In-vivo and in-vitro biocompatibility evaluations of silver nanoparticles with antimicrobial activity

In this study, the biocompatibility and antimicrobial activity of silver nanoparticles (Ag NPs) were evaluated in vitro and in vivo. The cytotoxicity of Ag NPs (average diameter: 2-5 nm) against CHO-K1 cells was determined via WST-8 assay, and their genotoxicity was examined via Salmonella typhimurium reverse mutation assay (Ames test). The acute toxicity and intracutaneous reactivity of Ag NPs were evaluated using animal models of mice and rabbits, respectively. The antibacterial effects of Ag NPs on the Gram (-) bacterial strains of Escherichia coli ATCC 8739 and Pseudomonas aeruginosa ATCC 9027 and on the Gram (+) bacterial strains of Staphylococcus aureus ATCC 6538p and Bacillus subtilius ATCC 6633 were determined by measuring the minimum inhibitory concentrations. The Ag NPs were highly cytotoxic to the L-929 cells at over 2 ppm but were non-cytotoxic at lower than 1 ppm. Moreover, the Ag NPs at 1 ppm or lower did not show genotoxicity, acute toxicity and intracutaneous reactivity. It was also found that the Ag NPs exerted effective antimicrobial activities on both the Gram (-) and (+) bacterial strains within the range from 0.06 to 0.98 ppm for 50% MIC.     

A novel Ag/graphene composite: facile fabrication and enhanced antibacterial properties

In this work, a novel Ag/graphene composite was synthesized as a promising antibacterial agent. The high-quality graphene was prepared from the expandable graphite first and silver nanoparticles (Ag NPs) were then supported on the graphene sheets by a facile chemical reduction. TEM, SEM, and XPS characterizations show the crystalline of Ag NPs with a typical diameter of 45–50 nm are homogeneously decorated onto graphene sheets without aggregation. Furthermore, the antibacterial activity of composite is investigated using the agar well diffusion method. Results reveal the Ag/graphene composites exhibit outstanding and stable antibacterial activity against E. coli due to good dispersibility of Ag NPs and high-quality of graphene substrate.     

Biogenic synthesis of Au,Ag and Au–Ag alloy nanoparticles using Cannabis sativa leaf extract

Biogenic synthesis of gold (Au), silver (Ag) and bimetallic alloy Au–Ag nanoparticles (NPs) from aqueous solutions using Cannabis sativa as reducing and stabilising agent has been presented in this report. Formation of NPs was monitored using UV–visible spectroscopy. Morphology of the synthesised metallic and bimetallic NPs was investigated using X‐ray diffraction and scanning electron microscopy. Elemental composition and the surface chemical state of NPs were confirmed by energy dispersive X‐ray spectroscopy analysis. Fourier transform‐infrared spectroscopy was utilised to identify the possible biomolecules responsible for the reduction and stabilisation of the NPs. Biological applicability of biosynthesised NPs was tested against five bacterial strains namely Klebsiella pneumonia, Bacillus subtilis (B. subtilis), Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa (P. aeruginosa) and Leishmania major promastigotes. The results showed considerable antibacterial and anti‐leishmanial activity. The Au–Ag bimetallic NPs showed improved antibacterial activity against B. subtilis and P. aeruginosa as compared to Au and Ag alone, while maximum anti‐leishmanial activity was observed at 250 μg ml⁻¹ NP concentration. These results suggest that biosynthesised NPs can be used as potent antibiotic and anti‐leishmanial agents.Inspec keywords: silver, silver alloys, gold, gold alloys, nanoparticles, nanofabrication, reduction (chemical), ultraviolet spectra, visible spectra, X‐ray diffraction, scanning electron microscopy, X‐ray chemical analysis, Fourier transform infrared spectra, microorganisms, antibacterial activityOther keywords: biogenic synthesis, Cannabis sativa leaf extract, bimetallic alloy Au–Ag nanoparticles, aqueous solutions, reducing agent, stabilising agent, UV–visible spectroscopy, X‐ray diffraction, scanning electron microscopy, elemental composition, surface chemical state, energy dispersive X‐ray spectroscopy analysis, Fourier transform‐infrared spectroscopy, biomolecules, bacterial strains, Klebsiella pneumonia, Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Leishmania major promastigotes, antibacterial activity, anti‐leishmanial activity, Ag, Au, AuAg     

