Fabrication of antibacterial silver nanoparticle‐modified chitosan fibers using Eucalyptus extract as a reducing agent

Green chemical method could be a promising route to achieve large scale synthesis of nanostructures for biomedical applications. Here, we describe a green chemical synthesis of silver nanoparticles (Ag NPs) on chitosan‐based electrospun nanofibers using Eucalyptus leaf extract. A series of silver salt (AgNO₃) amounts were added to a certain composition of chitosan/polyethylene oxide aqueous acetic acid solution. The solutions were then electrospun to obtain nanofibrous mats and then, morphology and size of nanofibers were analyzed by scanning electron microscopy (SEM). Incubation of AgNO₃‐containing mats into Eucalyptus leaf extract led to the formation of Ag NP clusters with average diameter of 91 ± 24 nm, depicted by SEM and transmission electron microscopy. Surface enhanced Raman spectroscopy also confirmed formation of Ag NPs on the nanofibers. The mats also showed antimicrobial activity against Escherichia coli and Staphylococcus aureus bacteria with bigger inhibition zone for extract‐exposed mats against S. aureus. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42133.     

Studies on the synthesis of electrospun PAN‐Ag composite nanofibers for antibacterial application

We have successfully synthesized polyacrylonitrile (PAN) nanofibers impregnated with Ag nanoparticles by electrospinning method at room temperature. Briefly, the PAN‐Ag composite nanofibers were prepared by electrospinning PAN (10% w/v) in dimethyl formamide (DMF) solvent containing silver nitrate (AgNO₃) in the amounts of 8% by weight of PAN. The silver ions were reduced into silver particles in three different methods i.e., by refluxing the solution before electrospinning, treating with sodium borohydride (NaBH₄), as reducing agent, and heating the prepared composite nanofibers at 160°C. The prepared PAN nanofibers functionalized with Ag nanoparticles were characterized by field emission scanning electron microscopy (FESEM), SEM elemental detection X‐ray analysis (SEM‐EDAX), transmission electron microscopy (TEM), and ultraviolet‐visible spectroscopy (UV‐VIS) analytical techniques. UV‐VIS spectra analysis showed distinct absorption band at 410 nm, suggesting the formation of Ag nanoparticles. TEM micrographs confirmed homogeneous dispersion of Ag nanoparticles on the surface of PAN nanofibers, and particle diameter was found to be 5–15 nm. It was found that all the three electrospun PAN‐Ag composite nanofibers showed strong antibacterial activity toward both gram positive and gram negative bacteria. However, the antibacterial activity of PAN‐Ag composite nanofibers membrane prepared by refluxed method was most prominent against S. aureus bacteria. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and characterization of poly(vinyl alcohol) cryogel‐silver nanocomposites and evaluation of blood compatibility,cytotoxicity, and antimicrobial behaviors

In this investigation, cryogels composed of poly(vinyl alcohol) (PVA) were prepared by repeated freeze‐thaw method. The prepared cryogels served as templates for producing highly stable and uniformly distributed silver nanoparticles via in situ reduction of silver nitrate (AgNO₃) using alkaline formaldehyde solution as reducing agent. The structure of the PVA/Ag cryogel nanocomposites was characterized by a Fourier transform infrared and Raman spectroscopy. The morphologies of pure PVA cryogels and PVA/Ag nanocomposites were observed by a scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The SEM analysis suggested that cryogels show a well defined porous morphology whereas TEM micrographs revealed the presence of nearly spherical and well separated Ag nanoparticles with diameter about 100 nm. XRD results showed all relevant Bragg's reflections for crystal structure of silver nanoparticles. The amount of silver in cryogel nanocomposites and thermal stability were determined by inductively coupled plasma atomic emission spectrometry (ICP‐AES) and thermogravimetric analysis measurements. Mechanical properties of nanocomposites were observed in terms of tensile strength. The antibacterial studies of the synthesized nanosilver containing cryogels showed good antibacterial activity against both gram‐negative and gram‐positive bacteria. The prepared PVA/Ag nanocomposites were also investigated for swelling and deswelling behaviors. The results reveal that both the swelling and deswelling process depends on the chemical composition of the cryogel silver nanocomposites, number of freeze‐Thaw cycles and pH and temperature of the swelling medium. The biocompatibility of the prepared nanocomposites was judged by in vitro methods of percent hemolysis and protein (BSA) adsorption. POLYM. COMPOS., 36:1983–1997, 2015. © 2014 Society of Plastics Engineer     

