Antimicrobial Nanofibers Research Articles

Core-Shell Structured Antimicrobial Nanofiber Dressings Containing Herbal Extract and Antibiotics Combination for the Prevention of Biofilms and Promotion of Cutaneous Wound Healing.

Burn wounds are susceptible to microbial invasion from both resident and exogenous bacteria, which becomes a critical public health issue and causes substantial economic burden. There is a perceived demand to produce new antimicrobial wound dressings that hinder bacterial colonization while accelerating the healing process and hence would provide an improved standard of care for patients. Since ancient times, herbal extracts from medicinally important plants have extensively been used for treating burn injuries. This work reports the utility of electrospun nanofibers containing plant extracts and antibiotics combination as a multifunctional scaffold for treating second-degree burns. First, we determined the various components of plant extracts from Gymnema sylvestre by two different processing methods and their synergism with minocycline antibiotics. Then, we prepared core-shell nanofibrous dressings with poly-ε-caprolactone/gelatin laden with minocycline hydrochloride as a shell and gelatin infused with G. sylvestre extracts (ultrasound-assisted extracts and cold macerated extracts) as the core using coaxial electrospinning. The electrospun nanofibers displayed a smooth, continuous, and bead-free morphology with adequate wettability. The presence of extract components in the core-shell nanofibers resulted in enhanced mechanical properties when compared to pristine mats. The core-shell structures resulted in sustained release of the bioactive components when compared to nanofiber blends. Core-shell nanofiber mats containing plant extracts and antibiotic combinations displayed potent antimicrobial and antibiofilm properties while promoting the spread and proliferation of skin cells when compared to pristine mats. In a porcine model of cutaneous second-degree burns, we showed that wounds treated with the antimicrobial dressing improved re-epithelialization and collagen organization in comparison to untreated wounds.

Encapsulation of Lemongrass Oil for Antimicrobial and Biodegradable Food Packaging Applications

Antimicrobial gelatin nanofibers with lemongrass essential oil (Gt/LEO) were successfully fabricated by elec-trospinning as potential biodegradable and active food packaging. Following the determination of the key components and the composition of the LEO by a Gas chromatography-mass spectrometry (GC-MS) headspace analysis, the antimicrobial activity of LEO was tested against four different bacteria. Gt/LEO solutions were prepared and characterized before the electrospinning process. All the prepared solutions could be electro-spun, and the effect of LEO on electrospinnability was investigated by measuring conductivity, surface tension, and dielectric constant. The average diameter of pure gelatin nanofibers was 110 ± 39 nm and increased with the rise in essential oil content, similar to other studies. The structure of all nanofibers was smooth, stable, homogenous, and bead-free. The maximum growth inhibition rate (GIR) of Gt/10% LEO nanofilms was 99.09% against Staphylococcus aureus and 96.63% for Salmonella Typhimurium. Nanofilms incorporated with and without LEO displayed similar major Fourier transform infrared (FTIR) spectroscopy peaks showing the effective penetration of LEO in gelatin fibers without chemical interaction or destroying the structure of LEO or gelatin. Thermal analyses indicated that thermal stability of the essential oil enhanced by encapsulation. Overall, this study demonstrates that Gt/LEO nanofibers have a promising prospect in the area of antimicrobial food packaging.

Antimicrobial Nanofiber Based Filters for High Filtration Efficiency Respirators.