Enhanced antibacterial activity of bifunctional Fe3O4-Ag core-shell nanostructures

We describe a simple one-pot thermal decomposition method for the production of a stable colloidal suspension of narrowly dispersed superparamagnetic Fe₃O₄-Ag core-shell nanostructures. These biocompatible nanostructures are highly toxic to microorganisms. Antimicrobial activity studies were carried out on both Gram negative (Escherichia coli and Proteus vulgaris) and Gram positive (Bacillus megaterium and Staphylococcus aureus) bacterial strains. Efforts have been made to understand the underlying molecular mechanism of such antibacterial actions. The effect of the core-shell nanostructures on Gram negative strains was found to be better than that observed for silver nanoparticles. The minimum inhibitory concentration (MIC) values of these nanostructures were found to be considerably lower than those of commercially available antibiotics. We attribute this enhanced antibacterial effect of the nanostructures to their stability as a colloid in the medium, which modulates the phosphotyrosine profile of the bacterial proteins and arrests bacterial growth. We also demonstrate that these core-shell nanostructures can be removed from the medium by means of an external magnetic field which provides a mechanism to prevent uncontrolled waste disposal of these potentially hazardous nanostructures.      

Mesoporous Silica Supported Silver–Bismuth Nanoparticles as Photothermal Agents for Skin Infection Synergistic Antibacterial Therapy

The emergence of multidrug resistant bacteria has resulted in plenty of stubborn nosocomial infections and severely threatens human health. Developing novel bactericide and therapeutic strategy is urgently needed. Herein, mesoporous silica supported silver–bismuth nanoparticles (Ag‐Bi@SiO₂ NPs) are constructed for synergistic antibacterial therapy. In vitro experiments indicate that the hyperthermia originating from Bi NPs can disrupt cell integrity and accelerate the Ag ions release, further exhibiting an excellent antibacterial performance toward methicillin‐resistant Staphylococcus aureus (MRSA). Besides, under laser irradiation, Ag‐Bi@SiO₂ NPs at 100 µg mL^?1 can effectively obliterate mature MRSA biofilm and cause a 69.5% decrease in the biomass, showing a better therapeutic effect than Bi@SiO₂ NPs with laser (26.8%) or Ag‐Bi@SiO₂ NPs without laser treatment (30.8%) groups. More importantly, in vivo results confirm that ≈95.4% of bacteria in abscess are killed and the abscess ablation is accelerated using the Ag‐Bi@SiO₂ NPs antibacterial platform. Therefore, Ag‐Bi@SiO₂ NPs with photothermal‐enhanced antibacterial activity are a potential nano‐antibacterial agent for the treatment of skin infections.     

Nitrobacter sp. extract mediated biosynthesis of Ag2 O NPs with excellent antioxidant and antibacterial potential for biomedical application

In this study, extracellular extract of plant growth promoting bacterium, Nitrobacter sp. is used for the bioconversion of AgNO₃ (silver nitrate) into Ag₂ O (silver oxide nanoparticles). It is an easy, ecofriendly and single step method for Ag₂ O NPs synthesis. The bio‐synthesized nanoparticles were characterized using different techniques. UV‐Vis results showed the maximum absorbance around 450 nm. XRD result shows the particles to have faced centered cubic (fcc) crystalline nature. FTIR analysis reveals the functional groups that are involved in bioconversion such as C–N, N–H and C=O. Energy‐dispersive X‐ray spectroscopy (EDAX) spectrum confirms that the prepared nanoparticle is Ag₂ O NPs. Particle size distribution result reveals that the average particle size is around 40 nm. The synthesized Ag₂ O NPs found to be almost spherical in shape. Biosynthesized Ag₂ O NPs possess good antibacterial activity against selected Gram positive and Gram negative bacterial strains namely Salmonella typhimurium, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae when compared to standard antibiotic. In addition, Ag₂ O NPs exhibits excellent free radical scavenging activity with respect to dosage. Thus, this study is a new approach to use soil bacterial extract for the production of Ag₂ O NPs for biomedical application.Inspec keywords: nanomedicine, nanoparticles, silver compounds, antibacterial activity, ultraviolet spectra, visible spectra, X‐ray diffraction, Fourier transform infrared spectra, X‐ray chemical analysis, particle size, free radicalsOther keywords: free radical scavenging activity, Ag₂ O, AgNO₃ , Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Gram negative bacterial strains, Gram positive bacterial strains, particle size distribution, energy‐dispersive X‐ray spectroscopy spectrum, functional groups, Fourier transform infrared analysis, faced centred cubic crystalline nature, XRD, UV‐Vis results, bio‐synthesised nanoparticles, silver oxide nanoparticles, silver nitrate bioconversion, plant growth promoting bacterium, extracellular extract, biomedical application, antibacterial potential, antioxidant potential, Ag₂ O NPs, extract mediated biosynthesis, Nitrobacter sp     

