Preparation of antimicrobial poly(vinyl alcohol) nanofibers containing silver nanoparticles

Polyvinyl alcohol (PVA) nanofibers containing Ag nanoparticles were prepared by electrospinning PVA/silver nitrate (AgNO₃) aqueous solutions, followed by short heat treatment, and their antimicrobial activity was investigated for wound dressing applications. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for the preparation of wound dressing nanofibers. After heat treatment at 155 °C for 3 min, the PVA/AgNO₃ nanofibers became insoluble, while the Ag⁺ ions therein were reduced so as to produce a large number of Ag nanoparticles situated preferentially on their surface. The residual Ag⁺ ions were reduced by subsequent UV irradiation for 3 h. The average diameter of the Ag nanoparticles after the heat treatment was 5.9 nm and this value increased slightly to 6.3 nm after UV irradiation. It was found that most of the Ag⁺ ions were reduced by the simple heat treatment. The PVA nanofibers containing Ag nanoparticles showed very strong antimicrobial activity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2468–2474, 2006     

Thermal and morphological investigation of the effect of POSS-(PEG2000)8 addition to UV curable PEGMEA/PEGDA formulation and simultaneously in situ formed silver nanoparticles

In this study, hybrid nanocomposites were synthesized by photo-crosslinking of poly (ethylene glycol) methyl ether acrylate/poly (ethylene glycol) diacrylate monomer system using 2- (carboxymethoxy) thioxanthone and POSS-(PEG₂₀₀₀)₈. Additionally, AgNO₃ was added to this formulation and in situ formation of silver nanoparticles onto hybrid nanocomposites were achieved in one-step. UV–Vis spectroscopy technique was used as a very useful tool for surface plasmon resonance band detection of silver nanoparticles. In addition to thermogravimetric analyses which were performed in nitrogen atmosphere to determine the thermal stability of the nanocomposites, dynamic light scattering, and scanning electron microscopy techniques were also used for size and morphology of silver nanoparticles in a hybrid network. TGA analyses proved that even the addition of a very low amount of POSS-(PEG₂₀₀₀)₈ made noteworthy contribution to thermal stability especially in the presence of silver nanoparticles in the hybrid network. The swelling capacities of the prepared films were examined at 1, 3 and 24 h in phosphate buffer solution (pH = 7.4). It was found that film containing only POSS-(PEG₂₀₀₀)₈ had the highest swelling ratio in the shortest time.     

Colloid‐Electrospinning: Fabrication of Multicompartment Nanofibers by the Electrospinning of Organic or/and Inorganic Dispersions and Emulsions

Solution‐, melt‐, and co‐axial electrospinning are well‐known methods for producing nano‐ and microfibers. The electrospinning of colloids (or colloid‐electrospinning) is a new field that offers the possibility to elaborate multicompartment nanomaterials. However, the presence of colloids in the electrospinning feed further complicates theoretical predictions in a system that is dependent on chemical, physical, and process parameters. Herein, we give a summary of recent important results and discuss the perspectives of electrospinning of colloids for the synthesis and characterization of multicompartment fibers.     

Mechanism of Producing Metallic Nanoparticles,with an Emphasis on Silver and Gold Nanoparticles,Using Bottom-Up Methods

Bottom-up nanoparticle (NP) formation is assumed to begin with the reduction of the precursor metallic ions to form zero-valent atoms. Studies in which this assumption was made are reviewed. The standard reduction potential for the formation of aqueous metallic atoms—E⁰(Mⁿ⁺_aq/M⁰_aq)—is significantly lower than the usual standard reduction potential for reducing metallic ions Mⁿ⁺ in aqueous solution to a metal in solid state. E⁰(Mⁿ⁺_aq/M⁰_solid). E⁰(Mⁿ⁺_aq/M⁰_aq) values are negative for many typical metals, including Ag and Au, for which E⁰(Mⁿ⁺_aq/M⁰_solid) is positive. Therefore, many common moderate reduction agents that do not have significantly high negative reduction standard potentials (e.g., hydrogen, carbon monoxide, citrate, hydroxylamine, formaldehyde, ascorbate, squartic acid, and BH₄⁻), and cannot reduce the metallic cations to zero-valent atoms, indicating that the mechanism of NP production should be reconsidered. Both AgNP and AuNP formations were found to be multi-step processes that begin with the formation of clusters constructed from a skeleton of M⁺-M⁺ (M = Ag or Au) bonds that is followed by the reduction of a cation M⁺ in the cluster to M⁰, to form M_n⁰ via the formation of NPs. The plausibility of M⁺-M⁺ formation is reviewed. Studies that suggest a revised mechanism for the formation of AgNPs and AuNPs are also reviewed.     

