifouling activities were evaluated. The average fiber diameter of 1356.37 ± 496.89 µm and the pore diameters of 413.91 ± 173.52 µm analyzed by scanning electron microscopy (SEM). In addition, the thickness of the coatings was found as 226 ± 35 µm. Attenuated Fourier-transform infrared (ATR-FTIR) indicated a physical type of interaction between SJWO and pCA_UF. Contact angle (CA) results confirmed the presence of SJWO on the pCA_UF decreased the hydrophobicity from 160 ± 16° to 74 ± 2°. pCA_UF-SJWO coatings showed a reduction in adherent bacteria such as Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, compared to the glass substrate and pCA_UF coatings. Overall, the data supports the use of ultrathin fiber with essential oil coatings for bacterial adhesion.

Preparation and characterization of edible pullulan/pectin nanofiber substrates and their digestion in simulated gastric and intestinal fluids

This article utilizes two ingestible substrates, pullulan and pectin, to fabricate nanofiber membranes by means of electrospinning technology, and assessed their digestion characteristics in simulated gastrointestinal fluids. The physicochemical properties of pullulan/pectin spinning solution and the effects of electrospinning process parameters on the diameter and morphology of pullulan/pectin nanofibers were investigated. Scanning electron microscope indicates that the best electrospinning process parameters were obtained as spinning voltage: 20 kV, needle-collector distance: 15 cm, propulsion speed: 0.6 mL/h and needle inner diameter: 0.41 mm. Moreover, at a pullulan/pectin volume ratio of 8:2, the nanofiber morphology exhibited optimal characteristics, featuring an average fiber diameter of 369.45 ± 42.41 nm. Fourier transform infrared spectroscopy, X-ray diffraction, and thermal analysis indicates the formation of strong hydrogen bonds between pullulan and pectin. The mechanical performance tests demonstrated that, with a volume ratio of 8:2 for pullulan and pectin, the nanofiber exhibited a tensile strength of 1196.86 ± 51.87 cN and an elongation at break of 80.26 ± 3.6%, indicating favorable capacity for elongation and deformation. Furthermore, the in vitro degradability test indicates that pullulan/pectin nanofibers with a volume ratio of 8:2 were decomposed by specific enzymes in intestinal fluid. Therefore, ingestible pullulan/pectin nanofiber substrates have shown certain development potential in the field of targeted drug or bioactive delivery.

Development of Active Antibacterial CEO/CS@PLA Nonwovens and the Application on Food Preservation.

The biodegradable activity antibacterial materials have been widely applied on food preservation because they not only protect foods from pathogenic attacks but also relieve environmental pollution. Biodegradable melt-blown nonwovens (MB) have several advantages over the other materials in terms of a simpler and more environmentally friendly fabrication process, higher specific surface area, and lower cost. Herein, polylactic acid (PLA) MB is first modified by polydopamine (PDA) to activate the surface. Then, chitosan (CS) and cinnamon essential oil (CEO) are used to decorate the surface of the modified PLA MB via a simple one-pot method to prepare CEO/CS@PLA MB with different CEO contents. Compared with PLA MB, CEO/CS@PLA MB had a rougher surface and larger average fiber diameter, while the average pore diameter and air permeability reduced. The input of CEO led to a decrease in the tensile strength of CEO/CS@PLA MB and an obvious increase in the elongation at break. The combination of CS and CEO shows excellent synergistic antibacterial effect. The antibacterial efficiencies of CEO/CS@PLA MB against Escherichia coli and Staphylococcus aureus enhance with the increase of the CEO content. When the weight ratio of CS to CEO is 1:2, the antibacterial efficiencies of CEO2/CS@PLA MB against E. coli and S. aureus are 99.98 and 99.99%, respectively. When being applied to the preservation of fresh strawberry, CEO2/CS@PLA MB can effectively inhibit the microbial growth in strawberry and reduce decay, which extends the shelf time of strawberry.

