جستجوی مقالات مرتبط با کلیدواژه « nanofibers » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

The use of nano fibers has grown significantly in recent years. These fibers have many advantages over micro fibers, the most important of which is their specific surface area and greater strength. Electrospinning is a conventional process used to prepare fine and uniform polymer nanofibers. The use of this method is limited due to the need for a high potential difference, the need for an electrically conductive collector, and relatively low production speed. Centrifugal spinning technology uses centrifugal force instead of using high voltage to produce nanofiber polymer and is a safer and more affordable option than electrospinning. In this study, centrifugal and electric forces were used simultaneously to produce polyacrylonitrile nanofibers and the effectS of adding centrifugal force to electric forces on the diameter of nanofibers, production rate, percentage of surface porosity, and dye absorption of polyacrylonitrile nanofibers were compared for both methods. The results showed that the use of electrocentrifuge instead of electrospinning can reduce the diameter of nanofibers by 40% and increase the production rate by 68%. On the other hand, increasing the rotation speed in this method leads to a decrease in the diameter of nanofibers and an increase in the specific surface area. Morever, nanofibers produced by this method were 33% more successful than electrospun nanofibers in absorbing colored pollutants. Therefore, the use of these fibers as an effective absorbent for colored wastes is suggested.

In this study, chitosan-based nanofibrous scaffold containing hydroxyapatite/metal-organic framework (HAp@MOF) nanocomposite was prepared for potential application in tissue engineering. First, HAp@MOF nanocomposite was produced and characterized by in-situ synthesis of metal-organic framework, and then chitosan nanofibrous scaffold was produced using electrospinning method. Morphology, crystal structure, hydrophilic behavior and antibacterial activity of CS/PVA-HAp@MOF composite nanofibrous scaffold were studied and evaluated. For this purpose, scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, water contact angle and disk diffusion test were used. The investigation of the morphology of the composite nanofibrous scaffold showed the production of uniform and bead-free nanofibers with an average diameter of 113 nm. Also, the addition of HAp@MOF nanocomposite has increased the diameter of the fabricated fibers and increased the hydrophilic property with a contact angle of 57 degrees. Moreover, the investigations of antibacterial activity of nanofibrous scaffolds have indicated the appropriate performance of the nanofibrous scaffold containing HAp@MOF nanocomposite against the gram-positive bacteria Staphylococcus aureus and the gram-negative bacteria Escherichia coli. The obtained results showed that CS/PVA-HAp@MOF composite nanofibrous scaffold can be used as a good candidate for potential tissue engineering applications.

The skin, as the first defense barrier against the entry of pathogens into the body, helps to heal the wounds through four stages including homeostasis, inflammation, proliferation, and regeneration. Today, various wound dressings have been introduced to help the body's immune system to improve the speed and quality of wound healing. Conventional wound dressings include polyurethane foams and elastomers, hydrocolloids, hydrogels, semipermeable films, alginate wound dressings, and electrospun polymer nanofibers. Wound dressings based on polymer nanofibers have received a lot of attention for reasons such as similarity to the extracellular matrix (ECM), the desired cell adhesion, high surface-to-volume ratio, gas exchange capability, nutrient supply, and fluid evaporation control. So far, the use of electrospun polyurethanes for the preparation of wound dressings has been reported in various studies. However, the results of studies on a wide range of wound dressings have shown that almost no polymer alone can heal different wounds, effectively. For this reason, many efforts have been made recently to develop polyurethane wound dressings to heal various types of wounds. In this regard, natural polymers have been used due to properties such as biological activity, biocompatibility, and biodegradability along with polyurethanes with desirable physical and mechanical properties. In this article, after introducing the the mechanism of wound healing and describing the characteristics of an ideal wound dressing, the polyurethane/natural polymer blends nanofibers for use as electrospun wound dressings will be discussed.

In this research work, the ability to use nanofibrous membrane as an absorbent filter was investigated. For this purpose, electrospinning of polyamide 6 (PA6) in formic acid was performed at different concentrations and the effect of polymer concentration, voltage and needle-to-tip distance on the morphology of the fibers was evaluated using the statistical method of response surface methodology (RSM). Based on the results of the statistical analysis, the optimal sample was selected with the minimum average fiber diameter (111 nm) at a concentration of 10% PA6, a voltage of 20 KV and a distance of 20 cm. Then, the effect of carbon nanotubes (CNT) incorporation into the fibers (at different percentages of 0.1, 0.2, and 0.5%wt) was studied. The porosity test showed an increase in the porosity of the samples with the addition of CNT. The results of the tensile test revealed that the maximum tensile strength and elongation up to the breaking point were obtained for the fibers containing 0.1% CNT. FTIR spectra depicted the characteristic peaks of amides and amine groups in PA6. Thermal analysis (TGA) showed that thermal stability increased with the addition of CNT. Finally, in the spectrophotometric test, the absorption of dye by the nanofibrous membrane was observed by prolonging time.