Electrospinning has been used to develop and upscale polyacrylonitrile (PAN) nanofibers as effective aerosol filtration materials for their potential use in respirators. The fibers were deposited onto non-woven spunbond polypropylene (SPP) and the basis weight (grammage, g/m2) was varied to assess the resulting effect on filtration efficiency and breathing resistance of the materials. The results indicated that a basis weight in excess of 0.4 g/m2 of PAN electrospun fibers yielded a filtration efficiency over 97%, with breathing resistance values that increased proportionally with the amount of basis weight added. With the aim of retaining filter efficiency whilst lowering breathing resistance, the basis weight of 0.4 g/m2 and 0.8 g/m2 of PAN electrospun fibers were strategically split up and stacked with SPP in different configurations. The results suggested that a symmetric structure based on SPP/PAN/PAN/SPP was the optimal structure, as it reduces SPP consumption while maintaining an FFP2-type of filtration efficiency, while reducing breathing resistance, specially at high air flow rates, such as those mimicking FFP2 exhalation conditions. The incorporation of zinc oxide (ZnO) nanoparticles within the electrospun nanofibers in the form of nanocomposites, retained the high filtration characteristics of the unfilled filter, while exhibiting a strong bactericidal capacity, even after short contact times. This study demonstrates the potential of using the symmetric splitting of the PAN nanofibers layer as a somewhat more efficient configuration in the design of filters for respirators.

Sustainable Rabbit Skin Glue to Produce Bioactive Nanofibers for Nonactive Wound Dressings.

This paper assessed the collagen glue (Col) from rabbit skin for use as a raw material in combination with different water-based dispersants of antimicrobial agents such as ZnO NPs, TiO2 NPs doped with nitrogen and Ag NPs (TiO2-N-Ag NPs), and chitosan (CS) for the production of biocompatible and antimicrobial nanofibers. The electrospun nanofibers were investigated by scanning electron microscopy (SEM), attenuated total reflectance in conjunction with Fourier-transform infrared spectroscopy (ATR-FT-IR) analyses and antioxidant activity. The biocompatibility of electrospun nanofibers was investigated on cell lines of mouse fibroblast NCTC (clone L929) using MTT test assays. Antimicrobial activity was performed against Escherichia coli and Staphylococcus aureus bacteria and Candida albicans pathogenic fungus. Electrospun antimicrobial nanofibers based on collagen glue achieved reduction in the number of viable microorganisms against both fungi and bacteria and exhibited multiple inhibitory actions of fungal and bacterial strains. The electrospun nanofibers showed average dimension sizes in the range of 30–160 nm. The results indicated that both Col/TiO2-N-Ag NPs and Col/CS formulations are suitable for cell proliferation and may be useful for producing of nonactive wound dressings.

Fabrication of Antimicrobial Nanofiber Air Filter Using Activated Carbon and Cinnamon Essential Oil

Recently, air quality is seriously worsening because of micro dust. As a result, respiratory and heart disease patients are also increasing every year. Therefore, the development of a highly efficient air filter media is required. In this study, we developed an antibacterial air filter media with activated carbon (AC) and cinnamon essential oil (CO). 12 wt.% polyurethane (PU) solution mixed with CO and AC was electrospun to prepare the AC+CO+PU nanofiber mat. We studied various characteristics of the AC+CO+PU nanofibrous mat. The surface morphology of mats in different concentration ratios was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We confirmed the antimicrobial activity of the nanofibrous mat using zone of inhibition test with Staphylococcus aureus and Escherichia coli. Air filter test was carried out to observe air filtration efficiency and pressure drop. This data was used to calculate the quality factor of the fabricated nanofiber air filter media. The fabricated antimicrobial nanofiber air filter media can be applied to various fields such as personal masks, air purification devices and bio applications.

Vancomycin-functionalized Eudragit-based nanofibers: Tunable drug release and wound healing efficacy

There is an unmet demand for local vancomycin (VAN) delivery scaffolds with site retention and tunable release properties for cutaneous and surgical wounds. Nanofibers as drug delivery/cell regeneration promoting scaffolds offer great promise in this respect. High loading of the polar VAN into polymeric structures with tunable release properties can be achieved by simultaneous chemical bonding and polymer blending. Electrospinnable vancomycin-functionalized Eudragit E100 with a relatively high drug content and antibacterial activity (E-VAN) was investigated for the development of antimicrobial nanofibers with modifiable hydrophilicity, degradability, mechanical and release properties by blending with selected Eudragit polymers. A platform of fast dissolving nanofibers of value in immediate release applications and nanofibers with a wide spectrum of biphasic release profiles with either fast or sustained drug release at low, high and physiological pH for at least 7 days was generated. A selected nanofiber formulation with a relatively small size, adequate hydrophilicity, structural stability, and biphasic release profile at pH 7.4 showed high antibacterial activity against Staphylococcus aureus and healing efficacy of Staphylococcus aureus-inoculated full thickness excision wounds in a rat model. The E-VAN-based Eudragit nanofibers developed offer potential as versatile antimicrobial delivery/cell regeneration scaffolds for local applications under diverse pH conditions.