Bio-mechanochemical synthesis of silver nanoparticles with antibacterial activity

By using a bio-mechanochemical approach combining mechanochemistry (ball milling) and green synthesis for the first time, silver nanoparticles (Ag NPs) with antibacterial activity were successfully synthesized. Concretely, eggshell membrane (ESM) or Origanum vulgare L. plant (ORE) and silver nitrate were used as environmentally friendly reducing agent and Ag precursor, respectively. The whole synthesis took 30?min in the former and 45?min in the latter case. The photon cross-correlation measurements have shown finer character of the product in the case of milling with Origanum. UV–Vis measurements have shown the formation of spherical NPs in both samples. TEM study has revealed that both samples are composites of nanosized silver nanoparticles homogenously dispersed within the organic matrices. It has shown that the size and size distribution of the silver nanoparticles is smaller and more uniform in the case of eggshell membrane matrix implying lower silver mobility within this matrix. The antibacterial activity was higher for the silver nanoparticles synthesized with co-milling with Origanum plant than in the case of milling with eggshell membrane.     

One-step synthesis of reduced graphite oxide–silver nanocomposite

Here, a general approach for the preparation of reduced graphite oxide (rGO)–silver nanocomposite has been investigated. Graphite oxide (GO) sheets are used as the nanoscale substrates for the formation of rGO–silver composite. GO sheets and Ag ions can be reduced at the same time, under a mild condition using l-ascorbic acid (l-AA) as reducing agent. This simple approach should find practical applications in the production of rGO–silver nanocomposite. The SEM analysis indicates that the silver particles are dispersed on graphene sheets. Raman signals of rGO in the composite are increased by the attached silver nanoparticles, displaying surface-enhanced Raman scattering activity. The degree of enhancement can be adjusted by varying the quantity of silver nanoparticles in the composite. In addition, antibacterial activity of the composite against Escherichia coli was evaluated using zone of inhibition. Composites with Ag clearly showed antibacterial activity against E. coli. While GO alone has almost no effect against this bacteria.     

Gundelia tournefortii L.: a natural source for the green synthesis of silver nanoparticles

The present study focused on the synthesis of spherical silver nanoparticles (Ag NPs) using Gundelia tournefortii L. aerial part extract. The plant extract could reduce silver ions into Ag NPs. To identify the compounds responsible for the reduction of silver ions, functional groups present in plant extract were investigated by Fourier transform infrared spectroscopy. Techniques used to characterise synthesised nanoparticles included field emission scanning electron microscopy, X‐ray diffraction and transmission electron microscopy. UV‐visible spectrophotometer showed the absorbance peak in the range of 400–450 nm. The Ag NPs showed antibacterial activities against both gram positive (Staphylococcus aureus and Bacillus Cereus) and gram negative (Salmonella typhimurium and Escherichia coli) microorganisms. The results confirmed that this protocol was simple, rapid, eco‐friendly, low‐priced and non‐toxic; therefore, it could be used as an alternative to conventional physical/chemical methods. Only 5 min were required for the conversion of silver ions into Ag NPs at room temperature, without the involvement of any hazardous chemical.Inspec keywords: nanoparticles, silver, nanofabrication, microorganisms, Fourier transform infrared spectra, transmission electron microscopy, ultraviolet spectra, visible spectraOther keywords: Ag, temperature 293 K to 298 K, chemical method, physical method, Salmonella typhimurium, Escherichia coli, gram negative microorganisms, Bacillus Cereus, Staphylococcus aureus, gram positive microorganisms, antibacterial activities, absorbance peak, UV‐visible spectrophotometer, transmission electron microscopy, X‐ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, functional groups, plant extract, Gundelia tournefortii L. aerial part extract, spherical silver nanoparticle synthesis, silver nanoparticle green synthesis, natural source     