Effect of silver nanoparticles on the dynamic crystallization behavior of nylon‐6

The effect of introducing silver nanoparticles on the rheological properties and dynamic crystallization behavior of nylon‐6 was investigated. The nanocomposites showed slightly higher viscosity than pure nylon‐6 in the low‐frequency range even at an extremely low loading level of the silver particles (0.5–1.0 wt %). The nanoparticles had a more noticeable effect on the storage modulus than on the loss modulus of a nylon‐6 melt and reduced its loss tangent. They increased the crystallization temperature of nylon‐6 by about 14 °C and produced a sharper crystalline peak. The silver nanoparticles promoted the crystallization of nylon‐6, and their effect on the dynamic crystallization of nylon‐6 at 200 °C was more notable at a lower shear rate and at 190 °C at a higher frequency. Nylon‐6 produced large spherulitic crystals, but the nanocomposites showed a grainy structure. In addition, the silver nanoparticles reduced the fraction of the α‐form crystal but increased that of the γ‐form crystal. The nanocomposites crystallized at 190 °C showed a lower melting temperature than nylon‐6 by about 3 °C, whereas the nanocomposites crystallized at 200 °C showed almost the same melting temperature. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 790–799, 2004     

Characterization of the Nanoscale Microstructure of an Immersion Silver on Sputtered Copper

1 INTRODUCTION Silver and its compounds have received much attention due to their current and potential applica- tions in many areas[1, 2]. As a metal with the highest electrical and thermal conductivities, silver was one of the most important noble metals used in electrical industries in the last century. Several decades ago, however, the development of silver application in electronic area seemed not so quick. The fear for some undesirable phenomena involving silver, like “electrochemi…     

Enhancement of the Surface Activity for Some Monomeric and Polymeric Thiol Surfactants Using Silver Nanoparticles

In the present work, the self-assembling of some synthesized thiol surfactants namely (6-(3-amino phenoxy) hexane-1-thiol, 8-(3-amino phenoxy) octane-1-thiol, 10-(3-amino phenoxy) decane-1-thiol, 12-(3-amino phenoxy) dodecane-1-thiol, and their polymers on silver nanoparticles was investigated. The self-assembling of these surfactants on silver nanoparticles was characterized using different techniques such as ultraviolet (UV) spectroscopy, powder x-ray diffraction (XRD), electrone diffraction (ED), and transmission electron microscopy (TEM). The effect of the self-assembling of these surfactants on the stabilization of the silver nanoparticles (AgNPs) was studied using TEM images. The growth of the silver nanoparticles was investigated with respect to the increase of alkyl chain in the synthesized thiol surfactants. The effect of silver nanoparticles on the surface, interfacial tension, and the emulsion stability of these surfactants with paraffin oil was studied. The results show that the silver nanoparticles have the ability to effect on the behavior of these surfactants in solution and improve their surface activity.     

Revealing the Distribution of the Atoms within Individual Bimetallic Catalyst Nanoparticles

To be able to correlate the catalytic properties of nanoparticles with their structure, detailed knowledge about their make‐up on the atomic level is required. Herein, we demonstrate how atom‐probe tomography (APT) can be used to quantitatively determine the three‐dimensional distribution of atoms within a Au@Ag nanoparticle with near‐atomic resolution. We reveal that the elements are not evenly distributed across the surface and that this distribution is related to the surface morphology and residues from the particle synthesis.     

