Antibacterial effect of silver nanoparticles prepared in bipolymers at moderate temperature

The purpose of this study was to investigate the antibacterial effect of silver nanoparticles in chitosan–poly(ethylene glycol) suspension. The silver nanoparticles (AgNPs) were prepared by use of an environmentally benign method from chitosan (Cts) and poly(ethylene glycol) (PEG) at moderate temperature and with stirring for different times. Silver nitrate (AgNO₃) was used as the metal precursor and Cts and PEG were used as solid support and polymeric stabilizer, respectively. The antibacterial activity of silver–chitosan–poly(ethylene glycol) nanocomposites (Ag–Cts–PEG NCs) against Staphylococcus aureus, Micrococcus luteum, Pseudomonas aeruginosa, and Escherichia coli was tested by use of the Mueller–Hinton agar disk-diffusion method. Formation of AgNPs was determined by UV–visible spectroscopy; surface plasmon absorption maxima were observed at 415–430 nm in the UV–visible spectrum. The peaks in the XRD pattern confirmed that the AgNPs had a face-centered cubic structure; peaks of contaminated crystalline phases were not observed. Transmission electron microscopy (TEM) revealed that the AgNPs synthesized were spherical. The optimum stirring time for synthesis of the smallest particle size (mean diameter 5.50 nm) was 12 h. The AgNPs in Cts–PEG were effective against all the bacteria tested. Higher antibacterial activity was observed for AgNPs with smaller size. These results suggest that AgNPs can be used as an effective inhibitor of bacteria and can be used in medical applications. These results also suggest that AgNPs were successfully synthesized in Cts–PEG suspension at moderate temperature with different stirring times.     

Green synthesis of antibacterial chitosan films loaded with silver nanoparticles

An eco-friendly chemical reduction method was successfully used for the preparation of chitosan (CTS) composite films loaded with silver nanoparticles (AgNPs) by self assembly method using poly(ethylene glycol) as both reducing and stabilizing agent. UV-Vis spectra of the prepared chitosan loaded silver nanoparticles (CTSLAg) films reveal that full reduction of silver ions to silver nanoparticles takes place at 90 °C. The effect of reaction conditions on the silver nanoparticles formation was investigated using UV-Vis spectrophotometer. The morphology of the films was tested by scanning electron microscopy (SEM). The DSC curves showed that the CTSLAg film had a favorable compatibility and heat stability. AgNPs were confirmed by XRD and UV-Vis spectroscopy. The TEM findings revealed that the silver nanoparticles synthesized were spherical in shape with uniform dispersal, and by increasing CTS:PEG ratio larger silver nanoparticles could be obtained. The results of antibacterial study reveal that the prepared nanocomposite films exhibited potential inhibition.     

Multihollow structured poly(methyl methacrylate)/silver nanocomposite microspheres prepared by suspension polymerization in the presence of dual dispersion agents

Poly(methyl methacrylate) (PMMA)/silver nanocomposite microspheres with unique multihollow structures were prepared by suspension polymerization in the presence of dual dispersion agents. The addition of a lipophilic emulsifier, polyethylene glycol (30EO) dipolyhydroxystearate (Arlacel P135), not only stabilized water-in-oil (W/O) emulsion, but also converted silver nanoparticles from hydrophilic to lipophilic. When a suspension polymerization dispersion agent, poly(vinyl alcohol), was added to the above W/O emulsion system, a water-in-oil-in-water suspension was formed with silver nanoparticles dispersed in the oil phase. The suspension polymerization was carried out at low temperature with 2,2’-azobis(2,4-dimethylvaleronitrile) as the initiator. When modified silver nanoparticles were added, the rate of polymerization increased slightly. High monomer conversion (about 85%) was obtained in spite of low polymerization temperature of 30 °C. Under controlled conditions, PMMA/silver microspheres with various hollow structures were synthesized. The PMMA/silver microspheres with multihollow structure showed high antibacterial ability.     