Ethanol-mediated electrospinning of casein-only bead-free nanofibers

Fabrication of electrospun nanofibers by blending casein with electrospinnable polymers and/or additives is well reported. However, the electrospinnablility of pure casein has not been described due to the tendency of casein proteins to self-aggregate and form large colloidal structures. Here we analyze the influence of pH, ethanol content, ionic environment, and casein concentration on the solubility, solution viscosity, surface tension, and conductivity of casein-based spinning dopes. Further, the influence of casein dope characteristics on our ability to electrospin bead-free nanofibers was evaluated. A homogenous dispersion of casein was observed for mixtures with 20 wt % casein prepared using 60 % ethanol/water mixture at pHeth 10. A minimum number of bead defects (BN, 6 × 10−3/μm2) and bead area (BA, 8.7 × 10−2) with minimum average fiber diameter (FD, 424 nm) and porosity (52 %) were observed for casein fibers fabricated using dopes containing 2 wt % of tetrasodium pyrophosphate (TSPP) on a casein basis. Further, the viscosity dependence on casein concentration at constant relative TSPP content was like that expected for a polyelectrolyte, and bead-free nanofibers were obtained at a concentration ∼2.5 times the entanglement concentration (Ce). Our results indicate that micellar dissociation is a necessary condition for the electrospinning of casein-only fibers free of beads and other polymers to fabricate novel biodegradable, and biocompatible, casein-based nanostructured mats, with the potential for food, cosmetic, packaging, and biomedical applications.

Preparation of silicon-nitride ceramic fibers with hafnium compounds loaded on the surface and the high temperature properties

The surface and core are composed of heterogeneous fiber materials that are endowed with excellent properties due to the unique structure. In this work, polysiloxane (PSZ) was used as the ceramic precursor and hafnium carbide (HfC) was used as the hafnium source, and Si–N–C–O-Hf hybridized ceramic fibers were obtained using electrostatic spinning and pyrolysis. After the primary fibers were pyrolyzed at 1400 °C, hemispherical particles were found on the surface of the ceramic fibers. And the average fiber diameters were around 3 μm. Thermogravimetric analysis (TGA) showed that the mass of the cured fibers decreased to 67 % below 1650 °C in an argon atmosphere. The mass of the ceramic fibers remained almost unchanged in the high temperature aerobic environment. Meanwhile, the thermal conductivity of the specimens has remained relatively low. Analytical tests confirmed that the hafnium-containing hemispherical protective layer gave the specimens excellent thermal stability, oxidation resistance, and high temperature insulation. In addition, the excellent mechanical properties make it suitable for a wide range of applications. The optimized high-temperature performance and mechanical properties indicate that metal-hybridized silicon-based ceramic fibers herein are suitable for ultra-high-temperature environments.

Upcycling spent coffee grounds and waste PET bottles into electrospun composite nanofiber mats for oil structuring applications

Spent coffee grounds (SCG) and post-consumer PET bottles (PETbot) are major waste materials from the food industry. In this work, their use to obtain electrospun composite nanofibers is explored aiming to develop a new route for their upcycling into high added-value oil-based products. Raising the proportion of PETbot increased the average fiber diameter (from 0.36 to 0.89 μm) and enhanced the tensile properties of the mats. Young's modulus and strain-at-break increased from 5.1 to 32.8 MPa and from 13.8 to 39.4 %, respectively, as the SGC:PETbot weight ratio decreased. Dispersions of the mats in castor oil exhibited shear-thinning and gel-like viscoelastic properties which can be tuned through the SCG:PETbot ratio. Friction coefficient values of resulting oleogels tested in a tribological contact ranged from 0.165 to 0.092. SCG and PETbot can be used to obtain electrospun nanofibers with oil structuring capabilities while resulting oleogels are proposed as environmentally-friendly alternatives to semisolid lubricants.