Synthesis and Antioxidant Activity of Silver Nanoparticles Using the Odontonema strictum Leaf Extract

The aqueous extract of the leaves of Odontonema strictum (OSM) is used in folk medicine for its antihypertensive properties, and it contains a wide range of secondary metabolites, mostly polyphenols such as verbascoside and isoverbascoside, which could play a major role in the preparation of silver nanoparticles. In this study, we aimed to prepare AgNPs for the first time using the OSM leaf extract (OSM-AgNPs) to investigate their free radical-scavenging potency against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H₂O₂). Dynamic light scattering (DLS), UV/Vis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS) were used to characterize the OSM-AgNPs. With a size around 100 nm and a ζ-potential of −41.1 mV, OSM-AgNPs showed a good stability and a better colloidal property due to electrostatic repulsion and the dispersity. The strong absorption peak at 3 keV in the EDX spectra indicated that silver was the major constituent. Additionally, the existence of silver atoms was confirmed by the Ag 3d_5/2 peak around 367 eV in the XPS spectra. IC₅₀ values of 116 μg/mL and 4.4 μg/mL were obtained for the scavenging activities of DPPH and H₂O₂, respectively. The synthetic OSM-AgNPs can be further exploited as potential antioxidant agents.     

In situ generation of Ag nanoparticles during photopolymerization by using newly developed dyes-based three-component photoinitiating systems and the related 3D printing applications and their shape change behavior

Silver nanoparticles (AgNPs) play a crucial role in biology and medical research as their extensive and efficient antibacterial activity and high electrical and thermal conductivity. However, the generation of them with a certain morphology under mild conditions (under air, solvent-free, room temperature, etc.,) is still a huge challenge. Herein, a simple one-step method is proposed to generate AgNPs in situ at room temperature under air by combining the photopolymerization process with the formation process of AgNPs within a few minutes. In detailed, 12 different dyes based on 2,5-diethylene-cyclopentan-1-one were first synthesized and used as high-performance type II photoinitiator. When using in conjunction of bis-(4-tert-butylphenyl) iodonium hexafluorophosphate (Iod) and ethyl 4-dimethylaminobenzoate (EDB), they can effectively boost the free radical photopolymerization (FRP) of polyethylene glycol diacrylate (PEG-DA) and the cationic photopolymerization (CP) of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (EPOX) upon irradiation with LED@405 nm. Furthermore, all the formulations containing/without AgNPs can be successfully used to perform the direct laser write experiment. However, even if all of the obtained 3D patterns exhibited reversible swelling performance and shape-memory effects caused by swelling and dehydration for the access to 4D printing, the presence of AgNPs will affect these properties.     

Significant enhancement of electrical and thermal conductivities of polyethylene carbon nanotube composites by the addition of a low amount of silver nanoparticles

Electrically and thermally conductive high‐density polyethylene composites filled with hybrid fillers, multiwall carbon nanotubes (MWCNTs) and silver nanoparticles (Ag‐NPs), have been prepared in the melt state. The investigation of their electrical and thermal conductivities while comparing with high‐density polyethylene/MWCNT binary composites shows that the addition of only 3 vol% of Ag‐NPs does not reduce the electrical percolation threshold (P_c) that remains as low as 0.40 vol% of MWCNTs but leads to an increase in the maximum dc electrical conductivity of PE/MWCNT composites by two orders of magnitudes. Moreover, the association of both Ag‐NPs and carbon nanotube particles improved our composite's thermal conductivity. Copyright © 2014 John Wiley & Sons, Ltd.     

Role of stabilizing agents in the formation of stable silver nanoparticles in aqueous solution: Characterization and stability study