A Green Approach for the Synthesis of Silver Nanoparticles Using Root Extract of <Emphasis Type="Italic">Chelidonium majus:</Emphasis> Characterization and Antibacterial Evaluation

In this study, silver nanoparticles (Ag-NPs) have been synthesized using extract of Chelidonium majus root in aqueous solution at room temperature. The root extract was able to reduce Ag⁺ to Ag⁰ and stabilized the nanoparticles Different physico-chemical techniques including UV–Vis spectroscopy, transmission electron microscopy and powder X-ray diffraction (PXRD) were used for the characterization of the biosynthesized Ag-NPs obtained. The surface plasmon resonance band appeared at 431 nm is an evidence for formation of Ag-NPs. TEM imaging revealed that the synthesized Ag-NPs have an average diameter of around 15 nm and with spherical shape. Moreover the crystalline structure of synthesized nanoparticles was confirmed using XRD pattern. Furthermore antimicrobial activities of synthesized Ag-NPs were evaluated against Escherichia coli -ATCC 25922 and Pseudomonas aeruginosa ATCC 2785 bacteria strain.     

Sustainable fabrication of silver-titania nanocomposites using goji berry (Lycium barbarum L.) fruit extract and their photocatalytic and antibacterial applications

Silver-titania nanocomposites (Ag-TiO₂ NCs) have unique functional attributes due to their photocatalytic and antibacterial properties. In this study, titania nanoparticles (TiO₂-NPs) were successfully in-situ decorated with silver nanoparticles (Ag-NPs) using the aqueous extract of goji berries (Lycium barbarum L.) as a bioreducing and stabilizing agent. Different Ag-TiO₂ NCs were synthesized by treating different concentrations of silver nitrate with a specific concentration of TiO₂-NPs in the presence of fruit extract. The green-synthesized NCs were characterized using several techniques viz., ultraviolet–visible spectrophotometry, X-ray diffractometry (XRD), scanning electron microscopy, field-emission transmission electron microscopy (FE-TEM), Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. XRD analysis revealed the formation of face-centered cubic (fcc) crystals, and FE-TEM analysis revealed the embedment of Ag-NPs throughout the surface of TiO₂-NPs. The average size of Ag-NPs on TiO₂-NPs increased from 11.2 ± 3.05 nm to 16.4 ± 4.5 nm with an increase in the concentration of silver ions, and the morphology of Ag-NPs was predominantly quasi-spherical and hexagonal. These NCs exhibited an excellent photocatalytic degradation of an azo dye, methylene blue (MB). The synthesized Ag-TiO₂ NCs (3:1) showed higher photocatalytic degradation efficiency of ∼ 93.4% for MB in 130 min under visible light irradiation. Ag-TiO₂ NC_S also exhibited good antibacterial activities towards Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). Therefore, the formation of Ag-NPs on the surface of TiO₂-NPs to form Ag-TiO₂ NCs exhibits eco-friendly photocatalytic degradation of azo dye contaminants as well as antibacterial activity.     

Antibacterial properties of novel poly(methyl methacrylate) nanofiber containing silver nanoparticles

Poly(methyl methacrylate) (PMMA) nanofiber containing silver nanoparticles was synthesized by radical-mediated dispersion polymerization and applied to an antibacterial agent. UV-vis spectroscopic analysis indicated that the silver nanoparticles were continually released from the polymer nanofiber in aqueous solution. The antibacterial properties of silver/PMMA nanofiber against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria were evaluated using minimum inhibitory concentration (MIC), the modified Kirby-Bauer method, and a kinetic test. The MIC test demonstrated that the silver/PMMA nanofiber had enhanced antimicrobial efficacy compared to that of silver sulfadiazine and silver nitrate at the same silver concentration.     

Biosynthesis of silver nanoparticles using citrus sinensis peel extract and its antibacterial activity

Biosynthesis of silver nanoparticles (AgNPs) was achieved by a novel, simple green chemistry procedure using citrus sinensis peel extract as a reducing and a capping agent. The effect of temperature on the synthesis of silver nanoparticles was carried out at room temperature (25°C) and 60°C. The successful formation of silver nanoparticles has been confirmed by UV-vis, FTIR, XRD, EDAX, FESEM and TEM analysis and their antibacterial activity against Escherichia coli, Pseudomonas aeruginosa (gram-negative), and Staphylococcus aureus (gram-positive) has been studied. The results suggest that the synthesized AgNPs act as an effective antibacterial agent.     