Synthesis and characterization of antimicrobial wound dressing material based on silver nanoparticles loaded gum Arabic nanofibers

Gum Arabic (GA) is a biocompatible polymer with the necessary requirements for a wound dressing. However, electrospinning of GA is a bottleneck due to its physico-chemical properties. The aim of this study was to fabricate an antimicrobial nanofibers mat from GA with suitable porosity, water absorption, water vapor permeability and mechanical strength. For this purpose, the composition of polycaprolacton (PCL)-coated GA-polyvinyl alcohol (PVA) nanofibers mat was optimized based on the possible highest porosity, water absorption and water vapor permeability, and then silver nanoparticles (AgNPs) loaded nanofibers mat was prepared based on this composition. The synthesis of AgNPs was supported by UV–vis and ICP analyses. The structure of mat and its constituents were characterized by FE-SEM, XRD and FTIR. The results showed that the average diameter of nanofibers was in the range of 150 to 250 nm with the porosity, water absorption and water vapor permeability of 37.34%, 547.30% and 2235.50 g/m2.day, respectively. The antimicrobial activity of mat against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans was proved. Moreover, the cytotoxicity of mat showed the good biocompatibility for the mouse embryonic fibroblast cells. This study introduced PCL-coated GA-PVA-AgNPs as an effective antimicrobial mat alternative for commercial wound dressing.

Nylon-6/chitosan core/shell antimicrobial nanofibers for the prevention of mesh-associated surgical site infection

The state-of-the-art hernia meshes, used in hospitals for hernia repair, are predominantly polymeric textile-based constructs that present high mechanical strength, but lack antimicrobial properties. Consequently, preventing bacterial colonization of implanted prosthetic meshes is of major clinical relevance for patients undergoing hernia repair. In this study, the co-axial electrospinning technique was investigated for the development of a novel mechanically stable structure incorporating dual drug release antimicrobial action. Core/shell structured nanofibers were developed, consisting of Nylon-6 in the core, to provide the appropriate mechanical stability, and Chitosan/Polyethylene oxide in the shell to provide bacteriostatic action. The core/shell structure consisted of a binary antimicrobial system incorporating 5-chloro-8-quinolinol in the chitosan shell, with the sustained release of Poly(hexanide) from the Nylon-6 core of the fibers. Homogeneous nanofibers with a "beads-in-fiber" architecture were observed by TEM, and validated by FTIR and XPS. The composite nanofibrous meshes significantly advance the stress–strain responses in comparison to the counterpart single-polymer electrospun meshes. The antimicrobial effectiveness was evaluated in vitro against two of the most commonly occurring pathogenic bacteria; S. aureus and P. aeruginosa, in surgical site infections. This study illustrates how the tailoring of core/shell nanofibers can be of interest for the development of active antimicrobial surfaces.

Multifunctional Antimicrobial Nanofiber Dressings Containing ε-Polylysine for the Eradication of Bacterial Bioburden and Promotion of Wound Healing in Critically Colonized Wounds.

