Preparation and properties of silver‐containing nylon 6 nanofibers formed by electrospinning

Nylon 6 nanofibers containing silver nanoparticles (nylon 6/silver) were successfully prepared by electrospinning. The structure and properties of the electrospun fibers were studied with the aid of scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectroscopy, and X‐ray diffraction. The structural analysis indicated that the fibers electrospun at maximum conditions were straight and that silver nanoparticles were distributed in the fibers. Finally, the antibacterial activities of the nylon 6/silver nanofiber mats were investigated in a broth dilution test against Staphylococcus aureus (Gram‐positive) and Klebsiella pneumoniae (Gram‐negative) bacteria. It was revealed that nylon 6/silver possessed excellent antibacterial properties and an inhibitory effect on the growth of S. aureus and K. pneumoniae. On the contrary, nylon 6 fibers without silver nanoparticles did not show any such antibacterial activity. Therefore, electrospun nylon 6/silver nanocomposites could be used in water filters, wound dressings, or antiadhesion membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Functionally modified,melt‐electrospun thermoplastic polyurethane mats for wound‐dressing applications

The electrospinning of a polymer melt is an interesting process for medical applications because it eliminates the cytotoxic effects of solvents in the electrospinning solution. Wound dressings made from thermoplastic polyurethane (TPU), particularly as a porous structured electrospun membrane, are currently the focus of scientific and commercial interest. In this study, we developed a functionalized fibrillar structure as a novel antibacterial wound‐dressing material with the melt‐electrospinning of TPU. The surface of the fibers was modified with poly(ethylene glycol) (PEG) and silver nanoparticles (nAg's) to improve their wettability and antimicrobial properties. TPU was processed into a porous, fibrous network of beadless fibers in the micrometer range (4.89 ± 0.94 μm). The X‐ray photoelectron spectroscopy results and scanning electron microscopy images confirmed the successful incorporation of nAg's onto the surface of the fiber structure. An antibacterial test indicated that the PEG‐modified nAg‐loaded TPU melt‐electrospun structure had excellent antibacterial effects against both a Gram‐positive Staphylococcus aureus strain and Gram‐negative Escherichia coli compared to unmodified and PEG‐modified TPU fiber mats. Moreover, modification with nAg's and PEG increased the water‐absorption ability in comparison to unmodified TPU. The cell viability and proliferation on the unmodified and modified TPU fiber mats were investigated with a mouse fibroblast cell line (L929). The results demonstrate that the PEG‐modified nAg‐loaded TPU mats had no cytotoxic effect on the fibroblast cells. Therefore, the melt‐electrospun TPU fiber mats modified with PEG and nAg have the potential to be used as antibacterial, humidity‐managing wound dressings. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40132.     

An antibacterial submicron fiber mat with in situ synthesized silver nanoparticles

This work presents an alternative approach for fabricating electrospun submicron highly hydrophilic fiber mats loaded with silver nanoparticles. These fiber mats show a high efficient antibacterial behavior, very attractive for applications like wound healing and skin regeneration processes. The fabrication method is divided in two steps. First, poly(acrylic acid) (PAA) and β‐cyclodextrin (β‐CD) submicron fibers were electrospun and further stabilized using a thermal treatment, yielding stable hydrogel‐like fibers with diameters ranging from 100 nm up to several microns. In the second step, silver ions were loaded into the fibers and then reduced to silver nanoparticles in‐situ. The electrospinning parameters were adjusted to achieve the desired properties of the fiber mat (density, size) and afterwards, the characteristics of the silver nanoparticles (amount, size, aggregation) were tuned by controlling the silver ion loading mechanism. Highly biocide surfaces were achieved showing more than 99.99% of killing efficiency. The two‐step process improves the reproducibility and tunability of the fiber mats. To our knowledge, this is the first time that stable hydrogel fibers with a highly biocide behavior have been fabricated using electrospinning. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Microwave‐assisted rapid fabrication of antibacterial polyacrylonitrile microfibers/nanofibers via nitrile click chemistry and electrospinning

Postmodified polyacrylonitrile (PAN) microfibers/nanofibers with durable antibacterial performance was fabricated by a rapid and green method of microwave irradiation and electrospinning technologies. The fibers were endowed with antibacterial activity because of silver ions, which were embedded into PAN by nitrile click chemistry with microwave irradiation; they were then electrospun into neat and smooth microfibers/nanofibers. The obtained microfibers/nanofibers were tested against Staphylococcus aureus and exhibited powerful and long‐lasting antibacterial properties. The production of endurable antibacterial materials could effectively prevent the spread of microbes and beautify the living environment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45490.     