Copper,gold, and silver decorated magnetic core–polymeric shell nanostructures for destruction of pathogenic bacteria

Fe₃O₄ magnetic nanoparticles (MNPs) were prepared by co-precipitation method. The nanoparticles were silica coated using TEOS, and then modified by the polymeric layers of polypropylene glycol (PPG) and polyethylene glycol (PEG). Finally, the core-shell samples were decorated with Ag, Au, and Cu nanoparticles. The products were characterized by vibrating sample magnetometry (VSM), TGA, SEM, XRD, and FTIR methods. The antibacterial activity of the prepared samples was evaluated in inactivation of E. coli and S. aureus microorganisms, representing the Gram-negative and Gram-positive species, respectively. The effect of solid dosage, bacteria concentration and type of polymeric modifier on the antibacterial activity was investigated. TEM images of the bacteria were recorded after the treatment time and according to the observed changes in the cell wall, the mechanism of antibacterial action was discussed. The prepared nanostructures showed high antibacterial activity against both Gram-negative and Gram-positive bacteria. This was due to the leaching of metal ions which subsequently led to the lysis of bacteria. A theoretical investigation was also done by studying the interaction of loaded metals with the nucleotide components of the microorganism DNA, and the obtained results were used to explain the experimental data. Finally, based on the observed inactivation curves, we explain the antibacterial behavior of the prepared nanostructures mathematically.

     

Biosynthesis of silver nanoparticle using flowers of Calotropis gigantea (L.) W.T. Aiton and activity against pathogenic bacteria

Silver nanoparticles (AgNPs) from silver nitrate solution are carried out using the flower extract of Calotropis gigantea. Silver nanoparticles were characterized by UV–vis spectrophotometer, X-Ray diffractometer (XRD). Reduction of silver ions in the aqueous solution of silver during the reaction was observed by UV–vis spectroscopy. Crystalline nature of synthesized silver nanoparticles was studied by XRD pattern, refraction peak using the Scherrer’s equation. Antibacterial activity of the silver nanoparticles was performed by disc diffusion method against Bacillus subtilis, Pseudomonas putida and Escherichia coli. The antibacterial activity of synthesized silver nanoparticles by flower extract of C. gigantea was found against B. subtilis (10 mm). Synthesised AgNPs has the efficient antibacterial activity against Gram positive bacteria.     

Morphologies and dispersion stabilities of carbon-encapsulated metal (Ag and Cu) nanoparticles synthesized by pulsed-wire evaporation (PWE)

Carbon-encapsulated Ag and Cu nanoparticles were synthesized using pulsed-wire evaporation (PWE). All as-made materials were composed of nanocapsules with a uniform particle size at and below 50 nm. The nanocapsules consisted of an outer carbon layer shaped multi-shell. The dispersion stability of the solvent depends on the measured zeta potential for the particles in water, ethanol, ethylene glycol (EG), and polyethylene glycol (PEG). In the case of Ag@C, a stable dispersion was observed in the PEG suspension only. The stable dispersions of Cu@C were observed in EG and PEG without showing any clarification or sedimentation. Flocculation by a coalescing reaction between the nanoparticles was insignificant due to carbon layers on the surfaces of the metal (Ag and Cu) particles.     

Novel antibacterial hybrid materials based on polyvinyl alcohol and mercaptopropyltriethoxysilane with embedded silver nanoparticles (PVA/AgNps/MPTES)

Hybrid materials based on polyvinyl alcohol (PVA) and mercaptopropyltriethoxysilane (MPTES) with embedded silver nanoparticles (AgNps) have been synthesized via a sol–gel method. Silver nanoparticles were obtained via thermal reduction in the presence of PVA as a stabilizer and reducing agent. The formation of silver nanoparticles within the PVA/MPTES matrix was proven by FTIR, XRD, and TEM analysis. The antibacterial activity of PVA/AgNps/MPTES materials was determined against strains belonging to Gram-positive and Gram-negative bacteria by disk diffusion and growth curve methods. The hybrid materials showed high antibacterial activity, which depends on the concentration of the silver nanoparticles.     