Electrospun starch-based nanofiber mats for odor adsorption of oyster peptides: Recyclability and structural characterization

The off-odor of seafood, which negatively affected its flavor and quality, was removed mainly by non-recyclable liquid-phase deodorization methods at present. In this work, octenylsuccinylated starch (OSS)-pullulan (PUL) nanofiber mats were regenerated after physical adsorption and thermal desorption of off-odor compounds in oyster peptides. The mat structure was characterized and the adsorption process was investigated. The regenerated nanofiber mats maintained a favorable appearance and microscopic morphology even after 25 adsorption-desorption cycles, with a reduction in average fiber diameter and average pore area, an increase in hydrophobicity and alterations in surface groups. Their adsorption rate first decreased and then stabilized as the number of cycles increased and was as high as 81.76% after 25 cycles. Correlation analysis revealed that the adsorption efficiency of regenerated nanofiber mats was related to their microstructure, surface groups and hydrophobicity. These findings could provide a theoretical basis for odor removal by electrospun nanofiber mats and their recycling.

Electrospinning of smart nanofibers based on PVP/PDA for wound dressing applications

In the present study, electrospinning of polyvinylpyrrolidone (PVP) and polydiacetylene (PDA) with pomegranate peel (PG) extract was investigated for the preparation of smart and antibacterial nanofibers. Briefly, PDA-PVP solutions were firstly prepared at two different ratios and electrospun under different conditions. Based on the SEM results, the 1:3 ratio of PDA:PVP nanofibers, with an average fiber diameter of 130 ± 40 nm, electrospun at a voltage of 15 kV, feeding rate of 0.5 ml/h and collector distance of 15 cm was selected as the optimal conditions. The addition of PG resulted in an increase in the diameter of the fibers. The color of the electrospun fibers was altered from blue to red due to changes in either temperature or pH or exposure to different solvents. The antibacterial test showed high antimicrobial activity of the fibers loaded with PG extract against both S. aureus and E. coli. MTT assay and cell attachment also validated the biocompatibility of the fabricated nanofibers. Thus, the prepared smart PG-loaded nanofibers had a high potential to be used in wound dressing applications.

Effect of PLGA Concentration in Electrospinning Solution on Biocompatibility, Morphology and Mechanical Properties of Nonwoven Scaffolds

In this work, the effects of weight concentration on the properties of poly(lactide-co-glycolide) polymeric scaffolds prepared by electrospinning are investigated, using four different weight concentrations of poly(lactide-co-glycolide) for the electrospinning solutions (2, 3, 4, 5 wt.%). With increasing concentration of poly(lactide-co-glycolide) in the electrospinning solutions, their viscosity increases significantly. The average fiber diameter of the scaffolds also increases with increasing concentration. Moreover, the tensile strength and maximum elongation at break of the scaffold increase with increasing electrospinning concentration. The prepared scaffolds have hydrophobic properties and their wetting angle does not change with the concentration of the electrospinning solution. All poly(lactide-co-glycolide) scaffolds are non-toxic toward fibroblasts of the cell line 3T3-L1, with the highest numbers of cells observed on the surface of scaffolds prepared from the 2-, 3- and 4-wt.% electrospinning solutions. The results of the analysis of mechanical and biological properties indicate that the poly(lactide-co-glycolide) scaffolds prepared from the 4 wt.% electrospinning solution have optimal properties for future applications in skin tissue engineering. This is due to the fact that the poly(lactide-co-glycolide) scaffolds prepared from the 2 wt.% and 3 wt.% electrospinning solution exhibit low mechanical properties, and 5 wt.% have the lowest porosity values, which might be the cause of their lowest biological properties.