Antibacterial properties of raw and degummed silk with nanosilver in various conditions

This article is concerned with the effects of nanosized silver colloids on the antibacterial properties of silk fibers against two kinds of bacteria: Staphylococcus aureus and Escherichia coli. Different concentrations of silver nanoparticles (Ag NPs; 10, 25, 50, and 100 ppm) were applied to silk fibers by an exhaust method. The effect of medium pH on the Ag NP uptake on the fibers was studied. Also, sodium carbonate and sodium chloride were added to the liquor as auxiliaries. Scanning electron microscopy was used to observe the morphology of the silk fibers. The antibacterial activity was examined by a bacterial counting method. Energy‐dispersive X‐ray spectroscopy was also used to show the elements on the surface of the silk fibers. We observed that the antibacterial activity increased with silver treatment. It also increased with decreasing pH, especially for the raw silk. The use of NaCl improved the uniformity of the Ag NPs on the fiber surface and increased the antibacterial activities. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of antibacterial,biocompatible core–shell fibers produced by coaxial electrospinning

Coaxial electrospinning is a method for producing fibrous mats with optional features, such as antibacterial properties, controllable release, and hydrophobicity based on shell materials. Because these features are important in biomedical applications, in this study, biocompatible hydrophobic polymer (polycaprolactone) and hydrophilic polymer [poly(vinyl alcohol)] with silver nanoparticles loaded in the core solution were coaxially electrospun. The effect of silver addition on the conductivity and viscosity of the solutions, chemical structure of the fiber mats, mechanical properties, porosity, hydrophobicity, water vapor transmission rate (WVTR), silver release, and antibacterial properties were investigated. Fibers with silver exhibited less porosity and a lower WVTR and a greater contact angle than the fibers without silver. Furthermore, the core–shell fibers reduced the burst release of silver and successfully prevented the growth of Escherichia coli and Staphylococcus aureus bacteria. Therefore, it seems that these fibers are suitable for providing electrospun mats with long‐term antibacterial properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44979.     

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     

Preparation and characterization of electrospun poly(ε‐caprolactone)/poly(vinyl pyrrolidone) nanofiber composites containing silver particles

A nanofiber membrane composed of poly(ε‐caprolactone) (PCL), poly(vinyl pyrrolidone) (PVP), and silver nanoparticles was prepared via electrospinning technique. The morphology and structure of the PCL/PVP/Ag nanofibers composite were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). The SEM images showed that various composites of PCL/PVP/Ag could be electrospun to yield continuous and uniform nanofibers. FTIR spectra indicated that the molecular interactions between PCL and PVP are weak. The hydrophilicity, mechanical property, and swelling behavior of the as‐spun composites can be manipulated by altering the blend ratio of PCL/PVP. XRD patterns and XPS spectra showed that the Ag nanoparticles were dispersed in the PCL/PVP nanofiber composites; and the Ag nanoparticles endowed the PCL/PVP/Ag composite with antibacterial activities. The obtained PCL/PVP/Ag nanofiber composites with the morphology similar to that of native extracellular matrix have the potential to create a moist environment and to kill bacteria, which make it possible to be used for wound dressing application. POLYM. COMPOS., 37:2847–2854, 2016. © 2015 Society of Plastics Engineers     

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.     

Self synthesize of silver nanoparticles in/on polyurethane nanofibers: Nano‐biotechnological approach