The behaviors of biological scaffolds from the attack of their mechanical behavior are a function of their microstructure. In this research,an attempt is made to find the relationship between the microstructure and mechanical properties of the studied scaffolds. Therefore, electrospinning of 10% polyvinyl alcohol and 20% gum arabic solution was performed in different ratios (60-40, 30-70, 20-80, 10-90, 0-100), and the effect of gum arabic on physical properties, microstructure, and properties. The mechanical nature of the spun scaffolding was investigated. The structural properties of the solution and the association between its phases were investigated using a light microscope.The viscosity of the solution was also investigated to investigate the effect of gum arabic on the electrospinning process. Fourier transform infrared spectroscopy of production scaffolds was performed to investigate the presence of gum arabic in the structure of electrified fibers. A tensile test was used to evaluate the mechanical properties of production scaffolds. The results showed that the presence of gum arabic causes the production of thinner fibers with higher density in the scaffolds and as a result of these changes, the modulus and strength of biological scaffolds increase.

Electrospun nanofibers are a suitable substrate for loading a variety of drugs and extracts due to their controllable properties. In this study, chamomile extract was loaded as an antibacterial agent in polycaprolactone-polyethylene glycol nanofibers. For this purpose, 3: 2, 1: 1 and 2: 3 weight ratio of polycaprolactone-polyethylene glycol solutions were prepared and chamomile extract (7%) was added to the optimal composition and then electrospun. Morphology, cell compatibility, cytotoxicity, extract release and antibacterial properties of the resulting web were examined. Electron microscopy (SEM) images show a suitable and bead-less morphology for nanofiber PCL: PEG (2: 3) containing an extract with an average diameter of 211 ±70 nm. Interactions between the functional groups of polycaprolactone and polyethylene glycol and chamomile extract are observed in the FTIR spectra. The results of cell culture test indicate proper growth and proliferation of fibroblast cells on both chamomile extract loaded and non-loaded nanofibers. The results of MTT test, although confirming the non-toxicity of both extract loaded and non-loaded nanofibers, but the percentage of cell survival was higher on the sample containing chamomile extract. The results of antibacterial test confirm the antibacterial activities of polycaprolactone-polyethylene glycol nanofibers containing chamomile extract against both gram-positive and gram-negative bacteria.

In today's advanced world, due to the expansion of industries and the use of machinery in factories, noise has become an inevitable part of life. This caused man to pay more attention to the sense of hearing and to study acoustics among the basic subjects. One of the methods to control noise pollution is the method of absorbing sound waves. In different acoustic designs, porous sound-absorbing materials have been considered. In this regard, textiles have been studied due to their ductility and Porosity. In this study, Warp Knitted Spacer Fabric(WKSF) was produced on a by double needle bar Rachel machine. Then, polyacrylonitrile (PAN) nanofibers were coated on (WKSF) by a single-nozzle electrospinning device with different electrospinning durations. The sound absorption of (WKSF) coated with PAN nanofibers was investigated by impedance tube method in the frequency band of 1000-5000 Hz. The experimental results showed that the coating of PAN nanofibers on (WKSF) increases the sound absorption coefficient at all frequencies.

In the present study, a membrane of polybutylene terephthalate doped with multi-walled carbon nanotubes was prepared by the electrospinning process of nanofibers. Electron microscopy images of the synthesized nanocomposite proved the homogeneous structure and porous surface of the film. The capability and efficiency of the prepared fibers were tested by studying the adsorption of 2-chloroethyl ethyl sulfide as a mustard gas-like compound. Parameters affecting the morphology of nanofibers such as polymer concentration and the amount of multi-walled carbon nanotubes were investigated and optimized. Important variables in the mustard gas adsorption process included: ion strength, adsorption time and temperature. For this purpose, multivariate modeling based on experimental design using central composite design and response -surface methodology was used to optimize the factors affecting the process. The removal efficiency was 96% at the time of absorption of 12 minutes and the adsorption temperature was 30 ° C and the initial concentration of mustard-like agent was 20 mg L-1. The results of adsorption isotherms showed that the adsorption process of 2-chloroethyl ethyl sulfide by developed nanofibers follows the model of Langmuir (R2 = 0.991) and Friendlich (R2 = 0.986). The results of this study showed that PBT / MWCNTs nanocomposite membrane have good efficiency in adsorption and entrapment of mustard-like agent 2-chloroethyl ethyl sulfide and can be used to develop coatings against these compounds.