Bacterial colonization of acute and chronic wounds is often associated with delayed wound healing and prolonged hospitalization. The rise of multi-drug resistant bacteria and the poor biocompatibility of topical antimicrobials warrant safe and effective antimicrobials. Antimicrobial agents that target microbial membranes without interfering with the mammalian cell proliferation and migration hold great promise in the treatment of traumatic wounds. This article reports the utility of superhydrophilic electrospun gelatin nanofiber dressings (NFDs) containing a broad-spectrum antimicrobial polymer, ε-polylysine (εPL), crosslinked by polydopamine (pDA) for treating second-degree burns. In a porcine model of partial thickness burns, NFDs promoted wound closure and reduced hypertrophic scarring compared to untreated burns. Analysis of NFDs in contact with the burns indicated that the dressings trap early colonizers and elicit bactericidal activity, thus creating a sterile wound bed for fibroblasts migration and re-epithelialization. In support of these observations, in porcine models of Pseudomonas aeruginosa and Staphylococcus aureus colonized partial thickness burns, NFDs decreased bacterial bioburden and promoted wound closure and re-epithelialization. NFDs displayed superior clinical outcome than standard-of-care silver dressings. The excellent biocompatibility and antimicrobial efficacy of the newly developed dressings in pre-clinical models demonstrate its potential for clinical use to manage infected wounds without compromising tissue regeneration.

Continuous Fabrication of Antimicrobial Nanofiber Mats Using Post-Electrospinning Functionalization for Roll-to-Roll Scale-Up

The facile fabrication of antimicrobial fiber mats with surface-attached quaternary ammonium compounds (QACs) as the contact-killing antimicrobials was demonstrated. The entire process was designed...

Lipid membrane interactions of self-assembling antimicrobial nanofibers: effect of PEGylation.

Supramolecular assembly and PEGylation (attachment of a polyethylene glycol polymer chain) of peptides can be an effective strategy to develop antimicrobial peptides with increased stability, antimicrobial efficacy and hemocompatibility. However, how the self-assembly properties and PEGylation affect their lipid membrane interaction is still an unanswered question. In this work, we use state-of-the-art small angle X-ray and neutron scattering (SAXS/SANS) together with neutron reflectometry (NR) to study the membrane interaction of a series of multidomain peptides, with and without PEGylation, known to self-assemble into nanofibers. Our approach allows us to study both how the structure of the peptide and the membrane are affected by the peptide–lipid interactions. When comparing self-assembled peptides with monomeric peptides that are not able to undergo assembly due to shorter chain length, we found that the nanofibers interact more strongly with the membrane. They were found to insert into the core of the membrane as well as to absorb as intact fibres on the surface. Based on the presented results, PEGylation of the multidomain peptides leads to a slight net decrease in the membrane interaction, while the distribution of the peptide at the interface is similar to the non-PEGylated peptides. Based on the structural information, we showed that nanofibers were partially disrupted upon interaction with phospholipid membranes. This is in contrast with the considerable physical stability of the peptide in solution, which is desirable for an extended in vivo circulation time.

Development of polyvinyl alcohol/β-cyclodextrin antimicrobial nanofibers for fresh mushroom packaging

Under the optimal conditions, a crosslinked electrospun polyvinyl alcohol/cinnamon essential oil/β-cyclodextrin (CPVA-CEO-β-CD) nanofibrous films for sustained release of antimicrobials were successfully prepared. Cinnamon essential oil (CEO) can be sustainably released due to CPVA-CEO-β-CD nanofibers complex delivery systems. The chemical crosslinking and physical welding achieved simultaneously by glutaraldehyde atomization fumigation, making fibers more suitable for fresh food packaging. Nanofibrous films were characterized in terms of SEM, ATR-FTIR, DSC, water contact angle analysis and antibacterial trials. ATR-FTIR and DSC data indicated that CEO was encapsulated in a β-CD cavity and they coexisted in PVA nanofibers. The water contact angle of the crosslinked PVA nanofibrous films increased with CEO and the values were always below 90°. Crosslinked nanofibers possessed fine properties in vitro antibacterial against Staphylococcus aureus and Escherichia coli. Furthermore, CPVA/β-CD/CEO nanofibrous films delayed decay of mushroom during storage, indicating their potential implementation in active food packaging.