Studies on antimicrobial and wound healing applications of gauze coated with CHX–Ag hybrid NPs

In this study, chlorhexidine (CHX)–silver (Ag) hybrid nanoparticles (NPs) coated gauze was developed, and their bactericidal effect and in vivo wound healing capacities were tested. A new method was developed to synthesise the NPs, wherein Ag nitrate mixed with sodium (Na) metaphosphate and reduced using Na borohydride. Finally, CHX digluconate was added to form the hybrid NPs. To study the antibacterial efficacy of particles, the minimal inhibition concentration and biofilm degradation capacity against Gram‐positive and Gram‐negative bacteria was studied using Escherichia coli and Staphylococcus aureus. The results indicated that the NP inhibited biofilm formation and was bactericidal as well. The gauze was doped with NPs, and its wound healing property was evaluated using mice model. Results indicated that the wound healing process was fastened by using the NPs gauze doped with NPs without the administration of antibiotics.Inspec keywords: nanomedicine, nanoparticles, wounds, silver, cellular biophysics, biomedical materials, nanofabrication, microorganisms, antibacterial activityOther keywords: NPs gauze, antimicrobial wound healing applications, hybrid NPs, chlorhexidine–silver hybrid nanoparticles, CHX, coated gauze, bactericidal effect, minimal inhibition concentration, biofilm degradation capacity, Gram‐negative bacteria, wound healing property, wound healing process, in vivo wound healing capacities, Staphylococcus aureus, Escherichia coli, antibiotics administration, Na borohydride, Ag nitrate mixing, sodium metaphosphate, CHX digluconate, NP inhibited biofilm formation, Ag     

Green synthesis of silver nanoparticles using bovine skin gelatin and its antibacterial effect on clinical bacterial isolates

Nanoparticles are being increasingly used in day‐to‐day life. Therefore, concerns have been raised regarding their interactions with the surrounding environment. This study focused on a simple green method for synthesizing silver nanoparticles (Ag‐NPs) in an autoclave at 15 psi (103 kPa) and 121°C. An aqueous solution of AgNO₃ as a precursor of Ag‐NPs and gelatin (type B) reducing and/or stabilizing (capping) agent were used. The effect of various AgNO₃ concentrations of certain gelatin concentration and various gelatin concentrations at constant AgNO₃ concentration, and autoclaving time, was studied. UV‐Vis spectra ascribed that the presence of localized surface plasmon resonance (SPR) of the synthesized Ag‐NPs. TEM images and the selected area of electron diffraction confirmed, the formation of Ag‐NPs with a diameter of approximately 5 ±0.35 nm. Furthermore, FT‐IR revealed that a gelatin polymer matrix stabilized the synthesized Ag‐NPs. The Well diffusion assay was used to test the effect of Ag‐NPs on six clinical bacterial isolates, where Gram positive bacteria were more susceptible to Ag‐NPs than Gram negative bacteria. Therefore, Ag‐NPs capped by gelatin have remarkable potential effect as an antibacterial agent, and they not only have various medical applications but can also be used in biological, pharmaceutical and industrial fields.Inspec keywords: silver, nanoparticles, nanomedicine, antibacterial activity, microorganisms, nanofabrication, skin, gelatin, ultraviolet spectra, visible spectra, surface plasmon resonance, transmission electron microscopy, electron diffraction, Fourier transform infrared spectra, polymers, biomedical materialsOther keywords: green synthesis, silver nanoparticles, bovine skin gelatin, antibacterial effect, clinical bacterial isolates, autoclave, reducing agent, stabilising agent, ultraviolet‐visible spectra, localised surface plasmon resonance, transmissions electron microscope images, electron diffraction, Fourier transform infrared spectroscopy, gelatin polymer matrix, well diffusion assay, gram negative bacteria, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, gram positive bacteria, Bacillus megaterium, Streptococcus pyogenes, Staphylococcus aureus, temperature 121 degC, Ag     