Cartilage damages, including degenerative joint diseases, are a current medical‏ ‏problem. Once damaged, adult ‎human articular cartilage has a limited capacity‏ ‏for intrinsic repair. Tissue engineering is becoming promising for ‎cartilage‏ ‏repair. Nano fibers‏ ‏have considered as suitable candidates for improving the tissue engineering‏ ‏scaffold, ‎since they can mimic microarchitecture of tissue extracellular matrix, ‎perfectly. In this research, a biodegradable ‎nanofiber scaffold of 10% silk fibroin and 5% ‎chitosan solution with a ratio of 70-30 or 50-50 respectively, made by ‎electrospinning technique ‎for articular cartilage tissue engineering. By Scanning electron microscope imaging, ‎nanofibers morphology and average ‎diameter were determined. Fourier Transform Infrared spectroscopy was ‎performed to ‎investigate the functional groups of the scaffold surface. Mechanical properties of these ‎scaffolds were ‎determined by measuring of Young´s Module, Elongation at break and Breaking ‎tenacity. PBS buffer was used for ‎in-vitro degradation assay. Scanning electron microscope images analysis showed that ‎the fibers were bead-less with ‎uniform morphology with an average diameter of 148.8 ± 52.32‎‏ ‏and 138.5± 24.51 nm respectively for 70-30 and 50-‎‎50 scaffolds. After 12 weeks‎‏ ‏assay, the percentage of degradation for 70-30 and 50-50 scaffold respectively‎‏ ‏were ‎‎6.16 ± 0.9 and 6.82±0.7% of total scaffold weight. As a result, silk fibroin-chitosan nanofiber scaffolds due to ‎containing cell adhesion domains caused by‏ ‏their protein nature and because of their slow degradation, suitable ‎physical‏ ‏structure and mechanical properties are suitable candidates for articular‏ ‏cartilage repair.‎

The skin is the largest organ of the body, with a total area of about 20 square feet. ... The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone.The human skin is the outer covering of the body and is the largest organ of the integumentary system. The skin has up to seven layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organ. WOUND IS an injury to living tissue caused by a cut, blow, or other impact, typically one in which the skin is cut or broken. Novel wound dressings have practiced incessant and noteworthy variations as the earliest periods. The expansion begins with the usage of natural-materials to merely covering the wounds to the materials of the existing period that could be particularly manufactured to display numerous unexpected purposes. The modern bandage-materials constructed via bio-polymeric nano-fibers holding several active-compounds that are useful for the healing of wounds. With the correct selections of bio-polymers using for production of these nano-fibrous materials, they could improve the healing of wounds expressively compared with the conventional dressing materials, such as gauze. The novel wound dressings could be completed such that they have bio-active ingredients, for instance anti-microbial, anti-bacterial, and anti-inflammatory agents, which could be released to the wounds improving their healing. This review offers an overview of various kinds of wounds, operational factors in wound healing and different forms of wound dressing materials with a superior highlighting to those manufactured of nanofibers.

Diesel motors are used vastly as main sources of power in industry and transportation in modern countries. They are heavy-duty and their durability and simplicity makes them technically and economically handy. Diesel engines performance depends on clean fuel, mainly because of injection equipment and ultra-high pressure pumps. So, the most appropriate fuel conditioning equipment must be used. Polymeric filter media are usually used in diesel fuel filtration. Despite removing most of diesel impurities, they are unable to trap micron-size particulates. In addition, small water droplets coalescence is rarely possible. Electrospun Nano-fibrous Membranes (ENMs) are increasingly gaining momentum for their filtration efficiency in the last decade. Fineness and large surface area per unit volume of ENMs make them an effective method for particulate removal and purification. In this study, optimized ENMs were prepared and their filtration performance of micron-sized particulate matters and separation of water droplets from diesel fuel was investigated.

In this paper, polyacrylonitrile-nanopolyxomolybdate PAN-{Mo154} composite nanofibrous membrane was prepared by electrospinning under ambient conditions.  Nanofibers with an average fiber diameter of 100 nm were obtained under optimized conditions: 8wt.% of polyacrylonitrile, applied voltage of 12 kV, feed rate of 0.1 ml/h, nozzle to collector distance of 15 cm, and the collector rotating speed of 600 rpm. The structure of composite nanofibers was evaluated using SEM, TEM, FT-IR and UV-Vis techniques. The fabricated nanofibrous membrane was used for the adsorption of capsaicinoids. The maximum adsorption of capsaicinoids was obtained in about 30 minutes. The optimized nanofibrous membrane showed high efficiency 92-98% in adsorption of capsaicinoids.  These biocompatible, non-toxic nanofibrous membranes can be produced fast with low cost and they have high adsorption capacity for capsaicinoids. Thus, they can be used in protective clothing and respiratory masks.