Production of poly (ε-caprolactone) Antimicrobial Nanofibers by Needleless Alternating Current Electrospinning

Abstract The present study is focused on the fabrication of antimicrobial polycaprolactone (PCL) nanofibers using uncommon needleless and collector less alternating current (AC) electrospinning. The PCL polymeric solutions (6 & 12 wt.%) were prepared using 1:1 acetic acid and formic acid. The antimicrobial agent chlorhexidine (CHX) was added to the PCL precursor solution at 1 wt%. The PCL/CHX solutions (6 &12 wt.%) were electrospinnable at the applied AC potential of 25kV and 35kV rms. The surface morphological investigation of PCL/CHX antimicrobial nanofibers confirmed that smooth beadless nanofibers have been obtained. Fiber diameter and viscosity were increasing with respect to PCL/CHX concentrations.

Remodeling of inherent antimicrobial nanofiber dressings with melamine-modified fibroin into neoskin

A melamine-modified fibroin was synthesized and fabricated into electrospun nanofiber films with broad-spectrum antimicrobial activity, sustained water retention, and fast reepithelialization and revascularization.

Combating Microbial Contamination with Robust Polymeric Nanofibers: Elemental Effect on the Mussel-Inspired Cross-Linking of Electrospun Gelatin

Designing biocompatible nanofibrous mats capable of preventing microbial colonization from resident and nosocomial bacteria for an extended period remains an unmet clinical need. In the present work, we designed antibiotic free durable antimicrobial nanofiber mats by taking advantage of synergistic interactions between polydopamine (pDA) and metal ions with varying degree of antimicrobial properties (Ag+, Mg2+, Ca2+, and Zn2+). Microscopic analysis showed successful pDA-mediated cross-linking of the gelatin nanofibers, which further improved by the inclusion of Ag+, Mg2+, and Ca2+ ions as supported by mechanical and thermal studies. Spectroscopic results reinforce the presence of strong interactions between pDA and metal ions in the composite nanofibers, leading to generation of robust polymeric nanofibers. We further showed that strong pDA-Ag interactions attenuated the cell cytotoxicity and anticell proliferative properties of silver ions for immortalized keratinocytes and primary human dermal fibroblasts. pDA-Ca2+/Zn2+ interactions rendered the composite structure sterile against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium strains, whereas the silver ion-incorporated composite mats displayed broad spectrum antibacterial activity against both Gram-positive/-negative bacteria and yeast strains. We showed that the strong pDA-Ag interactions help retaining long-term antimicrobial activity of the mats for at least 40 days while attenuating mammalian cell cytotoxicity of silver ions for skin cells. Overall, the results suggest the potential of pDA-metal ion interactions for engineering sterile nanofibrous mats and expanding the antibiotic armamentarium against drug-resistant pathogens.

Novel Inorganic-Based N-Halamine Nanofibrous Membranes As Highly Effective Antibacterial Agent for Water Disinfection.

Novel superhydrophilic inorganic-based N-halamine nanofibrous membranes with high active chlorine contents, outstanding rechargeability, favorable water swelling resistance, and superior mechanical performance were prepared through the combination of electrospinning and sol-gel processing, which could be applied to the dynamic disinfection of bacteria-contaminated water with high disinfection efficiency, large processing flux, and long-term durability. The successful preparation of such silica nanofiber membranous N-halamine antimicrobial with intriguing properties would provide the reference for developing novel antimicrobial nanofibers for multifunctional applications.

Electrospun thyme essential oil/gelatin nanofibers for active packaging against Campylobacter jejuni in chicken

Campylobacter jejuni (C. jejuni) contamination on poultry surface posed great threats to meat industry and human health. In order to control the propagation of C. jejuni, the gelatin nanofibers containing thyme essential oil/β-cyclodextrin ε-polylysine nanoparticles (TCPNs) were engineered. Firstly, TCPNs were successfully fabricated via ionic gelation. The prepared TCPNs showed excellent antimicrobial activity against C. jejuni, which caused membranolysis and protein leakage of C. jejuni. Subsequently, TCPNs were incorporated into gelatin nanofibrous matrix via electrospinning to produce antimicrobial nanofibers. Uniformly disordered fibrous structure with good continuity and fine diameter distribution was observed. Finally, the aerobic bacterial count, thiobarbituric acid, total volatile basic nitrogen, pH, color and texture of meat samples packaged with the nanofibers were detected. The results implied the TCPNs embedded gelatin nanofibers had a promising prospect in meat preservation without impact on sensory evaluation.