The stability of silver nanoparticles is controlled mainly by two major factors, namely, aggregation and oxidation. In the present study, silver nanoparticles were synthesized by using different series of reducing agents like a strong reducing agent (sodium borohydride), a mild reducing agent (tri-sodium citrate), and a weak reducing agent (glucose) with different capping agents, namely, polyvinyl pyrrolidone (PVP K 30), starch, and sodium carboxyl methyl cellulose (NaCMC). The synthesized silver nanoparticles were characterized by UV-Visible absorption spectroscopy, dynamic light scattering (DLS), atomic force microscopy (AFM), and anti-microbial activity. The particle size of silver nanoparticles varies in the following order: sodium borohydride < tri-sodium citrate < glucose. Combination of sodium borohydride–polyvinyl pyrrolidone and tri-sodium citrate-polyvinyl pyrrolidone yields stable silver nanoparticles compared to other combinations of reducing agents and capping agents. The stability results confirmed that a refrigerated condition (8°C) was more suitable for storage of silver nanoparticles. Anti-microbial activity of silver nanoparticles synthesized in a sodium borohydride–polyvinyl pyrrolidone mixture shows a larger zone of inhibition compared to other silver nanoparticles. Anti-microbial results confirmed that the anti-microbial activity is better with smaller particle size. The size and stability of silver nanoparticles in the presence of different combinations of stabilizing and capping agents are reported.     

Electron Transfer in Peptides: On the Formation of Silver Nanoparticles

Some microorganisms perform anaerobic mineral respiration by reducing metal ions to metal nanoparticles, using peptide aggregates as medium for electron transfer (ET). Such a reaction type is investigated here with model peptides and silver as the metal. Surprisingly, Ag⁺ ions bound by peptides with histidine as the Ag⁺‐binding amino acid and tyrosine as photoinducible electron donor cannot be reduced to Ag nanoparticles (AgNPs) under ET conditions because the peptide prevents the aggregation of Ag atoms to form AgNPs. Only in the presence of chloride ions, which generate AgCl microcrystals in the peptide matrix, does the synthesis of AgNPs occur. The reaction starts with the formation of 100 nm Ag@AgCl/peptide nanocomposites which are cleaved into 15 nm AgNPs. This defined transformation from large nanoparticles into small ones is in contrast to the usually observed Ostwald ripening processes and can be followed in detail by studying time‐resolved UV/Vis spectra which exhibit an isosbestic point.     

Microwave-Assisted Green Synthesis of Non-Cytotoxic Silver Nanoparticles Using the Aqueous Extract of Rosa santana (rose) Petals and Their Antimicrobial Activity

Green methods using biological extracts, in particular plant-based solutions, have shown great potential for silver nanoparticle synthesis. A microwave-assisted single-step phytosynthesis of silver nanoparticles is described in the present study. The aqueous extract obtained from the Rosa santana (rose) petals was used for the first time in the synthesis. The synthesized nanoparticles obtained after optimized microwave conditions for time and temperature were analyzed by ultraviolet–visible spectroscopy (UV–Vis), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Zeta-size analysis. The results obtained from the characterization studies showed that the synthesized nanoparticles were nearly spherical in shape with sizes from 6.52?nm to 25.24?nm with an average particle size of 14.48?nm with a face-centered cubic structure. The antibacterial activities of the synthesized nanoparticles were evaluated and revealed that the silver nanoparticles displayed good inhibition against both Gram-negative and Gram-positive bacteria. Also, the cytotoxic effect of the silver nanoparticles on a mouse fibroblast cell line (L929) was studied by a cell viability assay. The results showed that phytosynthesized silver nanoparticles were nontoxic to the healthy normal cell line at all tested concentrations.     

Green Synthesis of Silver Nanoparticles Using the Plant Extract of Acer oblongifolium and Study of Its Antibacterial and Antiproliferative Activity via Mathematical Approaches

In this study, the antibacterial and antifungal properties of silver nanoparticles synthesized with the aqueous plant extract of Acer oblongifolium leaves were defined using a simplistic, environmentally friendly, reliable, and cost-effective method. The aqueous plant extract of Acer oblongifolium, which served as a capping and reducing agent, was used to biosynthesize silver nanoparticles. UV visible spectroscopy, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and scanning electron microscopy were used to analyze the biosynthesized Acer oblongifolium silver nanoparticles (AgNPs). Gram-positive bacteria (Bacillus paramycoides and Bacillus cereus) and Gram-negative bacteria (E. coli) were used to test the AgNPs’ antibacterial activity. The presence of different functional groups was determined by FTIR. The AgNPs were rod-like in shape. The nanoparticles were more toxic against Escherichia coli than both Bacillus cereus and Bacillus paramycoides. The AgNPs had IC₅₀ values of 6.22 and 9.43 and mg/mL on HeLa and MCF-7, respectively, proving their comparatively strong potency against MCF-7. This confirmed that silver nanoparticles had strong antibacterial activity and antiproliferative ability against MCF-7 and HeLa cell lines. The mathematical modeling revealed that the pure nanoparticle had a high heat-absorbing capacity compared to the mixed nanoparticle. This research demonstrated that the biosynthesized Acer oblongifolium AgNPs could be used as an antioxidant, antibacterial, and anticancer agent in the future.     