Antibacterial polycaprolactone electrospun fiber mats prepared by soluble eggshell membrane protein–assisted adsorption of silver nanoparticles

Antibacterial polycaprolactone (PCL) electrospun fiber mats were prepared by coelectrospinning PCL with soluble eggshell membrane protein (SEP) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP), followed by adsorption of silver nanoparticles (Ag NPs) through hydrogen‐bonding interaction between the amide groups of SEP and the carboxylic acid groups capped on the surfaces of Ag NPs. The PCL/SEP fiber mat was characterized by X‐ray photoelectron spectroscopy, indicating the presence of some SEP on the fiber surface. The adsorption of Ag NPs was confirmed by transmission electron microscopy and quantitatively characterized by thermogravimetric analysis. The pH value of the silver sol used for adsorption is very important in view of the amount and dispersion state of Ag NPs adsorbed on the fibers. The Ag NP–decorated PCL/SEP fiber mats prepared at pH 3–5 exhibit strong antibacterial activity against both gram‐negative Escherichia coli and gram‐positive Bacillus subtilis. Antibacterial PCL fiber mats were also obtained similarly with the assistance of collagen (another protein) instead of SEP, showing that protein‐assisted adsorption of Ag NPs is a versatile method to prepare antibacterial electrospun fiber mats. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43850.     

Fabrication of SiO2-ZrO2 composite fiber mats via electrospinning

(1 − x)SiO₂-(x)ZrO₂ (x = 0.1, 0.2) composite fiber mats were prepared by electrospinning their sol-gel precursors of zirconium acetate and tetraethyl orthosilicate (TEOS) without using a polymer binder. The electrospun composite fibers were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and mercury porosimetry. The composite fibers having a tetragonal crystalline ZrO₂ were obtained by calcining the electrospun composite fibers at high temperatures. The results show that the structure and crystallization of ZrO₂ in the composite fibers can be controlled by sintering temperature, while the porosity and morphology of the fiber mats did not depend on the sintering temperature.     

Electrospinning polymer blend of PLA and PBAT: Electrospinnability–solubility map and effect of polymer solution parameters toward application as antibiotic‐carrier mats

Electrospinning of a biodegradable polymer blend of poly(lactic acid) (PLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) is reported for the first time. Effects of several solution parameters on electrospinning are explored, including types of single and binary solvents, binary solvent mixing ratio, polymer blend concentration, polymer blending ratio, and loading content of tetrabutyl titanate as a compatibilizer. An electrospinnability–solubility map of the PLA/PBAT blend is firstly developed for the facile selection of a suitable binary solvent system, thus simplifying the laborious, time‐consuming, trial‐and‐error process. A particular binary solvent system derived from good and non‐solvent serves as the most suitable medium for the successful preparation of homogeneous bead‐free electrospun PLA/PBAT nanofibers. It is revealed that the compatibilizer acts not only as a diameter size tuner for the PLA/PBAT fibers but also as a mechanical property enhancer for the immiscible PLA/PBAT electrospun mats. Moreover, the antibacterial activity of the drug‐loaded PLA/PBAT fibrous mats suggests their potential application as antibiotic‐carrier mats. Preparation of the composite mats comprising bead‐free fibers with an average size at sub‐micrometer scale is also demonstrated, additionally promoting the possibility of using the PLA/PBAT‐based electrospun mats as a matrix of various additives for a wide range of applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46486.     

Novel core‐sheath antimicrobial nanofibrous mats

The poor mechanical properties of electrospun materials remain one of the major hindrances toward their practical application. In this study, we report the synthesis of core‐sheath nanofibrous mats to enhance the mechanical properties of an antimicrobial polymer nanofiber for application in filter media. This objective was achieved via coaxial electrospinning of poly[styrene‐co‐N‐(N′,N′‐dimethyl‐3‐aminopropyl)maleimide] as the sheath which is an antimicrobial polymer and nylon 6 polymer for the core which is well reported for exceptional mechanical properties. Extensive characterization of these fibers was performed using scanning electron microscopy, scanning transmission electron microscopy, confocal fluorescence microscopy as well as attenuated total reflectance Fourier transform spectroscopy to provide evidence of the core‐sheath morphology. Antimicrobial evaluation was also carried out on the fabricated fibers via the live/dead fluorescence technique. This was done to determine if the poly[styrene‐co‐N‐(N′,N′‐dimethyl‐3‐aminopropyl)maleimide] retained its antimicrobial activity. The fibers were found to be effective against the Gram‐positive Staphylococcus aureus (ATCC25925) and Gram‐negative Pseudomonas aeruginosa (ATCC27853). Subsequent tensile testing and filtration experiments provided evidence that the incorporation of the nylon core improved mechanical properties of the nanofiber mats. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46303.     

Transparent poly(methyl methacrylate‐co‐butyl acrylate) nanofibers

Nanofibers of n‐Butyl Acrylate/Methyl Methacrylate copolymer [P(BA‐co‐MMA)] were produced by electrospinning in this study. P(BA‐co‐MMA) was synthesized by emulsion polymerization. The structural and thermal properties of copolymers and electrospun P(BA‐co‐MMA) nanofibers were analyzed using Fourier transform infrared spectroscopy–Attenuated total reflectance (FTIR–ATR), Nuclear magnetic spectroscopy (NMR), and Differential scanning calorimetry (DSC). FTIR–ATR spectra and NMR spectrum revealed that BA and MMA had effectively participated in polymerization. The morphology of the resulting nanofibers was investigated by scanning electron microscopy, indicating that the diameters of P(BA‐co‐MMA) nanofibers were strongly dependent on the polymer solution dielectric constant, and concentration of solution and flow rate. Homogeneous electrospun P(BA‐co‐MMA) fibers as small as 390 ± 30 nm were successfully produced. The dielectric properties of polymer solution strongly affected the diameter and morphology of electrospun polymer fibers. The bending instability of the electrospinning jet increased with higher dielectric constant. The charges inside the polymer jet tended to repel each other so as to stretch and reduce the diameter of the polymer fibers by the presence of high dielectric environment of the solvent. The extent to which the choice of solvent affects the nanofiber characteristics were well illustrated in the electrospinning of [P(BA‐co‐MMA)] from solvents and mixed solvents. Nanofiber mats showed relatively high hydrophobicity with intrinsic water contact angle up to 120°. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4264–4272, 2013     

Preparation of antibacterial biocompatible polycaprolactone/keratin nanofibrous mats by electrospinning

Keratin-based materials are widely used in biomedical applications due to excellent biocompatibility and biodegradability. In this study, keratin was extracted from waste wool fibers and blended with polycaprolactone (PCL) to produce PCL/keratin nanofibrous mats by electrospinning. The electrospun PCL/keratin nanofibrous mats were chlorinated in diluted sodium hypochlorite solution to endow antibacterial properties. The prepared nanofibrous mats were characterized by scanning electron microscopy, X-ray photoelectron, and Fourier infrared spectroscopy. The effect of the chlorination time on the active chlorine loading of the mats was investigated. The chlorinated PCL/keratin nanofibrous mats with 0.78 ± 0.009 wt% active chlorine displayed potent antibacterial activity against Gram-positive Staphylococcus aureus (ATCC 6538) and Gram-negative Escherichia coli O157:H7 (ATCC 43895) with 6.88 and 6.81 log reductions, respectively. It was found that the mats were compatible with mouse fibroblast cells (L929). The chlorinated PCL/keratin nanofibrous mats might find promising applications in the biomedical field.     

Electrospun biocompatible poly (ε-caprolactonediol)-based polyurethane core/shell nanofibrous scaffold for controlled release of temozolomide

The electrospun biocompatible poly (ε-caprolactonediol)-based polyurethane (PCL-Diol-b-PU) core/shell nanofibrous scaffolds were prepared via the coaxial electrospinning process. Temozolomide (TMZ) as an anticancer drug was loaded into the core of fibers to control the release of TMZ for the treatment of glioblastoma. The properties of nanofibers were characterized using XRD, FTIR, SEM, and TEM analysis. The sustained delivery of TMZ without initial burst release was achieved from all prepared core–shell nanofibrous samples over 30 days. The cytotoxicity results revealed that the TMZ-loaded PCL-Diol-b-PU core–shell nanofibers could be used as a drug delivery implant to deliver TMZ against glioblastoma tumors.     

Fabrication of SiO2-ZrO2 composite fiber mats via electrospinning

(1 ? x)SiO₂-(x)ZrO₂ (x = 0.1, 0.2) composite fiber mats were prepared by electrospinning their sol-gel precursors of zirconium acetate and tetraethyl orthosilicate (TEOS) without using a polymer binder. The electrospun composite fibers were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and mercury porosimetry. The composite fibers having a tetragonal crystalline ZrO₂ were obtained by calcining the electrospun composite fibers at high temperatures. The results show that the structure and crystallization of ZrO₂ in the composite fibers can be controlled by sintering temperature, while the porosity and morphology of the fiber mats did not depend on the sintering temperature.     

Controlled release of doxycycline within core/shell poly(ε-caprolactone)/poly(ethylene oxide) fibers via coaxial electrospinning

The development of fibers with desired drug release properties has gained a high research interest for water-soluble drugs with controlled drug delivery systems obtained by coaxial electrospinning technique. The objective of this study is to achieve the controlled-release of doxycycline hyclate (DOXH) from the fabricated electrospun fibers. In this case, three different electrospun core/shell fibers have been successfully fabricated using this technique and the model drug, DOXH, has been entrapped in the core layers. The results of the structural properties and in vitro release studies have been compared with electrospun monostructural fibers fabricated by conventional electrospinning technique. Scanning electron microscopy and transmission electron microscopy images have proved that the fabricated electrospun fibers have core/shell structures. Fourier transform infrared spectroscopy has shown convenient interaction and compatibility between polymers and the model drug. X-ray diffraction analysis has revealed that all the encapsulated DOXH are transferred into amorphous physical state and lost its crystalline state in the fibers. Moreover, drug release studies have demonstrated that the electrospun core/shell fibers show a better-controlled release than the monostructural fibers. It can be concluded that the fibers obtained by blending hydrophilic and hydrophobic polymers such as poly(ε-caprolactone) and poly(ethylene oxide) in both shell and core sides are promising candidate for controlled drug release.     

Electrospun antibacterial nylon nanofibers through in situ synthesis of nanosilver: preparation and characteristics

A new method for production of nylon nanofibers with antibacterial properties containing silver nanoparticles (nylon nanofibers/Ag NPs) is introduced via in situ synthesis of nano-silver by reduction of silver nitrate in the polymer solution prior to electrospinning. The properties of the electrospinning solutions and the structures of the electrospun fibers were studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), UV?Cvis spectrophotometer and reflection spectrophotometer. Further, the antibacterial properties of the nanofibers were investigated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. Interestingly, an antibacterial properties has been found on nylon 6 nanofibers while the nylon nanofibers/Ag NPs showed excellent antibacterial activities against both tested bacteria. The produced nylon nanofibers/Ag NPs can be a good candidate for biomedical applications, water and air filtration.     

Effect of fiber structure on the properties of the electrospun hybrid membranes composed of poly(ε‐caprolactone) and gelatin

To elucidate the effect of fiber structure on the properties of the electrospun gelatin/PCL hybrid membranes, three types of fibers with different structures, i.e., core‐shell, blend, and mixed fibers were fabricated. The crystallinity, wettability, swelling degree, and mechanical properties of the hybrid membranes were compared. It was found that the crystalline characteristics of PCL in the core‐shell fibers were different from the fibers fabricated by the other two methods. That is, the orientation degree of the PCL chains in the core‐shell fibers was higher than that in both blend and mixed fibers. The wettability of the hybrid membrane was dependent on both the composition and structure of the electrospun fibers. Blended fibers exhibited the highest hydrophobicity because of the enrichment of PCL at the fiber surface. Contrarily, the mixed fibers possessed the highest mechanical strength of 3–5.18 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure and properties of electrospun poly(vinylidene fluoride)/polycarbonate membranes after hot‐press

Poly(vinylidene fluoride) (PVDF)/polycarbonate (PC) dispersed solutions were electrospun into ultrafine core/shell fibers and modified by hot‐press. Morphology, tensile properties, porosity, and liquid absorption of the electrospun membranes as well as the crystallinity of PVDF were examined before and after hot‐press. Results showed that the tensile strength and tensile modulus of the electrospun membranes increased after hot‐press, especially when poly(methyl methacrylate) (PMMA) or benzyl triethylammonium chloride (BTEAC) was introduced for the formation of distinct core/shell fiber structure. The elongation of the hot‐pressed electrospun PVDF/PC membrane with addition of BTEAC was also significantly enhanced by reason of the clearest core/shell structure. The crystallinity of PVDF did not change too much before and after hot‐press, however the porosity and liquid absorption of the hot‐pressed electrospun membranes decreased to about 58% and around 75–90%, respectively, with no significant differences between PVDF/PC, PVDF/PC/PMMA, and PVDF/PC with BTEAC membranes. This study could be an example of electrospun membranes in multi‐polymer components and it could be extended to other systems of electrospinning for applications in filtration and so on. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Drug release from electrospun fibers of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) grafted with poly(N‐vinylpyrrolidone)

Poly(N‐vinylpyrrolidone) (PVP) groups were grafted onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) backbone to modify the properties of PHBV and synthesize a new novel biocompatible graft copolymer. Based on these graft copolymers, electrospun fiber mats and commonly cast films were explored as drug delivery vehicles using tetracycline hydrochloride as a model drug. Toward that end, the fibers were electrospun and the films were cast from chloroform solutions containing a small amount of methanol to solubilize the drug. The Brookfield viscosities of the solution were determined to achieve the optimal electrospinning conditions. The vitro release of the tetracycline hydrochloride from these new drug delivery systems was followed by UV–vis spectroscopy. To probe into the factors affected on the release behavior of these drug delivery systems, their water absorbing abilities in phosphate buffer solution were investigated, together with their surface hydrophilicity, porosity and crystallization properties were characterized by water contact angles, capillary flow porometer, DSC, and WAXD, respectively. The morphological changes of these drug delivery vehicles before and after release were also observed with SEM. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Improvement of carbon nanotube dispersion in electrospun polyacrylonitrile fiber through plasma surface modification

In this study, surfaces of multiwalled carbon nanotubes (CNTs) were functionalized with poly(hexafluorobutyl acrylate) (PHFBA) thin film using a rotating-bed plasma-enhanced chemical vapor deposition (PECVD) method without imparting any defects on their surfaces. Polyacrylonitrile (PAN) electrospun polymer fiber mats and composite fiber mats with CNTs and functionalized CNTs (f-CNTs) were prepared. The wettability and chemical and morphological properties of the synthesized fiber mats were investigated, and the dispersion of CNTs and f-CNTs in the polymer matrix was compared according to the contact angle results of electrospun polymer mats. According to the chemical and morphological characterization results, PHFBA-coated CNTs were dispersed more uniformly in the polymer matrix than the uncoated CNTs. The f-CNTs/PAN composite fiber mat exhibits a lower surface energy than the pristine CNTs/PAN fiber mat. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47768.     

Poly(hydroxybutyrate‐co‐hydroxyvalerate) and bovine serum albumin blend prepared by electrospinning

Electrospinning is a method for the preparation of nanosized polymer fibers. Here, electrospinning is used to prepare a blend of a polyester, poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV), and a globular protein, bovine serum albumin (BSA). The electrospun blend film is compared with a solution‐cast blend film and with single‐component electrospun films made of PHBV and BSA. In the electrospun blend films, BSA manifests itself as flat ribbons and a fine network formed from fibers less than 50 nm in diameter. The dissolution rate of BSA from the electrospun blended film is lower than from the solution‐cast one. The films are characterized using scanning electron microscopy, differential scanning calorimetry, and contact‐angle measurements. The obtained PHBV+BSA blend films have several emergent properties: a slow BSA dissolution rate, a fine BSA network, and unusual thermal behavior. Thus, the PHBV+BSA blend films introduce a new class of polymer–protein blends. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45090.     

Characteristics and cadmium extraction performance of PVC/Aliquat 336 electrospun fibres in comparison with polymer inclusion membranes

Electrospun fibres and polymer inclusion membranes (PIMs) were prepared from polyvinyl chloride (PVC) and Aliquat 336. Morphological and thermomechanical properties of the electrospun mats differed notably from those of PIMs. The plasticizing effect of Aliquat 336 on electrospun PVC/Aliquat 336 fibres was confirmed by the shifting of the glass transition temperature (T_g). By contrast, Aliquat 336 did not act as a plasticizer in PIMs as T_g was independent of Aliquat 336 concentration. Cadmium extraction to electrospun fibres could occur at a lower Aliquat 336 content (i.e. 6 wt.%) compared with PIMs. At 40 wt.% Aliquat 336 content, both PIMs and electrospun fibrous mats exhibited similar extraction rate.