Comparison of antibacterial activity of Ag nanoparticles synthesized from leaf extract of Parthenium hystrophorus L in aqueous media and Gentamicin sulphate: in-vitro

Monodisperse silver (Ag) nanoparticles were synthesized by using Parthenium hystrophorus L leaf extract in aqueous media. The synthesized nanoparticles were characterized by using UV-vis spectrophotometer, X-ray diffracto-meter (XRD), transmission electron microscope (TEM), and dynamics light scattering (DLS). Size-dependent antibacterial activities of Ag nanoparticles were tested against Gram negative Pseudomonas aeruginosa and Gram positive Staphylococcus aureus. Ag nanoparticles having 20?±?2?nm size in diameter show maximum zone of inhibition (23?±?2.2?mm) in comparison to 40?nm and 70?nm diameter nanoparticles for Pseudomonas aeruginosa. The zone of inhibition against Staphylococcus aureus were 19?±?1.8?mm, 15?±?1.5?mm and 11?±?1?mm for 20?nm, 40?nm, and 70?nm, respectively. In addition, affect of concentration of 20?nm size Ag nanoparticles on Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus species were also reported and results were compared with 10?µg/ml dose of Gentamicin sulphate. The Parthenium hystrophorus L leaf extract capped 20?±?2?nm Ag nanoparticles (7.5?µg/ml) shows statistically significant antibacterial activity than Gentamicin sulphate (10?µg/ml) against Staphylococcus aureus.     

Gold nanorods core/AgPt alloy nanodots shell: A novel potent antibacterial nanostructure

In the light of the current problems of silver nanoparticles （Ag NPs） in terms of antibacterial performance, we have designed a novel trimetallic corelshell nanostructure with AgPt alloy nanodots epitaxially grown on gold nanorods （Au@PtAg NRs） as a potential antibacterial agent. Both Escherichia coli （E. coli） and Staphylococcus aureus （S. aureus） were studied. The antibacterial activity exhibits an obvious composition-dependence. On increasing the Ag fraction in the alloy shell up to 80%, the antibacterial activity gradually increases, demonstrating a flexible way to tune this activity. At 80% Ag, tile antibacterial activity is better than that of a pure Ag shell. The improved antibacterial ability mainly results from the high exposure of silver on the shell surface due to the dot morphology. We thus demonstrate that forming alloys is an effective way to improve antibacterial activity while retaining high chemical stability for Ag-based nanomaterials. Furthermore, due to the tunable localized surface plasmonic response in the near-infrared （NIR） spectral region, additional control over antibacterial activity using light--such as photothermal killing and photo- triggered silver ion release--is expected. As a demonstration, highly enhanced antibacterial activity is shown by utilizing the NIR photothermal effect of the nanostructures. Our results indicate that such tailored nanostructures will find a role in the future fight against bacteria, including the challenge of the increasing severity of multidrug resistance.     

Extracellular biosynthesis,characterisation and in-vitro antibacterial potential of silver nanoparticles using Agaricus bisporus

Microbial silver nanoparticles have been known to have bactericidal effects but the antimicrobial mechanism has not been clearly revealed. The use of microorganisms in the synthesis of nanoparticles emerges as an ecofriendly and exciting approach. Here we report on the extracellular synthesis method for the preparation of silver nanoparticles in water using the extract of Agaricus bisporus, a naturally occurring edible mushroom, as reducing and protecting agents. The silver nanoparticles were characterised by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) analysis. The synthesised silver nanoparticles showed antibacterial activity against the multi-drug resistant Gram positive and Gram negative bacterial pathogens.     