Exploring the Antibacterial and Antibiofilm Efficacy of Silver Nanoparticles Biosynthesized Using Punica granatum Leaves

The current research work illustrates an economical and rapid approach towards the biogenic synthesis of silver nanoparticles using aqueous Punica granatum leaves extract (PGL-AgNPs). The optimization of major parameters involved in the biosynthesis process was done using Box-Behnken Design (BBD). The effects of different independent variables (parameters), namely concentration of AgNO₃, temperature and ratio of extract to AgNO_3, on response viz. particle size and polydispersity index were analyzed. As a result of experiment designing, 17 reactions were generated, which were further validated experimentally. The statistical and mathematical approaches were employed on these reactions in order to interpret the relationship between the factors and responses. The biosynthesized nanoparticles were initially characterized by UV-vis spectrophotometry followed by physicochemical analysis for determination of particle size, polydispersity index and zeta potential via dynamic light scattering (DLS), SEM and EDX studies. Moreover, the determination of the functional group present in the leaves extract and PGL-AgNPs was done by FTIR. Antibacterial and antibiofilm efficacies of PGL-AgNPs against Gram-positive and Gram-negative bacteria were further determined. The physicochemical studies suggested that PGL-AgNPs were round in shape and of ~37.5 nm in size with uniform distribution. Our studies suggested that PGL-AgNPs exhibit potent antibacterial and antibiofilm properties.     

Green Synthesis of Silver Nanoparticles Using Aerial Part Extract of the Anthemis pseudocotula Boiss. Plant and Their Biological Activity

Green syntheses of metallic nanoparticles using plant extracts as effective sources of reductants and stabilizers have attracted decent popularity due to their non-toxicity, environmental friendliness and rapid nature. The current study demonstrates the ecofriendly, facile and inexpensive synthesis of silver nanoparticles (AP-AgNPs) using the extract of aerial parts of the Anthemis pseudocotula Boiss. plant (AP). Herein, the aerial parts extract of AP performed a twin role of a reducing as well as a stabilizing agent. The green synthesized AP-AgNPs were characterized by several techniques such as XRD, UV-Vis, FT-IR, TEM, SEM and EDX. Furthermore, the antimicrobial and antibiofilm activity of as-prepared AP-AgNPs were examined by a standard two-fold microbroth dilution method and tissue culture plate methods, respectively, against several Gram-negative and Gram-positive bacterial strains and fungal species such as Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), multidrug-resistant Pseudomonas aeruginosa (MDR-PA) and Acinetobacter baumannii (MDR-AB), methicillin-resistant S. aureus (MRSA) and Candida albicans (C. albicans) strains. The antimicrobial activity results clearly indicated that the Gram-negative bacteria MDR-PA was most affected by AgNPs as compared to other Gram-negative and Gram-positive bacteria and fungi C. albicans. Whereas, in the case of antibiofilm activity, it has been found that AgNPs at 0.039 mg/mL, inhibit biofilms formation of Gram-negative bacteria i.e., MDR-PA, E. coli, and MDR-AB by 78.98 ± 1.12, 65.77 ± 1.05 and 66.94 ± 1.35%, respectively. On the other hand, at the same dose (i.e., 0.039 mg/mL), AP-AgNPs inhibits biofilm formation of Gram-positive bacteria i.e., MRSA, S. aureus and fungi C. albicans by 67.81 ± 0.99, 54.61 ± 1.11 and 56.22 ± 1.06%, respectively. The present work indicates the efficiency of green synthesized AP-AgNPs as good antimicrobial and antibiofilm agents against selected bacterial and fungal species.