Fabrication and Microscopic and Spectroscopic Characterization of Cytocompatible Self-Assembling Antimicrobial Nanofibers

The discovery of antimicrobial peptides (AMPs) has brought tremendous promise and opportunities to overcome the prevalence of bacterial resistance to commonly used antibiotics. However, their widespread use and translation into clinical application is hampered by the moderate to severe hemolytic activity and cytotoxicity. Here, we presented and validated a supramolecular platform for the construction of hemo- and cytocompatible AMP-based nanomaterials, termed self-assembling antimicrobial nanofibers (SAANs). SAANs, the "nucleus" of our antimicrobial therapeutic platform, are supramolecular assemblies of de novo designed AMPs that undergo programmed self-assembly into nanostructured fibers to "punch holes" in the bacterial membrane, thus killing the bacterial pathogen. In this study, we performed solid-state NMR spectroscopy showing predominant antiparallel β-sheet assemblies rather than monomers to interact with liposomes. We investigated the mode of antimicrobial action of SAANs using transmission electron microscopy and provided compelling microscopic evidence that self-assembled nanofibers were physically in contact with bacterial cells causing local membrane deformation and rupture. While effectively killing bacteria, SAANs, owing to their nanoparticulate nature, were found to cross mammalian cell membranes harmlessly with greatly reduced membrane accumulation and possess exceptional cytocompatibility and hemocompatibility compared to natural AMPs. Through these systematic investigations, we expect to establish this new paradigm for the customized design of SAANs that will provide exquisite, tunable control of both bactericidal activity and cytocompatibility and can potentially overcome the drawbacks of traditional AMPs.

Antibacterial activity of PEO nanofibers incorporating polysaccharide from dandelion and its derivative

A water-soluble antibacterial polysaccharide from dandelions (PD) was chemically modified to obtain its carboxymethylated derivative (CPD). The degree of substitution of CPD was 0.455. Fourier transform infrared (FTIR) spectra analysis, zeta potential, particle size and rheological test verified the carboxymethylation of PD, accompanying with the change of physicochemical properties. Moreover, Listeria monocytogenes treated with 10 mg/mL PD and CPD achieved 1.96 and 3.29 log CFU/mL reduction in population, respectively. Subsequently, PD and CPD were incorporated into polyethylene oxide (PEO) nanofiber matrix to fabricate antimicrobial nanofibers. The prepared nanofibers were characterized by scanning electron microscope, atomic force microscope and FTIR. Finally, both PD/PEO and CPD/PEO nanofibers exhibited favourable antibacterial effect on L. monocytogenes, with an improved antibacterial activity of CPD/PEO nanofibers than PD/PEO nanofibers. In conclusion, this study demonstrated PD and CPD could be applied to the fabrication of antibacterial food packaging.

Production and Characterization of Antimicrobial Electrospun Nanofibers Containing Polyurethane, Zirconium Oxide and Zeolite

In this study, electrospinning technique has been utilized to prepare composite nanofiber mats of polyurethane (PU)/zirconium dioxide (ZrO2) and PU/zeolite, consisted by antimicrobial properties. Tensile strength measurement test was performed for the mechanical analysis of the nanofibers. Scanning electron microscopy (SEM) were performed for displaying the morphological features of the fiber structure. XRD tests were performed for revealing the chemical structure. Antimicrobial tests were also performed to display antimicrobial effects of the produced materials. In vitro test was also performed to determine cytotoxicity and biocompatibility. The present PU/ZrO2 and PU/zeolite composite nanofibers resulted with improved mechanical properties and good antimicrobial properties against either their pure forms or other studies. Cell proliferation and viability also increased significantly with increase in zeolite and ZrO2 ratio. It is concluded that this composition provides a novel alternative as an antimicrobial material which can be suitable as a wound dressing or a coating material for various healthcare engineering applications.