 Based on previous studies, among all drug delivery systems, polymeric nanofibers have been used extensively. Release mechanism and rate can be tuned by changing polymer concentration, size and shape of nanofibers. In the present study, a drug delivery system was prepared by natural polymers of gum tragacanth and gelatin using electrospinning method for control delivery of imipenem/cilastatin in antibacterial applications. Nanofibers' diameters and morphology were measured by scanning electron microscopy (SEM). The physicochemical properties of nanofibers' materials were analyzed by Fourier transform infrared spectroscopy (FTIR). In vitro release of drug was investigated using ultraviolet (UV) spectroscopy. MTT assay was performed using L929 (NCBI C161) cell line by extraction method on nanofibers with/without drug. The antibacterial activity was performed on nanofibers against Escherichia coli and Staphylococcus aureusbacteria. Nanofibers with concentration ratio of gum tragacanth/gelatin (80 to 20 %) were selected for further investigation. Diameters of nanofiber with/without drug were in the range of 100 and 200 nm, respectively. Also, the results confirmed that there is no possible interaction between drug and nanofiber materials. The drug release profile from nanofibers showed 82% release in 120 h. The result of MTT assay indicated that nanofibers without drug had no toxicity effects. Also cell viability of drug-loaded nanofibers has reached about 91% cell viability after 5 days. Overall, this study confirmed that this nanofiber could potentially be used as a drug carrier for antibacterial agent delivery, specifically against gram-negative bacteria without cytotoxicity effect.

Electrospinning, as a versatile nanofiber fabrication method, has evinced a lot ofattention due to its simplicity, efficiency and ability to produce continuous nanofibers.However, electrospinning of natural polymers such as proteins and polysaccharides seemsto be challenging for different reasons mainly in the absence of appropriate solvent, highviscosity or in some cases polyelectrolyte nature of solutions. Among natural polymers,alginate with its abundant algal source, structural and chemical resemblance to extracellularmatrix and desirable properties like biocompatibility and biodegradability, has attracted theattention of researchers extensively. Alginate has a great potential in many applications indifferent areas in medicine including tissue engineering, drug delivery and wound dressingfabrication. Also a vast number of studies in literature have focused on fabricating alginatenanofibers through electrospinning, no considerable success in achieving nanofibers withhigh alginate content has been reported. Through evaluating different studies and reports inthis regard, it becomes evident that part of the challenge is due to the lack of a comprehensivedescription focused on investigating and analyzing the conducted studies and underlyingstrategies. Hence, the aim of this review is to examine challenges and obstacles in alginateelectrospinning and to open discussions in literature, in order to pave the way for moreintended and successful research in this field.

The high viscosity of pure chitosan solution, limits the production of pure chitosan nanofibers. One approach to overcome this limitation is to mix some other natural biopolymers including proteins with chitosan solution. Visia ervili is a natural protein with low cost and high content of energy. The aim of this study was to produce chitosan visia ervili nanofibers via electrospinning. Firstly, chitosan/visia ervili solutions were prepared in trifluroacetic acid solvent. Secondly, nanofibers were produced at the voltage 20 kV and tip to collector distance of 15 cm. Then the fiber morphology, FTIR, and XRD patterns were investigated. According to the result, nanofibers had diameter average of 100 to 250 nanometers. Crystalline structure was decreased after production of nanofiber. In the next step, mint essential oil was encapsulated within chitosan/ visia ervili nanofibers. Finally, according to the results, the ratio of 20% was selected as the best ratio and the morphology, FTIR, XRD of the nanofibers investigated. Also, the release and storage stability of essential oil were examined. FTIR results confirmed the presence of peppermint essential oil in the prepared nanofibers. The encapsulation efficiency of the peppermint essential oil was 71%. Encapsulation of peppermint essential oil in chitosan-protein nanofibers increased the essential oil shelf life from 4 days to 16 days. According to the findings, hydrophobic bioactives such as mint essential oil could be encapsulated within chitosan/visia ervili electrospun nanofibers.

In this study, the nanofibers containing vanillin are introduced as the aromatic mats for food packaging. The cellulose acetate solutions were prepared at 10, 12, and 14% and the nanofibers were produced by means of the electrospinning method. Evaluation of the scanning electronic microscopic (SEM) images and the nanofibers diameter revealed that the 12% cellulose acetate is the optimized level of biopolymer concentration in the process. In the next step, 1% w/w vanillin was incorporated into the nanofibers and the aromatic acetate cellulose electrospuns were produced. The Fourier transform infrared spectroscopy (FTIR), and the vanillin leaching measurements were performed on the aromatic vanillin electrospuns. The results revealed that the vanillin has been entrapted into the nanofibers and its encapsulation efficiency was 85%. Moreover, the influence of the nanofiber diameter on the vanillin release kinetic using the pseudo- second order showed that increasing the nanofiber diameter dramatically decreases the vanillin release.