Micromechanical analysis of composite materials considering material variability and microvoids

One of the main challenges for fiber-reinforced polymers (FRP) is the difficulty to predict their mechanical behavior. At the microscale, the properties of the constituents, their spatial distribution and the defects arising from manufacturing affect the mechanical behavior. In this work, statistically representative volume elements (SRVEs) are proposed based on a micromechanical finite element model to determine the effect of content, distribution and size of microstructural defects and, material uncertainties on the elastic mesoscale properties of FRPs. To that end, different cylindrical void sizes are considered as well as irregular shaped voids between fiber tows (inter-fiber voids). Fibers and voids are randomly distributed in a SRVE. An uncertainty quantification and management analysis is employed to obtain statistical descriptors of the effective mesoscale mechanical properties of FRPs. The results obtained are compared with analytical models. It is demonstrated that, for carbon fiber/epoxy composites, SRVEs with lateral dimensions equivalent to 15 times the average fiber diameter and a length of 0.01 mm along the longitudinal direction remain statistically representative with or without the presence of voids. The results show that the presence of voids reduces the transverse and shear elastic properties of FRPs. The smaller the voids are, the bigger is the reduction. Regarding the presence of inter-fiber voids, the reduction is lower. This trend is well predicted by the Mori–Tanaka mean field theory. However, the relative difference between the numerical and the analytical predictions increases for high void volume fractions. Regarding the effective longitudinal Young’s modulus, the rule of mixtures, the Mori–Tanaka mean field theory and the concentric cylinder assembly model provide similar predictions for the mean value, but the uncertainty is overestimated by the analytical models because the properties of the fibers take a single value for each calculation with the analytical model, while they more realistically change from fiber to fiber in the numerical SRVEs.

Production of Ultrafine PVDF Nanofiber-/Nanonet-Based Air Filters via the Electroblowing Technique by Employing PEG as a Pore-Forming Agent.

Particles with diameters smaller than 2.5 μm (PM2.5) can penetrate the respiratory system and have negative impacts on human health. Filter media with a porous surface and nanofiber/nanonet structure demonstrate superior filtration performance compared to traditional nano- and microfiber-based filters. In this study, nanostructured filters were produced using the electroblowing method from solutions containing different ratios of poly(vinylidene fluoride) (PVDF) and polyethylene glycol (PEG) polymers for the first time. By increasing the water-soluble PEG ratio in PVDF/PEG blend nanofibers and employing a water bath treatment to the produced mat afterward, a more porous fibrous structure was obtained with a lower average fiber diameter. Notably, the removal of PEG from the PVDF/PEG (3-7) sample, which had the highest PEG content, exhibited clustered nanofiber-/nanonet-like structures with average diameters of 170 and 50 nm at the points where the fibers intersect. Although this process resulted in a slight decrease in the filtration efficiency (-1.3%), the significant reduction observed in pressure drop led to a 3.2% increase in the quality factor (QF). Additionally, by exploiting the polarizability of PVDF under an electric field, the filtration efficiency of the nanostructured PVDF filters enhanced with a ratio of 3.6% after corona discharge treatment leading to a 60% improvement in the QF. As a result, the PVDF/PEG (3-7) sample presented an impressive filtration efficiency of 99.57%, a pressure drop (ΔP) of 158 Pa, and a QF of 0.0345 Pa-1.

Influence of Rheological and Morphological Characteristics of Polyhydroxybutyrate on Its Meltblown Process Behavior.

Polyhydroxybutyrate (PHB) is a promising biopolymer. However, processing PHB in pure form in thermoplastic processes is limited due to its rapid degradation, very low initial crystallization rate, strong post-crystallization, and its low final stretchability. In this article, we screened commercial PHBs for morphological characteristics, rheological properties, and "performance" in the meltblown process in order to reveal process-relevant properties and overcome the shortcoming of PHB in thermoplastic processes for fiber formation. An evaluation of degradation (extruded (meltblown) material vs. granules) was performed via rheological and SEC analysis. The study revealed large differences in the minimum melt temperature (175 up to 200 °C) and the grade-dependent limitation of accessible throughput on a 500 mm plant. The average fiber diameter could be lowered from around 10 μm to 2.4 μm in median, which are the finest reported values in the literature so far. It was found that the determination of the necessary process temperature can be predicted well from the complex shear viscosity. Different to expectations, it became apparent that a broader initial molar mass distribution (>8) is suitable to overcome the state-of-the art limitations of PHAs in order to stabilize fiber formation, increase the productivity, and obtain better resistance towards thermal degradation in process. Accordingly, longer polymer chain fractions could be more affected by degradation than medium and short polymer chains in the distribution. Further, a low initial narrow distributed molar mass resulted in too brittle fabrics.