Use of Natural Monomer in the Synthesis of Nano- and Microparticles of Polyurethane by Suspension-Polyaddition Technique

Summary: Polyurethane nano- and microparticles were synthesized by suspension-polyaddition technique, using aqueous polymerization medium. Castor oil, a vegetable triglyceride possessing hydroxyl groups was used as natural polyol and methylene diphenyl diisocyanate (MDI) as isocyanate. The levofloxacin, an antibacterial drug was used as model drug to measure the particles encapsulation efficiency. The effect of the addition of a second polyol, the poly(ethylene glycol) (PEG), and the stirring rate on the mean diameter and morphology of particles was also investigated. The poly(ethylene glycol) has an important effect in the reduction of particles size and their porosity. On the other hand, the poly(ethylene glycol) reduced the yield of encapsulation from 70% for the formulation without PEG to 20% for formulations with PEG. FTIR analysis confirmed the polyurethane formation. Dynamic light scattering study, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to determine the nanoparticles size and shape. Spectrofluorimetric analysis was used to detect the levofloxacin.     

Synthesis of silver nanoprisms in formamide

Polygonal (mainly triangular) silver nanoprisms were prepared by reducing silver perchlorate in formamide in the presence of polyethylene glycol (PEG) at room temperature. The reduction of silver ions by formamide leads to the deposition of arrays of triangular shaped silver nanoparticles on the glass walls of the container, accompanied by evolution of CO2 gas. In the presence of poly(N-vinyl-2-pyrrolidone) (PVP) and PEG (1:1), both nanospheres and nanoprisms are formed.     

First successful design of semi-IPN hydrogel-silver nanocomposites: a facile approach for antibacterial application

Semi-IPN hydrogels in which poly(vinyl pyrrolidone) (PVP) chains were physically dispersed throughout poly(acrylamide) (PAM) gel networks were synthesized. These semi-IPN hydrogel networks can act as excellent nanoreactors for producing and stabilizing metal nanoparticles. The current methodology allows us to entrap metal nanoparticles throughout hydrogel networks via PVP chains. An optimized semi-IPN hydrogel formulation was found to produce silver nanoparticles, ca. 3-5 nm. The synthesized semi-IPN hydrogel-silver nanocomposites were fully characterized by using UV-vis, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The developed semi-IPN hydrogel-silver nanocomposite (SHSNC) was evaluated for preliminary antibacterial applications.     

Comparative evaluation of antibacterial activity of silver nanoparticles synthesized using Rhizophora apiculata and glucose

The focus of the study is to compare the antibacterial efficacy of silver nanoparticles (AgNPs) fabricated by exploiting biological (a mangrove plant, Rhizophora apiculata) and chemical means (Glucose). The synthesized nanoparticles were characterised using UV-visible absorption spectrophotometry (UV-vis), Fourier transform Infra-red Spectroscopy (FTIR) and Transmission electron microscopy (TEM). Biologically synthesized silver nanoparticles (BAgNPs) were observed at 423 nm with particle sizes of 19-42 nm. The chemically synthesized silver nanoparticles (CAgNPs) showed a maximum peak at 422 nm with particle sizes of 13-19 nm. An obvious superiority of the antibacterial potency of BAgNPs compared to the CAgNPs as denoted by the zone of inhibition (ZoI) was noted when the nanoparticles were treated against seven different Microbial Type Culture Collection (MTCC) strains. The current study therefore elucidates that the synthesized AgNPs were efficient against the bacterial strains tested.     

Polyethylene Glycol Functionalized Graphene Oxide Nanoparticles Loaded with Nigella sativa Extract: A Smart Antibacterial Therapeutic Drug Delivery System

Flaky graphene oxide (GO) nanoparticles (NPs) were synthesized using Hummer’s method and then capped with polyethylene glycol (PEG) by an esterification reaction, then loaded with Nigella sativa (N. sativa) seed extract. Aiming to investigate their potential use as a smart drug delivery system against Staphylococcus aureus and Escherichia coli, the spectral and structural characteristics of GO-PEG NPs were comprehensively analyzed by XRD, AFM, TEM, FTIR, and UV- Vis. XRD patterns revealed that GO-PEG had different crystalline structures and defects, as well as a higher interlayer spacing. AFM results showed GONPs with the main grain size of 24.41 nm, while GONPs–PEG revealed graphene oxide aggregation with the main grain size of 287.04 nm after loading N. sativa seed extract, which was verified by TEM examination. A strong OH bond appeared in FTIR spectra. Furthermore, UV- Vis absorbance peaks at (275, 284, 324, and 327) nm seemed to be correlated with GONPs, GO–PEG, N. sativa seed extract, and GO –PEG- N. sativa extract. The drug delivery system was observed to destroy the bacteria by permeating the bacterial nucleic acid and cytoplasmic membrane, resulting in the loss of cell wall integrity, nucleic acid damage, and increased cell-wall permeability.     