Facile synthesis of silver nanoparticles mediated by polyacrylamide‐reduction approach to antibacterial application

The current time increase in the prevalence of antibiotic resistant ‘super‐bugs’ and the risks associated with food safety have become global issues. Therefore, further research is warranted to identify new and effective antimicrobial substances. Silver nanoparticles (Ag‐NPs) were synthesized by autoclaving technique using, different concentrations of Ag salt (AgNO₃) solution (1, 5, 10, and 25 mM). Their presence was confirmed by a surface plasmon resonance band at ∼435 nm using UV–Vis absorption spectra. The morphology of the synthesized Ag‐NPs stabilized by polyacrylamide (PAM) was examined by TEM, SAED, and EDS. TEM images revealed that the synthesized Ag‐NPs had an average diameter of 2.98±0.08 nm and SAED and EDS results confirmed the formation of Ag‐NPs. In addition, FT‐IR spectroscopy revealed that a PAM polymer matrix stabilized the Ag‐NPs. The well diffusion method, was used to test, Gram positive and Gram negative bacteria were examined. Also the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were studied against Ag‐NPs. The Ag‐NPs exhibited strong inhibitory activity, MIC and MBC against the tested clinical bacterial isolates. These results suggest that Ag‐NPs stabilized in PAM are highly effective against clinical bacterial isolates can be applied in medical fields.Inspec keywords: antibacterial activity, silver, nanoparticles, nanomedicine, surface plasmon resonance, X‐ray chemical analysis, transmission electron microscopy, electron diffraction, Fourier transform infrared spectroscopy, microorganisms, ultraviolet spectra, visible spectraOther keywords: Ag‐NP facile synthesis, PAM‐reduction approach, antibacterial application, antibiotic resistant super‐bugs, food safety, antimicrobial agents, antibiotics, antimicrobial substances, Ag salt solution concentration, ultraviolet‐visible absorption spectra, polyacrylamide, transmission electron microscopy, electron diffraction, energy dispersive X‐ray spectroscopy, TEM images, Fourier transform infrared spectroscopy, PAM polymer matrix, diffusion method, Gram positive bacteria, Gram negative bacteria, clinical bacterial isolates, Ag     

Eradication of Multi‐Drug Resistant Bacteria by a Novel Zn‐doped CuO Nanocomposite

Zinc‐doped copper oxide nanoparticles are synthesized and simultaneously deposited on cotton fabric using ultrasound irradiation. The optimization of the processing conditions, the specific reagent ratio, and the precursor concentration results in the formation of uniform nanoparticles with an average size of ≈30 nm. The antibacterial activity of the Zn‐doped CuO Cu_0.88Zn_0.12O in a colloidal suspension or deposited on the fabric is tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) bacteria. A substantial enhancement of 10 000 times in the antimicrobial activity of the Zn–CuO nanocomposite compared to the pure CuO and ZnO nanoparticles (NPs) is observed after 10 min exposure to the bacteria. Similar activities are observed against multidrug‐resistant bacteria (MDR), (i.e., Methicillin‐resistant S. aureus and MDR E. coli) further emphasizing the efficacy of this composite. Finally, the mechanism for this enhanced antibacterial activity is presented.     

Synthesis of Starch-Stabilized Silver Nanoparticles and Their Antimicrobial Activity

In this study, silver nanoparticles were prepared using silver nitrate as the metal precursor, starch as protecting agent, and sodium borohydride (NaBH₄) as a reducing agent by the chemical reduction method. The formation of the silver nanoparticles was monitored using ultraviolet-visible absorption spectroscopy, cyclic voltammetry, and particle size analyzer and characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD). Synthesis of nanoparticles were carried out by varying different parameters, such as reaction temperature, concentration of reducing agent, concentration of silver ion in feed solution, type and concentration of the stabilizing agent, and stirrer speed expressed in terms of particle size and size distribution. Dispersion destabilization of colloidal nanoparticles was detected by Turbiscan. It was observed that size of the starch stabilized silver nanoparticles were lower than 10 nm. The microbial activity of synthesized silver nanoparticles was examined by modified Kirby-Bauer disk diffusion method. Silver nanoparticles were tested for their antibacterial activity against Gram negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Gram positive bacteria such as Staphylococcus aureus and Staphylococcus epidermidis. High bacterial activity was observed at very low concentrations of silver (below 1.39 μg/ml). The antifungal activity of silver nanoparticles has been assayed against Candida albicans.     

Synthesis of oleic acid-stabilized silver nanoparticles and analysis of their antibacterial activity

The development of new and simple green chemical methods for synthesizing colloidal solutions of functional nanoparticles is desirable for environment-friendly applications. In the present work, we report a feasible method for synthesizing colloidal solutions of silver nanoparticles (Ag NPs) based on the modified Tollens technique. The Ag NPs were stabilized by using oleic acid as a surfactant and were produced for the first time by the reduction of silver ammonium complex [Ag(NH₃)₂]⁺_(aq) by glucose with UV irradiation treatment. A stable and nearly monodisperse aqueous Ag NPs solution with average-sized particles (~ 9–10 nm) was obtained. The Ag NPs exhibited high antibacterial activity against both Gram-negative Escherichia Coli (E. coli) and Gram-positive Staphylococcus aureus bacteria. Electron microscopic images and analyses provided further insights into the interaction and bactericidal mechanism of the Ag NPs. The proposed method of synthesis is an effective way to produce highly bactericidal colloidal solutions for medical, microbiological, and industrial applications.     

The fabrication of the antibacterial paste based on TiO2 nanotubes and Ag nanoparticles-loaded TiO2 nanotubes powders

ABSTRACT

We successfully synthesised TiO₂ nanotubes (TNTs) and silver nanoparticles (Ag NPs)-loaded TiO₂ nanotubes paste. These were coated on a glass substrate by spin coating method, and their antibacterial activities were surveyed. The morphology of materials was defined by transmission electron microscopy (TEM) image; the crystalline structure and the composition of the materials were determined by X-ray diffraction (XRD) pattern and X-ray photoelectron spectroscopy (XPS). Vibrational properties of the molecules existing in the sample were investigated by Fourier transform infrared (FTIR) spectroscopy, and the transmittances of films were determined by UV–Vis transmittance spectroscopy. This research shows that the structure and morphology of TNTs did not change after they underwent the processes of paste preparing and film coating on a glass substrate. Furthermore, the transmittance of TNTs film (about 75%) is higher than Ag NPs-loaded TiO₂ nanotubes (Ag/TNTs) film (about 65%) in the visible region. Moreover, the antibacterial property of Ag/TNTs film shows its effectiveness against Escherichia coli bacteria, and the antibacterial efficiency is 99.06% for 24 h-incubation period in the dark condition.     

Copper nanoparticles catalysed an efficient one-pot multicomponents synthesis of chromenes derivatives and its antibacterial activity

In this study, copper nanoparticles (Cu NPs) were synthesised by using diethylenetriamine as a protective agent in chemical reduction method. The obtained nanoparticles were characterised by various spectroscopic techniques like powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR), UV–visible spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermal analysis (TG/DTA). The structure and composition were estimated by PXRD, FTIR, EDS, UV–visible and TG/DTA techniques, while particles size and morphology behaviours were investigated by SEM and TEM instrumentation. A noteworthy, average particle size of nanoparticles was found around 40 nm with spherical shapes. Furthermore, the applications part of NPs were studied as a catalyst for one-pot solvent-free green synthesis of 3,4-dihydropyrano[c]chromenes from different aromatic aldehydes, malonitrile and 4-hydroxycoumarin by stirring at 80 °C. Moreover, the antibacterial properties of NPs were assessed in vitro against human bacterial pathogen such as Staphylococcus aureus, Escherichia coli, Klebsiella sp. and Pseudomonas aruginosa using agar well diffusion method. Gram positive bacteria S. aureus (18 mm) exhibited a maximum zone of inhibition at 60 µg/ml of Cu NPs. Nonetheless, antibacterial activities of Cu NPs (10–100 µg) were compared with four well-known antibiotics likes amikacin (30 mcg), ciprofloxacin (5 mcg), gentamicin (5 mcg) and norfloxacin (10 mcg). This study indicates that Cu NPs exhibited a strong antibacterial activity against all the test pathogens even at lower concentration.