Evaluation of the Wool Production on Romanian Sheep Breeds

Abstract Sheep breeding is a traditional activity in Romania and wool production has been for a long period the main resource for the farmers’ prosperity. The opportunity of this study was generated by two main aspects: the change of the exploitation directions of sheep towards milk and meat production, which contributed to the lack of interest in selection and breeding for wool and to the reduction of the productive level and quality parameters of the wool; the absence of a national standard for classifying raw wool adapted to the current breeds structure, the conditions of sheep farming and the market requirements for this animal product An extensive study was carried out over 5 years on flocks of sheep belonging to the main local breeds Merinos de Palas, Tsigaie, Tsurcana, the newly created breeds at ICDCOC Palas Constanta respective Palas Meat Breed, Palas Milk Breed, Palas Prolific Breed as well as on some hybrids obtained through crossbreeding of new breeds with imported sheep breeds specialised for meat production (Texel and Rouge de l’ Ouest). The main goals of this study were: to establish the average level of wool production, the limits of variation and the potential for selection for wool quantity, by individual weighing of the wool fleeces harvested during the shearing season; to evaluate the wool quality level in the flocks analysed on the basis of the objective determination, by laboratory analysis on randomly collected samples, of the average fibre diameter, relative length of the staples, individual fibre length, degree of crimp, degree of impurity and the limits of variation of these quality parameters. This paper presents a summary of the values obtained for the quantity of raw wool and the fineness of wool as an essential quality parameter for the classification and valorisation of this natural resource. The results obtained in the study revealed in general a large variability in the productivity level of local sheep breeds and their hybrids with specialised imported breeds. The existence in the analysed herds of a percentage of 40-50 % of sheep performing above the flocks average (plusvariants) shows a potential for selection for the quantitative level of wool production. Thus, for these selected flocks (lines) an additional 10.23 ≈ 24.09 % wool production can be obtained compared to the averages levels. In terms of average fineness the analysis of the data shows that : the Palas Merino sheep, fall into the category of fine wool breeds; the three new sheep breeds created at ICDCOC Palas and the Tsigaie breed belonging to the Reghin - Mures Experimental Base have semi-fine wool (fiber diameter over 25 microns); the flock of White Tsurcana breed from the Bilciuresti - Dambovita Experimental Base falls into the category of sheep with semi coarse - coarse wool. The range of variation in diameter was very wide for all the breeds analysed. Thus in the Palas Merino breed differences of 5-7.5 μm between the maximum and minimum diameter measured represent according to the Bradford classification (English system) a difference of 7 fineness classes . The Tsigai breed has also a large uneveness of this parameter, CV over 20 % in rams and sheep yearlings. The analysis of the data on wool diameter revealed that more than 40% of the studied sheeps had above-average fineness, they could constitute selected flocks (lines) with higher values of the main wool quality parameter that determines the market value. Thus an increase in wool fineness of 3.63 ≈ 11.52 % can be achieved within a selected flock . The results presented showed that, under the current conditions of breeding and exploitation of sheep in the analized flocks, there is a potential of selection for wool production and for fibre diameter as the main quality parameter . Also, on the basis of the analysis carried out on the grading/classing/sorting of wool worldwide and the results obtained within this study, proposals were made to improve the quantity and increase the commercial value of wool production obtained from the sheep breeds reared in Romania.

