Fabrication of nanofibers with antimicrobial functionality used as filters: protection against bacterial contaminants

A comparative study of antimicrobial activity is done using three different electrospun nanofibers namely-CA, PAN, and PVC used as control and with various amounts of AgNO(3) being treated with UV-irradiation leading to the enhancement of silver nanoparticles. DMF is used as the common solvent which helps to undergo spontaneous slow reduction at room temperature to form silver nanoparticles followed by UV-irradiation using a 400 W source. The time required for the formation of silver nanoparticles is short and they are more or less well dispersed with few such aggregates. The presence of silver nanoparticles is confirmed using various characterization techniques. The antimicrobial activity is studied using nanofibers with fabricated functionality.     

Antimicrobial cellulose acetate nanofibers containing silver nanoparticles

It was found for the first time that polymer nanofibers containing Ag nanoparticles on their surface could be produced by UV irradiation of polymer nanofibers electrospun with small amounts of silver nitrate (AgNO₃). When the cellulose acetate (CA) nanofibers electrospun from CA solutions with 0.5 wt% of AgNO₃ were irradiated with UV light at 245 nm, Ag nanoparticles were predominantly generated on the surface of the CA nanofibers. The number and size of the Ag nanoparticles were continuously increased up to 240 min. The Ag⁺ ions and Ag clusters diffused and aggregated on the surface of the CA nanofibers during the UV irradiation. The Ag nanoparticles with an average size of 21 nm exhibited strong antimicrobial activity.     

Silver glyconanoparticles functionalized with sugars of sweet sorghum syrup as an antimicrobial agent

Bio-directed synthesis of metal nanoparticles is gaining importance due to their biocompatibility, low toxicity and eco-friendly nature. We used sweet sorghum syrup for a facile and cost-effective green synthesis of silver glyconanoparticles. Silver nanoparticles were formed due to reduction of silver ions when silver nitrate solution was treated with sorghum syrup solutions of different pH values. The nanoparticles were characterized by UV–vis, TEM (transmission electron microscopy), DLS (dynamic light scattering), EDAX (energy dispersive X-ray spectroscopy), FT-IR (fourier transform infrared spectroscopy) and XRD (X-ray diffraction spectroscopy). The silver glyconanoparticles exhibited a characteristic surface plasmon resonance around 385 nm. At pH 8.5, the nanoparticles were mono-dispersed and spherical in shape with average particle size of 11.2 nm. The XRD and SAED studies suggested that the nanoparticles were crystalline in nature. EDAX analysis showed the presence of elemental silver signal in the synthesized glyconanoparticles. FT-IR analysis revealed that glucose, fructose and sucrose present in sorghum syrup acted as capping ligands. Silver glyconanoparticles prepared at pH 8.5 had a zeta potential of ?28.9 mV and were anionic charged. They exhibited strong antimicrobial activity against Gram-positive, Gram-negative and different Candida species at MIC values ranging between 2 and 32 μg ml^?1. This is first report on sweet sorghum syrup sugars-derived silver glyconanoparticles with antimicrobial property.     

Structure and mechanical properties of wet-spun fibers made from natural cellulose nanofibers

Cellulose nanofibers were prepared by TEMPO-mediated oxidation of wood pulp and tunicate cellulose. The cellulose nanofiber suspension in water was spun into an acetone coagulation bath. The spinning rate was varied from 0.1 to 100 m/min to align the nanofibers to the spun fibers. The fibers spun from the wood nanofibers had a hollow structure at spinning rates of >10 m/min, whereas the fibers spun from tunicate nanofibers were porous. Wide-angle X-ray diffraction analysis revealed that the wood and tunicate nanofibers were aligned to the fiber direction of the spun fibers at higher spinning rates. The wood spun fibers at 100 m/min had a Young's modulus of 23.6 GPa, tensile strength of 321 MPa, and elongation at break of 2.2%. The Young's modulus of the wood spun fibers increased with an increase in the spinning rate because of the nanofiber orientation effect.     

Safety, Formulation and In Vitro Antiviral Activity of the Antimicrobial Peptide Subtilosin Against Herpes Simplex Virus Type 1

In the present study, the antiviral properties of the bacteriocin subtilosin against Herpes simplex virus type 1 (HSV-1) and the safety and efficacy of a subtilosin-based nanofiber formulation were determined. High concentrations of subtilosin, the cyclical antimicrobial peptide produced by Bacillus amyloliquefaciens, were virucidal against HSV-1. Interestingly, at non-virucidal concentrations, subtilosin inhibited wild type HSV-1 and aciclovir-resistant mutants in a dose-dependent manner. Although the exact antiviral mechanism is not fully understood, time of addition experiments and western blot analysis suggest that subtilosin does not affect viral multiplication steps prior to protein synthesis. Poly(vinyl alcohol)-based subtilosin nanofibers with a width of 278 nm were produced by the electrospinning process. The retained antimicrobial activity of the subtilosin-based fibers was determined via an agar well diffusion assay. The loading capacity of the fibers was 2.4 mg subtilosin/g fiber, and loading efficiency was 31.6 %. Furthermore, the nanofibers with and without incorporated subtilosin were shown to be non-toxic to human epidermal tissues using an in vitro human tissue model. Taking together these results, subtilosin-based nanofibers should be further studied as a novel alternative method for treatment and/or control of HSV-1 infection.     

Electrospun chitosan-graft-poly (ε -caprolactone)/poly (ε-caprolactone) cationic nanofibrous mats as potential scaffolds for skin tissue engineering

This research is aimed to develop cationic nanofibrous mats with improved cellular adhesion profiles and stability of three-dimensional fibrous structure as potential scaffolds for skin tissue engineering. Firstly, amino-remained chitosan-graft-poly (?-caprolactone) (CS-g-PCL) was synthesized with a facile one-step manner by grafting ?-caprolactone oligomers onto the hydroxyl groups of CS via ring-opening polymerization by using methanesulfonic acid as solvent and catalyst. And then, CS-g-PCL/PCL nanofibrous mats were obtained by electrospinning of CS-g-PCL/PCL mixed solution. Scanning electron microscopy (SEM) images showed that the morphologies and diameters of the nanofibers were mainly affected by the weight ratio of CS-g-PCL to PCL. The enrichment of amino groups on the nanofiber surface was confirmed by X-ray photoelectron spectroscopy (XPS). With the increase of CS-g-PCL in CS-g-PCL/PCL nanofiber, the content of amino groups on the nanofiber surface increased, which resulted in the increase of zeta-potential of nanofibers. Studies on cell-scaffold interaction were carried out by culturing mouse fibroblast cells (L929) on CS-g-PCL/PCL nanofibrous mats with various contents of CS-g-PCL by assessing the growth, proliferation and morphologies of cells. The results of MTS assay and SEM observation showed that CS-g-PCL/PCL (2/8) mats with a moderate surface zeta-potential (ζ=3mV) were the best in promoting the cell attachment and proliferation. Toluidine blue staining further confirmed that L929 cells grew well and exhibited a normal morphology on the CS-g-PCL/PCL (2/8) mats. These results suggested the potential utilization of CS-g-PCL/PCL (2/8) nanofibrous mats for skin tissue engineering.     

Curcumin nanofibers for the purpose of wound healing

Poor wound healing is a highly prevalent clinical problem with, as yet, no entirely satisfactory solution. A new technique, termed electrospinning, may provide a solution to improve wound healing. Due to their large surface area to volume ratio and porosity, the nanofibers created by electrospinning are able to deliver sustained drug release and oxygen to the wound. Using different types of polymers with varying properties helps strengthening nanofiber and exudates absorption. The nanofibers appear to have an ideal structure applicable for wound healing and, in combination with curcumin, can blend the anti-inflammatory and antioxidant properties of curcumin into a highly effective wound dressing. The use of suitable curcumin solvents and the slow release of curcumin from the nanofiber help in overcoming the known limitations of curcumin, specifically its low stability and limited bioavailability. Here, we review the studies which have been done on synthesized nanofibers containing curcumin, produced by the electrospinning technique, for the purpose of wound healing.     

Anticancer,antimicrobial, antioxidant,and catalytic activities of green-synthesized silver and gold nanoparticles using Bauhinia purpurea leaf extract

The synthesis of metal nanoparticles by green methods attained enormous attention in recent years due to its easiness, non-toxicity, and eco-friendly nature. In the present study, noble metal nanoparticles such as silver and gold were prepared using an aqueous leaf extract of a medicinal plant, Bauhinia purpurea. The leaf extract performed as both reducing and stabilizing agents for the development of nanoparticles. The formations of silver and gold nanoparticles were confirmed by observing the surface plasmon resonance peaks at 430 nm and 560 nm, respectively, in UV–Vis absorption spectrum. Various properties of nanoparticles were demonstrated using the characterization techniques such as FTIR, XRD, TEM, and EDX. The synthesized silver and gold nanoparticles had a momentous anticancer effect against lung carcinoma cell line A549 in a dose-dependent manner with IC₅₀ values of 27.97 µg/mL and 36.39 µg/mL, respectively. The antimicrobial studies of synthesized nanoparticles were carried out by agar well diffusion method against six microbial strains. Silver and gold nanoparticles were also showed high antioxidant potentials with IC₅₀ values of 42.37 µg/mL and 27.21 µg/mL, respectively; it was measured using DPPH assay. Additionally, the nanoparticles were observed to be good catalysts for the reduction of organic dyes.

     

Self-assembly of amylose-grafted carboxymethyl cellulose

In this study, we performed the self-assembly of the amylose-grafted carboxymethyl cellulose sodium salt (NaCMC) for the formation of nanofiber films under aqueous conditions. The introduction of amylose graft chains was conducted by the chemoenzymatic approach including phosphorylase-catalyzed enzymatic polymerization. The product had the rigid NaCMC main chain, which further assembled leading to nanofibers by the formation of double helix between the long amylose graft chains in the intermolecular NaCMC chains of the products. The lengths of the fibers were depended on degrees of polymerization of amylose chains. The nanofiber films were constructed by drying the alkaline solutions of the amylose-grafted NaCMC. The lengths of the nanofibers strongly affected their arrangements in the films. The nanofibers were merged further by washing out alkali to produce the robust nanofiber films.     

Rapid biosynthesis of PVP coated silver nanoparticles by <Emphasis Type="Italic">Kocuria rosea</Emphasis> and their antimicrobial activity

The need for more effective antimicrobial agent and propitious application of nanotechnology in therapeutics and diagnostics has prompted the research on ecofriendly synthesis of silver nanoparticles. The objective of present study was to investigate the antibacterial and antifungal activity of biologically synthesized silver nanoparticles. The silver nanoparticles were synthesized by extracellular method, using soil bacteria Kocuria rosea. The synthesized silver nanoparticles were characterized by UV-Visible spectroscopy, X-ray diffractometry (XRD), transmission electron microscopy (TEM) and fourier transformation infrared spectroscopy (FTIR). On the basis of TEM analysis, the synthesized nanoparticles were found to be spherical with an average size of 30–50 nm. The biologically synthesized silver nanoparticles showed significant antimicrobial activity against pathogens.     

Antibacterial activity and interaction mechanism of electrospun zinc-doped titania nanofibers

In this study, a biological evaluation of the antimicrobial activity of Zn-doped titania nanofibers was carried out using Escherichia coli ATCC 52922 (Gram negative) and Staphylococcus aureus ATCC 29231 (Gram positive) as model organisms. The utilized Zn-doped titania nanofibers were prepared by the electrospinning of a sol–gel composed of zinc nitrate, titanium isopropoxide, and polyvinyl acetate; the obtained electrospun nanofibers were vacuum dried at 80°C and then calcined at 600°C. The physicochemical properties of the synthesized nanofibers were determined by X-ray diffraction pattern, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron probe microanalysis, thermogravimetry, and transmission electron microscopy (TEM). The antibacterial activity and the acting mechanism of Zn-doped titania nanofibers against bacteria were investigated by calculation of minimum inhibitory concentration and analyzing the morphology of the bacterial cells following the treatment with nanofibers solution. Our investigations reveal that the lowest concentration of Zn-doped titania nanofibers solution inhibiting the growth of S. aureus ATCC 29231 and E. coli ATCC 52922 strains is found to be 0.4 and 1.6 μg/ml, respectively. Furthermore, Bio-TEM analysis demonstrated that the exposure of the selected microbial strains to the nanofibers led to disruption of the cell membranes and leakage of the cytoplasm. In conclusion, the combined results suggested doping promotes antimicrobial effect; synthesized nanofibers possess a very large surface-to-volume ratio and may damage the structure of the bacterial cell membrane, as well as depress the activity of the membranous enzymes which cause bacteria to die in due course.     

Synthesis and antimicrobial studies of silver N-heterocyclic carbene complexes bearing a methyl benzoate substituent

Due to the properties of silver as an antimicrobial, our research group has synthesized many different silver carbene complexes. Two new silver N-heterocyclic carbene complexes derived from 4,5-dichloroimidazole and theobromine bearing methyl benzoate substituents were synthesized by in situ carbene formation using silver acetate as the base in the reaction. The new compounds were fully characterized by several methods including NMR spectroscopy and X-ray crystallography. Preliminary antimicrobial efficacy studies against Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli were conducted. The results of this study demonstrated antimicrobial efficacy of the two complexes comparable to silver nitrate, showing their potential for use in the treatment of bacterial infections.     

Unique natural-protein hollow-nanofiber membranes produced by weaver ants for medical applications

We report the properties of unique natural-protein hollow-nanofiber membranes produced by weaver ants (Oecophylla smaragdina) and the potential of using the nanofiber membranes for medical applications. Although natural proteins such as silk and collagen have been used to produce electrospun nanofibers for medical applications, there are no reports on producing hollow nanofibers from proteins. Hollow nanofibers are expected to have unique properties such as high drug loading. Weaver ant larvae extrude proteins in the form of nanofibers that are hollow and the adult ants build the nests using the hollow nanofibers. It was found that the nanofiber membranes are composed of fibers with average diameters of 450 nm. The membranes have tensile strength of about 4 MPa, high elongation of about 31% and modulus of 31 MPa, better than any protein nanofiber membrane reported so far. The membranes withstand rigorous boiling in weak alkali, show good attachment and proliferation of osteoblasts and can load up to 4.7 times higher drugs compared to common silk. These features make ant nanofiber membranes unique and preferable for medical and biotechnology industries.     

Fine structure and enzymatic degradation of poly[(R)-3-hydroxybutyrate] and stereocomplexed poly(lactide) nanofibers

Fiber morphology and crystalline structure of poly[(R)-3-hydroxybutyrate] (P(3HB)) and stereocomplexed poly(lactide) (PLA) nanofibers were investigated by using scanning and transmission electron microscopies and X-ray and electron diffractions. In the P(3HB) nanofibers spun from less than 1 wt% 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solution, planar zigzag conformation (beta-form) as well as 2(1) helix conformation (alpha-form) structure was formed. Based on the electron diffraction measurement of single P(3HB) nanofiber, it was revealed that the molecular chains of P(3HB) align parallel to the fiber direction. From the enzymatic degradation test of P(3HB) nanofiber, it was shown that beta-form molecular chains are degraded more preferentially than alpha-form chains. Stereocomplexed PLA nanofibers were electrospun from 1 wt% poly(l-lactide)/poly(d-lactide) (PLLA/PDLA) solution in HFIP, which contains equal amounts of PLLA and PDLA. While as-spun stereocomplexed PLA nanofiber was amorphous, PLA nanofiber annealed at 100 degrees C contained only racemic crystal. It was supposed that the crystallization behavior of stereocomplexed PLA in the nanofiber is affected by the electrospinning process, which forcibly exerts the strain onto the polymer chains.     

Minimal In Vitro Antimicrobial Efficacy and Ocular Cell Toxicity from Silver Nanoparticles

Silver in various forms has long been recognized for antimicrobial properties, both in biomedical devices and in eyes. However, soluble drugs used on the ocular surface are rapidly cleared through tear ducts and eventually ingested, resulting in decreased efficacy of the drug on its target tissue and potential concern for systemic side effects. Silver nanoparticles were studied as a source of anti-microbial silver for possible controlled-release contact lens controlled delivery formulations. Silver ion release over a period of several weeks from nanoparticle sources of various sizes and doses was evaluated in vitro against Pseudomonas aeruginosa strain PAO1. Mammalian cell viability and cytokine expression in response to silver nanoparticle exposure is evaluated using corneal epithelial cells and eye-associated macrophages cultured in vitro in serum-free media. Minimal microcidal and cell toxic effects were observed for several silver nanoparticle suspensions and aqueous extraction times for bulk total silver concentrations commensurate with comparative silver ion (e.g., ) toxicity. This indicates that (1) silver particles themselves in these size ranges (20–60 nm diameter) are not microcidal under conditions tested, and (2) insufficient silver ion is generated from these particles at these silver ion-equivalent loadings to produce observable biological effects compared to silver ions in these in vitro assays. This is consistent with confounding literature describing both efficacy and lack of microcidal effects for silver nanoparticles, depending on milieu, surface oxide properties, and size. If dosing allows substantially increased silver particle loading in the lens to produce sufficient pathogen-toxic silver ions and/or particle-microbe direct contact, the bactericidal efficacy of silver nanoparticles in vitro could possibly limit bacterial colonization problems associated with extended-wear contact lenses.     

Synthesis of Ag-liposome nano composites

Silver nanoparticles were synthesized and stabilized by a simple, environment-friendly method in a liposomes structure. Liposomes were prepared by facing lecithin to the aqueous-phase solutions while stirring vigorously. The ratio of lecithin concentration to silver nitrate (K_Lec/Ag?=?[Lecithin]/[AgNO₃]) is the influencing factor in the synthesis of silver nanoparticles. The stability, size distribution, and antibacterial properties of synthesized silver nanoparticles were studied by ultraviolet (UV)-visible, dynamic light scattering, and antibacterial assay. The UV spectra indicated a single symmetric extinction peak at 400?nm, confirming the spherical shape of the synthesized silver nanoparticles. A high K_Lec/Ag value leads to a reduction in the intensity of extinction spectra and increases the size of Ag-liposomes nanocomposites. The large Ag-liposomes nanocomposites are transformed to the smaller Ag-liposomes nanocomposites (from 342 to 190?nm) due to sonication treatment. The stabilized silver nanoparticles with various lecithin concentrations showed a good antibacterial activity against Staphylococcus aureus, a Gram-positive bacterium, and Escherichia coli, a Gram-negative bacterium.     

Incorporation of the Tat cell‐penetrating peptide into nanofibers improves the respective antitumor immune response

A major challenge for the development of anticancer vaccines is the induction of a safe and effective immune response, particularly mediated by CD8+ T lymphocytes, in an adjuvant‐free manner. In this respect, we present a simple strategy to improve the specific CD8+ T cell responses using KFE8 nanofibers bearing a Class I (Kb)‐restricted peptide epitope (called E. nanofibers) without the use of adjuvant. We demonstrate that incorporation of Tat, a cell‐penetrating peptide (CPP) of the HIV transactivator protein, into E. nanofibers remarkably enhanced tumor‐specific CD8+ T cell responses. E. nanofibers containing 12.5% Tat peptide (E.Tat_12.5 nanofiber) increased antigen cross‐presentation by bone marrow‐derived dendritic cells as compared with E. nanofibers, or E. nanofibers containing 25 or 50% the Tat peptide. Uptake of KFE8.Tat_12.5 nanofibers by dendritic cells (DCs) was significantly increased compared with KFE8 nanofiber lacking Tat. Peritoneal and lymph node DCs of mice immunized with E.Tat_12.5 nanofibers exhibited increased presentation of the H2kb‐epitope (reminiscent for cross‐presentation) compared with DCs obtained from E. nanofiber vaccinated mice. Tetrameric and intracellular cytokine staining revealed that vaccination with E.Tat_12.5 triggered a robust and specific CD8+ T lymphocyte response, which was more pronounced than in mice vaccinated with E. nanofibers alone. Furthermore, E.Tat_12.5 nanofibers were more potent than E. nanofiber to induce antitumor immune response and tumor‐infiltrating IFN‐γ CD8 T lymphocyte. In terms of cancer vaccine development, we propose that harnessing the nanofiber‐based vaccine platform with incorporated Tat peptide could present a simple and promising strategy to induce highly effective antitumor immune response.     

A direct detection of Escherichia coli genomic DNA using gold nanoprobes

Background

Electrospun nanofibers have been widely used as substrata for mammalian cell culture owing to their structural similarity to natural extracellular matrices. Structurally consistent electrospun nanofibers can be produced with synthetic polymers but require chemical modification to graft cell-adhesive molecules to make the nanofibers functional. Development of a facile method of grafting functional molecules on the nanofibers will contribute to the production of diverse cell type-specific nanofiber substrata.

Results

Small molecules, peptides, and functionalized gold nanoparticles were successfully incorporated with polymethylglutarimide (PMGI) nanofibers through electrospinning. The PMGI nanofibers functionalized by the grafted AuNPs, which were labeled with cell-adhesive peptides, enhanced HeLa cell attachment and potentiated cardiomyocyte differentiation of human pluripotent stem cells.

Conclusions

PMGI nanofibers can be functionalized simply by co-electrospinning with the grafting materials. In addition, grafting functionalized AuNPs enable high-density localization of the cell-adhesive peptides on the nanofiber. The results of the present study suggest that more cell type-specific synthetic substrata can be fabricated with molecule-doped nanofibers, in which diverse functional molecules are grafted alone or in combination with other molecules at different concentrations.     

Electrospun poly(epsilon-caprolactone) microfiber and multilayer nanofiber/microfiber scaffolds: characterization of scaffolds and measurement of cellular infiltration

The physical and spatial architectural geometries of electrospun scaffolds are important to their application in tissue engineering strategies. In this work, poly(epsilon-caprolactone) microfiber scaffolds with average fiber diameters ranging from 2 to 10 microm were individually electrospun to determine the parameters required for reproducibly fabricating scaffolds. As fiber diameter increased, the average pore size of the scaffolds, as measured by mercury porosimetry, increased (values ranging from 20 to 45 microm), while a constant porosity was observed. To capitalize on both the larger pore sizes of the microfiber layers and the nanoscale dimensions of the nanofiber layers, layered scaffolds were fabricated by sequential electrospinning. These scaffolds consisted of alternating layers of poly(epsilon-caprolactone) microfibers and poly(epsilon-caprolactone) nanofibers. By electrospinning the nanofiber layers for different lengths of time, the thickness of the nanofiber layers could be modulated. Bilayered constructs consisting of microfiber scaffolds with varying thicknesses of nanofibers on top were generated and evaluated for their potential to affect rat marrow stromal cell attachment, spreading, and infiltration. Cell attachment after 24 h did not increase with increasing number of nanofibers, but the presence of nanofibers enhanced cell spreading as evidenced by stronger F-actin staining. Additionally, increasing the thickness of the nanofiber layer reduced the infiltration of cells into the scaffolds under both static and flow perfusion culture for the specific conditions tested. The scaffold design presented in this study allows for cellular infiltration into the scaffolds while at the same time providing nanofibers as a physical mimicry of extracellular matrix.     

荧光银纳米团簇的生物合成及其在痕量六价铬检测中的应用

[目的]利用季也蒙毕赤酵母ZJC-1合成银纳米团簇并用于痕量Cr(Ⅵ)的检测.[方法]使用经耐银驯化的季也蒙毕赤酵母ZJC-1生物合成荧光银纳米团簇,并对其结构和荧光性能进行了表征,探究Cr(Ⅵ)对银纳米团簇荧光的选择性猝灭作用,建立了银纳米团簇荧光强度与Cr(Ⅵ)浓度的线性关系.同时还考察了体系pH和其他金属离子对C...