In this study, we are introducing a new class of Polyurethane (PU) nanofibers containing silver nanoparticles (NPs) by electrospinning. A simple method not depending on the addition of foreign chemicals has been used to self‐synthesize of silver NPs in/on PU nanofibers. Typically, a sol?gel consisting of AgNO₃/PU/N,N‐dimethylformamide (DMF) has been electrospun and aged for a week, so silver NPs have been created in/on PU nanofibers. Syntheses of silver NPs were carried out by exploiting the reduction ability of the DMF solvent which is the main constituent to obtain PU electrospun nanofibers in decomposition of silver nitrate precursor into silver NPs. Physiochemical characterizations confirmed well oriented nanofibers and good dispersing of pure silver NPs. Various parameters affecting utilizing of the prepared nanofibers on various nano‐biotechnological fields have been studied. For instance, the obtained nanofiber mats were checked for mechanical properties which showed the improvement of the tensile strength upon increase in silver NPs content. Moreover, the nanofibers were subjected to 10 times successive washing experiments with using solid to liquid ratio of 3 : 5000 for 25 h, UV spectroscopy analysis reveals no losses of silver NPs from the PU nanofibers. 3T3‐L1 fibroblasts were cultured in presence of the designed nanofibers. The morphological features of the cells attached on nanofibers were examined by BIO‐SEM, which showed well attachment of cells to fibrous mats. The cytotoxicity results indicated absence of toxic effect on the 3T3‐L1 cells after cell culturing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Morphological,thermal, and mechanical properties of poly(ε‐caprolactone)/poly(ε‐caprolactone)‐grafted‐cellulose nanocrystals mats produced by electrospinning

Electrospun nanocomposites of poly(ε‐caprolactone) (PCL) incorporated with PCL‐grafted cellulose nanocrystals (PCL‐g‐CNC) were produced. PCL chains were grafted from cellulose nanocrystals (CNC) surface by ring‐opening polymerization. Grafting was confirmed by infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA). The resulting PCL‐g‐CNC were then incorporated into a PCL matrix at various loadings. Homogeneous nanofibers with average diameter decreasing with the addition of PCL‐g‐CNC were observed by scanning electron microscopy (SEM). PCL‐g‐CNC domains incorporated into the PCL matrix were visualized by transmission electron microscopy (TEM). Thermal and mechanical properties of the mats were analyzed by differential scanning calorimetry (DSC), TGA and dynamic mechanical analysis (DMA). The addition of PCL‐g‐CNC into the PCL matrix caused changes in the thermal behavior and crystallinity of the electrospun fibers. Significant improvements in Young's modulus and in strain at break with increasing PCL‐g‐CNC loadings were found. These results highlighted the great potential of cellulose nanocrystals as a reinforcement phase in electrospun PCL mats, which can be used as biomedical materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43445.     

Study of antibacterial properties of polypropylene filled with surfactant‐coated silver nanoparticles

Medical applications require, in most cases, antibacterial protection. The use of silver (Ag) gives important antibacterial properties since silver is highly toxic for bacteria. In this research work, we have used silver nanoparticles (Ag NPs) with different surfactants, polyvinyl pyrrolidone (PVP) and oleic acid (OA) to facilitate dispersion. PP‐Ag NPs compounds were prepared by melt mixing, and the effects of the processing conditions on nanoparticles' dispersion were investigated by transmission electron microscopy (TEM). The antibacterial efficiency of PP‐Ag NPs compounds against Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 8379 was evaluated. Results show that good dispersion is obtained with rotating speeds in the 350–500 rpm range. TEM analysis reveals balanced dispersion and presence of some Ag NPs aggregates. Regarding antimicrobial properties, the use of PVP as surfactant leads to “significant” antimicrobial activity of 1.5 against Staphylococcus aureus and Escherichia coli; on other hand, the use of oleic acid (OA) as surfactant leads to strong protection against Staphylococcus aureus (antimicrobial activity between 2.5 and 3.3) but the overall protection against Escherichia coli is very low (lower than 1). Results show that the use of surfactants for Ag NPs has important effects on antibacterial properties of polypropylene filled with coated Ag NPs. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Fabrication and characterization of silver nanoparticle-incorporated bilayer electrospun–melt-blown micro/nanofibrous membrane

In this study, we fabricated an antifouling bilayered fibrous filter media having micro-nonwoven by melt blowing and nano-nonwoven by electrospinning process. Silver nanoparticle-incorporated polyurethane nanofibers were electrospun on the meltblown fiber of polypropylene. Silver nanoparticles were synthesized in situ in the polyurethane electrospun nanofibers through reduction of silver nitrate. The filter media were characterized by field emission scanning electron microscope, transmission electron microscopy, and X-ray diffraction and energy-dispersive X-ray spectroscopy analyses. The composite membrane showed that a thin layer of electrospun nanofibers improved the filtration efficiency without substantial increase in pressure drop. In situ synthesis of Ag NPs imparted the antibacterial and antifouling characteristics to the membrane.     

Antibacterial activities of novel nanocomposite biofilms of chitosan/phosphoramide/Ag NPs

Novel nanocomposite films of chitosan/phosphoramide/Ag NPs were prepared containing 1–5% of silver nanoparticles. The Ag NPs were synthesized according to the citrate reduction method. The XRD and SEM analysis of Ag NPs, chitosan (CS), phosphoramide (Ph), CS/Ph, CS/Ag NPs films and the nanocomposite films 1–5 containing CS/Ph/1–5% Ag NPs were investigated. The in vitro antibacterial activities were evaluated against four bacteria including two Gram‐positive Staphylococcus aureus (S. aureus), Bacillus cereus (B. cereus) and two Gram‐negative Escherchia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) bacteria. Results revealed greater antibacterial effects of the films against Gram‐positive bacteria. Also, nanocomposite films containing higher percent of Ag NPs showed more antibacterial activities. POLYM. COMPOS. 36:454–466, 2015. © 2014 Society of Plastics Engineers     

Ultrasmall Ag nanocrystals supported on chitosan/PVA nanofiber mats with bifunctional properties

Bifunctional nanofiber mats consisting of chitosan (CS), poly(vinyl alcohol) (PVA), and silver nanocrystals (Ag NCs) have been fabricated by a facile electrospinning method. The formation and presence of Ag NCs supported on CS/PVA nanofibers are confirmed by ultraviolet‐visible spectroscopy and X‐ray diffraction. The morphology of the samples is characterized by transmission electron microscopy and scanning electron microscopy. The prepared Ag NCs/CS/PVA nanofiber mats show pronounced antibacterial activity against Escherichia coli and excellent filtration property for suspended particulate matter (SPM) particles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46504.     

Electrospun polyurethane membrane with Ag/ZnO microparticles as an antibacterial surface on polyurethane sheets

A method of antibacterial modification of the polyurethane (PU) surface is presented in this article. An electrospun PU membrane with an incorporated antibacterial agent was applied as a coating of the PU sheets. As an antibacterial agent, a hybrid bimetallic filler was used; it combined the antibacterial effects of silver and zinc oxide. With an electrospun submicrometer‐fiber membrane, the filler was uniformly and thinly applied on the PU surface by compression molding. The antibacterial activities of three filler concentrations were tested, and they demonstrated an effective antibacterial action against Staphylococcus aureus and Escherichia coli. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43020.     

Fabrication of patterned PDLLA/PCL composite scaffold by electrospinning

Fabricating fibrous electrospun scaffolds with controllable fiber‐arrangement have gained an increasing attention in the field of tissue engineering. In this study, the composite patterned D,L ‐poly(lactic acid)/poly(ε‐caprolactone) (PDLLA/PCL) scaffolds were fabricated via electrospinning for the first time, and the order degree and contractibility of patterned composite scaffolds with different PDLLA/PCL ratios were further investigated. The results showed that the order degree of the pattern and in vitro shrinkage behaviors of PDLLA/PCL electrospun mats could be finely tuned by controlling blending ratios. The PDLLA/PCL electrospun mats with the ratio 50/50 showed the most balanced properties with controllable pattern structure and appropriate dimensional stability, and they might be a suitable candidate for tissue engineering application. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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.     

Surface modification of electrospun chitosan nanofibrous mats for antibacterial activity

Chitosan (CS) blended with poly(ethylene oxide) (PEO) was electrospun into nanofibrous mats. The spinning solution of 6.7 : 0.3 (% w/v) of CS : PEO was dissolved in a 70 : 30 (v/v) trifluoroacetic acid/dichloromethane solution. The obtained fibers were smooth without beads on their surfaces and average diameter of the fiber was 272 ± 56 nm. N‐(2‐hydroxyl) propyl‐3‐trimethyl ammonium chitosan chloride (HTACC) and N‐benzyl‐N,N‐dimethyl chitosan iodide (QBzCS) were each prepared from the CS/PEO mats. They were identified by Fourier‐transform infrared and X‐ray photoelectron spectroscopy and degree of swelling in water. Both quaternized electrospun chitosan mats exhibited superior antibacterial activity to the unmodified electrospun CS/PEO against Staphylococcus aureus and Escherichia coli at short contact times. After 4 h of contact, the reduction of both bacterial strains by CS/PEO, HTACC, and QBzCS was equal at about 99–100%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40981.