Investigation of Basic Characteristics of Waterproof-Breathable Nonwoven Nano-Fabric Manufactured by Improved Melt-Blowing Method

In recent years, materials with both waterproof and breathability have also been marked with the eye-catching slogan of "waterproof-breathable" on the commodity such as personal protective equipment or sportswear. Regarding the application of nanofiber non-woven fabric as waterproof and breathable materials for functional textile, although there are previous reports regarding conventional micro-fabrics, the relationship between the compositions of the fiber aggregate, waterproof and breathable properties remain unclear regarding nanofabrics. Therefore, this study shows investigation of influence of fiber diameter, bulk density and thickness of the woven nanofabric on waterproof-breathable ability with experiment and CFD (computational fluid dynamics) model. As a result, the average fiber diameters, bulk densities, and thicknesses to achieve waterproofness and air permeability were numerically obtained respectively. From the results, it can be found that, these parameters can be used as a reference for manufacturing high-performance waterproof permeable materials with both high waterproofness and high air permeability.

Synergistic properties of polysuccinimide/poly(lactic acid) co-electrospun and blended-electrospun nanofibers

One of the greatest challenges in tissue engineering and tissue scaffold development is tissue integration. If cells cannot adhere, infiltrate, and migrate through the implant, the immune system will develop a fibrous capsule around it, isolating it, and rendering it useless. To solve this complex issue, researchers directed their attention towards blend and composite materials. Poly(lactic acid) PLA is a popular polymer used for biomedical applications having several advantages such biocompatibility, chemical stability, and cost-effectiveness. Concurrently, hydrophobicity, poor cell adhesion, and slow biodegradation limit application possibilities. On the other hand, polysuccinimide (PSI) is versatile polymer with excellent cell adhesion, biocompatibility, and a fast biodegradation. The objective of this work is to develop electrospun meshes composed of a fast (PSI) and slow (PLA) degrading component. The fabricated blend-electrospun meshes have a pronounced 3D structure compared to the co-electrospun meshes. Average fibre diameters were 580 ± 140 and 650 ± 110 nm for the co-electrospun and blend-electrospun meshes then after cross-linking the meshes diameters increased to 890 ± 300 and 750 ± 150 nm respectively. Both meshes exhibited increased hydrophilicity compared to pure PLA meshes (125°) especially after the cross-linking (Co-spun: 119°, Blend-spun: 78°). The co-electrospun PSI/PLA demonstrated an increased specific loading capacity suggesting a synergistic relationship between the two polymer fibres. In contrast however, the blend mesh performed poorly. The in vitro degradation assessment confirmed that the PSI component degrades in under a week while the PLA component of the composite was still stable even after 4 weeks. To conclude, both meshes have their own advantages which could be exploited for different applications.

Effect of pole piece structure on magnetic lens electrospinning system: Experimental and simulation study

Magnetic lenses can effectively reduce the fiber diameter and whipping-circle width to control the random behavior of electrospinning. Although the axisymmetric magnetic lens for electrostatic spinning have several potential applications, the effect of its pole-piece structure on the electrostatic spinning process has not been adequately discussed. In this study, we explored the influence of changing the pole piece structure of the magnetic lens on the electrospinning process using experimental and numerical simulation methods. The results showed that for a 12 wt% polyacrylonitrile (PAN) solution, when the applied voltage was 15 kV, the feed rate was 1 mL/h, and current of the magnetic lens was 1 A, the gap width of the magnetic lens had a notable effect on the fiber deposition efficiency of the electrostatic spinning range of the magnetic lens. Appropriately reducing the gap width in the range of 1–10 mm can effectively reduce the deposition range of the fibers and improve fiber film thickness. Furthermore, when the angle of α is 45°, it exerts the most significant effect on the electrostatic spinning spray range and deposition efficiency, and the fiber film thickness and average fiber diameter attain their highest values. When the angle of α increases or decreases from 45°, the fiber film thickness and fiber diameter both show a decreasing trend. A change in the magnetic lens structure can effectively change the ejection range and fiber diameter during electrostatic spinning, which shows great potential in the field of nanofiber production.

Antifungal Activity of Chitosan/Poly(Ethylene Oxide) Blend Electrospun Polymeric Fiber Mat Doped with Metallic Silver Nanoparticles.

In this work, the implementation of advanced functional coatings based on the combination of two compatible nanofabrication techniques such as electrospinning and dip-coating technology have been successfully obtained for the design of antifungal surfaces. In a first step, uniform and beadless electrospun nanofibers of both polyethylene oxide (PEO) and polyethylene (PEO)/chitosan (CS) blend samples have been obtained. In a second step, the dip-coating process has been gradually performed in order to ensure an adequate distribution of silver nanoparticles (AgNPs) within the electrospun polymeric matrix (PEO/CS/AgNPs) by using a chemical reduction synthetic process, denoted as in situ synthesis (ISS). Scanning electron microscopy (SEM) has been used to evaluate the surface morphology of the samples, showing an evolution in average fiber diameter from 157 ± 43 nm (PEO), 124 ± 36 nm (PEO/CS) and 330 ± 106 nm (PEO/CS/AgNPs). Atomic force microscopy (AFM) has been used to evaluate the roughness profile of the samples, indicating that the ISS process induced a smooth roughness surface because a change in the average roughness Ra from 84.5 nm (PEO/CS) up to 38.9 nm (PEO/CS/AgNPs) was observed. The presence of AgNPs within the electrospun fiber mat has been corroborated by UV-Vis spectroscopy thanks to their characteristic optical properties (orange film coloration) associated to the Localized Surface Plasmon Resonance (LSPR) phenomenon by showing an intense absorption band in the visible region at 436 nm. Energy dispersive X-ray (EDX) profile also indicates the existence of a peak located at 3 keV associated to silver. In addition, after doping the electrospun nanofibers with AgNPs, an important change in the wettability with an intrinsic hydrophobic behavior was observed by showing an evolution in the water contact angle value from 23.4° ± 1.3 (PEO/CS) up to 97.7° ± 5.3 (PEO/CS/AgNPs). The evaluation of the antifungal activity of the nanofibrous mats against Pleurotus ostreatus clearly indicates that the presence of AgNPs in the outer surface of the nanofibers produced an important enhancement in the inhibition zone during mycelium growth as well as a better antifungal efficacy after a longer exposure time. Finally, these fabricated electrospun nanofibrous membranes can offer a wide range of potential uses in fields as diverse as biomedicine (antimicrobial against human or plant pathogen fungi) or even in the design of innovative packaging materials for food preservation.

Prolonged and Controllable Release of Doxorubicin Hydrochloride from the Composite Electrospun Poly(ε-Caprolactone)/Polyvinylpyrrolidone Scaffolds

Burst release, typical for the drug-loaded electrospun poly(ε-caprolactone) (PCL) scaffolds is unfavorable in case of cytostatics due to the toxic levels reached during the initial implantation period. In the present short communication, we report an unexpected ability of the composite scaffolds made of PCL and water-soluble polyvinylpyrrolidone (PVP) to provide long-term release of widely used anti-cancer drug doxorubicin hydrochloride (DOX-HCl). That effect was observed for electrospun DOX-HCl-loaded composite scaffolds based on PCL and PVP with various mass ratios (100/0, 95/5, 90/10, 75/25 and 50/50). After the morphology and water contact angle studies, it was concluded that PVP content has no effect on the average fiber diameter, while PVP content higher 10 wt. % changes the hydrophobic character of the scaffolds surface (water contact angle of 123.9 ± 3.5°) to superhydrophilic (water contact angle of 0°). Despite the dramatic change in water wettability, by high performance liquid chromatography (HPLC), it was revealed that the PVP content in the scaffolds reduces the DOX-HCl release rate under short (first hours) and long-term (during 1 month) exposure to phosphate buffer saline (PBS). These results are in good agreement with in vitro studies, in which the viability of HeLa cervical cancer cells was higher after 24 h of culture with scaffolds with high PVP content.

Flexible centrifugally spun PVP based SnO2@carbon nanofiber electrodes

Sodium-ion batteries (SIBs) have attracted significant attention because of the abundant resource and low-cost of sodium. Furthermore, flexible and wearable functional electronics have been presented as one of the most important emerging technology. Carbon nanofibers are promising candidates for flexible electrodes due to their high electronic conductivity and high surface area, while it is vital to use non-petroleum-based polymers considering environmental concerns. Developing flexible nanostructured electrodes by using environment friendly polymers with a fast and low-cost technique is critical to develop high performance flexible electronics. Electrochemical properties are influenced by the morphology and average fiber diameters of nanofibers. In this study, poly(vinylpyrrolidone) (PVP) solutions with various concentrations and two different solvent systems (ethanol/water and ethanol/dimethylformamide) were successfully spun into nanofibers by the fast, safe, low-cost, and environment friendly technique of centrifugal spinning. The effect of solvent system and solution concentration was investigated by using scanning electron microscopy images, and the average fiber diameters varied from 436 nm to 3 µm. Moreover, nine different heat treatments were studied, and the effect of time and temperature during stabilization and carbonization on the morphology of carbon nanofibers (CNFs) was investigated. Furthermore, flexible carbon nanofibers were fabricated and used as binder-free anodes in sodium-ion batteries. In order to enhance the electrochemical properties of flexible CNFs, flexible SnO2@CNFs were fabricated by combining centrifugal spinning and heat treatment. The electrochemical performance of the flexible SnO2@carbon nanofiber anodes was evaluated by conducting galvanostatic charge/discharge tests and cycling voltammetry. A high rate of performance was also presented. The high reversible capacity of 400 mA h/g was delivered when flexible centrifugally spun PVP based SnO2@carbon nanofiber electrodes were used in SIBs.

Electrospun nanofiber composite mat based on ulvan for wound dressing applications

Wound dressings can be used to create a temporary healing environment and expedite the wound healing process. Ulvan (ULV) is a sulfated polysaccharide with potent antiviral and anti-inflammatory activities. Polycaprolactone (PCL) is a hydrophobic biodegradable polyester that exhibits slow degradation, strong mechanical strength, and excellent biocompatibility. Electrospun nanofiber matrices mimic the microstructure of the extracellular matrix, allowing them to promote cell proliferation and differentiation. Therefore, the primary objective of this study was to fabricate a polycaprolactone-ulvan fibrous composite mat (PCL-ULV) using the electrospinning technique and to investigate its physical and chemical properties. To assess the characteristics of PCL-ULV, scanning electron microscopy (SEM) was utilized to examine its morphology and diameter distribution. Fourier transform infrared (FTIR) spectroscopy, calcofluor white staining, and monosaccharide analysis were employed to analyze the components of PCL-ULV. Additionally, the water contact angle was measured to evaluate the hydrophilicity. Furthermore, the proliferation and morphology of and gene expression in NIH3T3 fibroblasts on PCL-ULV were assessed. The results showed that the average PCL-ULV fiber diameter was significantly smaller than that of the PCL fibers. The water contact angle measurements indicated that PCL-ULV exhibited better hydrophilicity than the PCL mat. FTIR, calcofluor white staining, and monosaccharide analyses demonstrated that ULV could be successfully coelectrospun with PCL. NIH3T3 fibroblasts cultured on PCL and PCL-ULV showed different cellular behaviors. On PCL-ULV, cell adhesion, proliferation, and stretching were greater than those on PCL. Moreover, the behavior of NIH3T3 fibroblasts on PCL and PCL-ULV differed, as the cells on PCL-ULV exhibited higher proliferation and more stretching. Furthermore, NIH3T3 fibroblasts cultured on ULV-PCL showed higher α-SMA and MMP-9 gene expression and a lower ratio of TIMP-1/MMP-9 than those cultured on PCL. Notably, scarless wounds display lower TIMP/MMP expression ratios than scarring wounds. Thus, the fibrous composite mat PCL-ULV shows potential as a wound dressing for scarless wound healing.