Synthesis and spectroscopic characterization of gold nanoparticles

Photoluminescent nanoparticles of gold with size 3, 4, 6, and 9nm are prepared by borohydride/citrate reduction in presence of polyethylene glycol (PEG)/tannic acid. The prepared nanomaterials are characterized by UV-vis spectroscopy and dynamic light scattering (DLS) technique. Intense photoluminescence (PL) is observed in nanoparticles prepared by fast reduction with borohydride in presence of PEG. A red shift of PL emission from 408 to 456nm is observed for the change of size from 4 to 6nm. Increase in PL intensity is observed for all the nanoparticles on the addition of KCl. Citrate reduced gold colloid which consists of large particles of size approximately 35nm with anisotropic shapes showing two plasmon peaks is also prepared. The anisotropy is confirmed by TEM measurement. SERS activity of this colloid is tested using glutamic acid as an adsorbate probe. Assignment of the observed bands is given.     

In situ generation of silver nanoparticles in cellulose matrix using Azadirachta indica leaf extract as a reducing agent

In the present work, silver nanoparticles (AgNPs) were in situ generated in cellulose matrix using leaf extract of Azadirachta indica as a reducing agent. The cellulose/AgNP composite films prepared were characterized by FTIR, X-ray diffraction (XRD), scanning electron microscope, and antibacterial tests. The infrared spectra indicated the association of organic materials with silver nanoparticles to serve as capping agents. Scanning electron micrographs showed that synthesized silver nanoparticles were nearly uniform and spherical in shape with diameter in the range of 61–110?nm. XRD confirmed the formation of AgNPs and Ag–O nanoparticles. The nanocomposite films showed good antibacterial activity against Escherichia coli bacteria.     

Facile Biosynthesis of Silver Nanoparticles Using <Emphasis Type="Italic">Descurainia sophia</Emphasis> and Evaluation of Their Antibacterial and Antifungal Properties

The objective of the present study was to evaluate efficiency of silver nanoparticles (Ag-NPs) biosynthesis using Descurainia sophia as a novel biological resource. The resulting synthesized Ag-NPs were characterized using UV visible spectroscopy, X-ray diffraction, transmission electron microscopy and dynamic light scattering (DLS). The UV–Vis spectra gave surface plasmon resonance at ~420 nm. TEM images revealed formation spherical shaped Ag-NPs with size ranged from to 1–35 nm. DLS confirmed uniformity of the synthesized Ag-NPs with an average size of ~30 nm. Following, the antibacterial and antifungal activities of the synthesized Ag-NPs were investigated. The concentration 25 µg/ml of the Ag-NPs showed maximum inhibitory effect on mycelium growth of Rhizoctonia solani (More than 86 % inhibition), followed by 15 µg/ml (55 % inhibition) and 10 µg/ml (63 % inhibition). The minimum inhibitory concentration and minimum bactericidal concentration of Ag-NPs against Agrobacterium tumefaciens (strain GV3850) and A, rhizogenes (strain 15843) were 4 and 8 µg/ml, respectively. The Ag-NPs were stable in vitro for 3 months without any precipitation or decrease of antifungal effects. Finally, it could be concluded that D. sophia can be used as an effective method for biosynthesis of nanoparticles, especially Ag-NPs.     

Synthesis of highly stable silver nanoparticles by photoreduction and their size fractionation by phase transfer method

In this report we demonstrate a green chemical approach for the synthesis of stable silver nanoparticles in aqueous medium using tyrosine as an efficient photoreducing agent. A narrow size distribution of silver nanoparticles can be achieved by this simple photoirradiation method without using any additional stabilizing agents or surfactants. Two different irradiation sources have been explored resulting in a different particle size distribution pattern in each case. Further, we show that starting from a polydisperse tyrosine synthesized silver nanoparticles sample, it is also possible to fractionate them into different size ranges. The size fractionation was achieved by a 2 stage phase transfer method employing different organic solvents. The nanoparticles synthesized were characterized using UV-vis spectroscopy, Transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques.