Antibacterial Effect Of Silver Nanoparticles Research Articles

Antibacterial efficacy of silver nanoparticles, sodium hypochlorite, chlorhexidine, and hypochlorous acid on dentinal surfaces infected with Enterococcus faecalis.

The purpose of this study was to evaluate the antibacterial effect of silver nanoparticles (AgNPs) against Enterococcus faecalis and compare it with different irrigation solutions. This study was performed using 64 dentin blocks. E. faecalis suspension was dispensed to each sample and incubated under anaerobic conditions at 37°C throughout 21 days. After the inoculation period, the following solutions were added to each group and kept for 5 min: Group 1, 5.25% sodium hypochlorite (NaOCl); Group 2, 2.5% NaOCl; Group 3, 1% NaOCl; Group 4, 2% chlorhexidine (CHX); Group 5, 200 ppm hypochlorous acid (HOCl); and Group 6, AgNPs. The samples of positive control were treated with sterile saline. Biofilm viability assay was performed using the LIVE/DEAD BacLight Bacterial Viability Kit. Samples were examined using confocal laser scanning microscopy, respectively. There was no significant difference between the 5.25% NaOCl, 2.5% NaOCl, and 1%NaOCl groups (p > .05). However, these groups showed statistically higher antibacterial activity than the 2% CHX, 200 ppm HOCl, and AgNP groups. Also, 2% CHX showed greater percentage of dead cells compared with the AgNP and HOCl groups. While AgNPs group showed lower dead cell rate than all NaOCl groups and 2% CHX, it caused higher dead cells than 200 ppm HOCl group. The 200 ppm HOCl group showed the lowest percentage of dead cells (p < .05) Although the antibacterial effect of AgNPs is not as high as NaOCl and CHX, it has considerable bactericidal activity against E. faecalis and can be improved by further studies. RESEARCH HIGHLIGHTS: New antimicrobial approaches for root canal irrigation. Antimicrobial effect of silver nanoparticles against E. faecalis. Elimination of the biofilm layer for the success of endodontic treatment.

Tailoring Mesoporous Silica-Coated Silver Nanoparticles and Polyurethane-Doped Films for Enhanced Antimicrobial Applications.

The global increase in multidrug-resistant bacteria poses a challenge to public health and requires the development of new antibacterial materials. In this study, we examined the bactericidal properties of mesoporous silica-coated silver nanoparticles, varying the core sizes (ca. 28 nm and 51 nm). We also investigated gold nanoparticles (ca. 26 nm) coated with mesoporous silica as possible inert metal cores. To investigate the modification of antimicrobial activity after the surface charge change, we used silver nanoparticles with a silver core of 28 nm coated with a mesoporous shell (ca. 16 nm) and functionalized with a terminal amine group. Furthermore, we developed a facile method to create mesoporous silica-coated silver nanoparticles (Ag@mSiO2) doped films using polyurethane (IROGRAN®) as a polymer matrix via solution casting. The antibacterial effects of silver nanoparticles with different core sizes were analyzed against Gram-negative and Gram-positive bacteria relevant to the healthcare and food industry. The results demonstrated that gold nanoparticles were inert, while silver nanoparticles exhibited antibacterial effects against Gram-negative (Escherichia coli and Salmonella enterica subsp. enterica serovar Choleraesuis) and Gram-positive (Bacillus cereus) strains. In particular, the larger Ag@mSiO2 nanoparticles showed a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of 18 µg/mL in the Salmonella strain. Furthermore, upon terminal amine functionalization, reversing the surface charge to positive values, there was a significant increase in the antibacterial activity of the NPs compared to their negative counterparts. Finally, the antimicrobial properties of the nanoparticle-doped polyurethane films revealed a substantial improvement in antibacterial efficacy. This study provides valuable information on the potential of mesoporous silica-coated silver nanoparticles and their applications in fighting multidrug-resistant bacteria, especially in the healthcare and food industries.

The Antimicrobial Activity of Propolis Ethanolic Extract and Silver Nanoparticles Synthesized by Green Method on Gram-Positive and Negative Bacteria

Background: The increasing resistance of bacteria to different classes of antibiotics has become an important public health concern. This study was aimed at the effectiveness of the antibacterial effect of silver nanoparticles and propolis (AgNPs@propolis) on bacteria. Methods: A hydroalcoholic extract of propolis was used for prepare of silver nanoparticles (AgNPs@propolis). The characteristics, anti-bacterial effect and cell toxicity of AgNPs@propolis were examined in vitro. Results: The size of the synthesized nanoparticles was 32 to 85 nm. The AgNPs@propolis had no toxic effect up to a concentration of 200 μg/mL. Compared to AgNPs and propolis, AgNPs@ propolis showed a greater inhibitory effect on the growth of gram-positive and gram-negative bacteria. propolis as a natural substance has an inhibitory effect on the growth of bacteria. Conclusion: Green synthesis of AgNPs@propolis has a low toxic effect on the cell and has a high effect in inhibiting the growth of various bacteria.

Antibacterial Effect of Silver Nanoparticles Synthesized from the Secondary Metabolites of Marine Actinomycete Species

Bioprospecting marine actinomycetes can yield biological solutions to many of the key human concerns. The primary reservoir of bioactive metabolites with diverse applications is found in marine actinomycetes. Bioactive secondary metabolites produced by marine actinomycetes are widely used as immunosuppressives, antimicrobials, enzymes, and cosmetics. Actinoplanes, Micromonospora, Saccharopolyspora, Streptomyces, and Amycolatopsis are the main taxonomic groups of actinomycete that are important to industry. Because of the effectiveness of actinomycetes and their bioactive secondary metabolites, modern research is concentrating more on marine actinobacteria to address current difficulties. Nanotechnology combines the concepts of physics, chemistry, and biology to produce particles smaller than 100 nm, or nanoparticles, with specific applications. When it comes to a diverse array of bacteria and fungus, silver nanoparticles have broad spectrum antibacterial characteristics. Within the medical community, silver nanoparticles have become more well-liked because of their antibacterial properties.

Preparation and characterization of ι-carrageenan nanocomposite hydrogels with dual anti-HPV and anti-bacterial activities

Sexually transmitted diseases (STDs) are usually caused by co-infections of bacteria and viruses. However, there is a lack of products that possess both antibacterial and antiviral activities without using chemical drugs. Here, we developed a carrageenan silver nanoparticle composite hydrogel (IC-AgNPs-Gel) based on the antiviral activity of iota carrageenan (IC) and the antibacterial effect of silver nanoparticles (AgNPs) to prevent STDs. IC-AgNPs-Gel showed excellent biocompatibility, hemostasis, antibacterial and antiviral effects. IC-AgNPs-Gel not only effectively prevented S. aureus, E. coli, P. aeruginosa, and C. albicans without using antibiotics, but also significantly inhibited human papilloma virus (HPV)-16 and HPV-6 without using chemotherapy drugs. Moreover, IC-AgNPs-Gel showed the effects of accelerating infected wound healing and reducing inflammation in a rat wound model infected with S. aureus. Therefore, the multifunctional hydrogel shows great potential application prospect in preventing STDs.

Antibacterial Effect of Silver Nanoparticles Biosynthesized Using Aspergillus niger on E.coli Isolated From Chicken

Antibacterial Effect of Silver Nanoparticles Biosynthesized Using Aspergillus niger on E.coli Isolated From Chicken

The effect of surface-modified silver nanoparticles on the inflammatory component of the intragingival peri-implant area

Aim: to evaluate the intensity of the gingival inflammatory component in the peri-implant area by studying the mucous membrane bleeding in the implant area according to the papilla bleeding index (PBI), when using healing abutments with a surface modified with silver nanoparticles (AgNP). Materials and methods. 40 patients undergoing rehabilitation for secondary partial adentia by the method of dental implantation were enrolled in the study and divided into 2 groups: Group 1 (20 patients) – healing abutments with the surface modified by the method of plasma electrooxidation and AgNP-doped were fixed; Group 2 (20 patients) – standard healing abutments of the implant system used with a polished surface were fixed. The control group (20 patients) – to determine reference values. A total of 60 patients were involved in the study. The degree of bleeding was measured according to the PBI. The mucous membrane thickness was assessed using an endodontic reamer. Results. There was no statistically significant difference in bleeding level 0 between Groups 1 and 2, but the study group was significantly different from the control group (p &lt; 0.001). According to the bleeding level 3, there was a statistically significant difference between Groups 1 and 2, the study group was (12.7 %) versus 48.5 % (p &lt; 0.001). In addition, the study group was significantly different from the control group (p = 0.019), but this was due to the fact that the measurements were taken directly from the wound surface and the comparison was made to understand inflammatory manifestations as a whole. According to bleeding level 4, there were no patients with this level in the study group, but in the comparison group there were 19.2 % of those (p &lt; 0.001). Based on the results of the data obtained, it is advisable to consider effective use of the antibacterial effect of silver nanoparticles to reduce the gingival inflammatory component in the peri-implant area. Conclusions. The use of the bleeding index (PBI) is appropriate in the clinical diagnosis of inflammatory processes in the peri-implant area. Reduction of levels 3, 4 bleeding in the peri-implant area by 35.8 % and 19.2 %, respectively, in patients using healing abutments coated with AgNP compared to polished ones, indicates a pronounced anti-inflammatory effect of the proposed AgNP-doped surface. The absence of a statistical difference in the mucous membrane thickness of the studied areas between the groups allows us to consider the obtained results as consequences of the silver nanoparticle impact with an antibacterial effect. The result of this study allows recommending the proposed AgNP-doped surface for use in clinical practice.

Antibacterial effect of silver nanoparticles synthesized by green method using diospyros extract against the orodental bacteria

Antibacterial effect of silver nanoparticles synthesized by green method using diospyros extract against the orodental bacteria

Construction of silver-coated high translucent zirconia implanting abutment material and its property of antibacterial

High translucent zirconia (HTZ) has excellent mechanical properties, biocompatibility, and good semi-translucency making it an ideal material for aesthetic anterior dental implant abutments without antibacterial properties. In the oral environment, the surface of the abutment material is susceptible to microbial adhesion and biofilm formation, which can lead to infection or peri-implantitis and even implant failure. This study aims to promote the formation of a biological seal at the implant-soft tissue interface by modifying the HTZ surface, using the load-bearing capacity of the aluminosilicate porous structure and the broad-spectrum antibacterial effect of silver nanoparticles to prevent peri-implant bacterial infection and inflammation and to improve the success rate and prolong the use of the implant. FE-SEM (field emission scanning electron microscopes), EDS (energy dispersive spectroscopy), and XPS (X-ray photoelectron spectroscopy) results showed that aluminosilicate non-vacuum sintering can form open micro- and nanoporous structures on HTZ surfaces, and that porous aluminosilicate coatings obtain a larger number, smaller size, and more uniformly shaped silver nanoparticles than smooth aluminosilicate coatings, and could be deposited deeper in the coating. The ICP-AES (inductively coupled plasma-atomic emission spectroscopy) results showed that the early silver ion release of both the smooth silver coating and the porous silver coating was obvious, the silver ion concentration released by the former was higher than that of the latter. However, the silver ion concentration released by the porous silver coating was higher than that of the smooth coating when the release slowed down. Both smooth and porous silver coatings both inhibited E. coli (Escherichia coli), S. aureus (Staphylococcus aureus), and L. acidophilus (L. acidophilus), and porous silver coatings had stronger antibacterial properties. The silver coating was successfully constructed on the surface of HTZ, through aluminium silicate sintering and silver nitrate solution impregnation. It was found that the high concentration environment of silver nitrate solution was more advantageous for nano-Ag deposition, and the non-vacuum sintered porous surface was able to obtain a larger number of nano-Ag particles with smaller sizes. The porous Ag coating exhibited superior antibacterial properties. It was suggested that the HTZ with silver coating had clinical application, and good antibacterial properties that can improve the survival rate and service life of implants.

Antimicrobial Effect of Silver Nanoparticles and Combination with Cotrimoxazole against Salmonella Typhi in Vitro and in Animal Model

Introduction: Salmonella typhi is a large group of gram-negative bacilli with Enterobacteriaceae and common pathogens between humans and animals, which is the main cause of typhoid fever in humans. One of the most common antibiotics in the treatment of Salmonella is cotrimoxazole, but due to the widespread use of antibiotics, bacterial resistance has developed. The aim of this study was to investigate the antibacterial effect of silver nanoparticles and its combination with the antibiotic cotrimoxazole to produce a more effective antimicrobial drug against Salmonell typhi.&#x0D; Methods: In this experimental study, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for silver nanoparticles and combination with cotrimoxazole, was performed based on microdilution method. Then, their antibacterial effects were investigated in infected mouse model. In order to analyze the results statistically, SPSS software version 16 was used. In this test, P&lt; 0.05 was considered as a significant level.&#x0D; Results: MIC and MFC of silver nanoparticles for Salmonella typhi were 4 ppm and 8 ppm respectively, composition of silver nanoparticles with cotrimoxazole for Salmonella typhi were 62 ppm and 125 ppm and cotrimoxazole for Salmonella typhi were 500 ppm and 1000 ppm. Mouse model to study the antibacterial effect of silver nanoparticles and combination with cotrimoxazole against Salmonella typhi infection was confirmed., Silver nanoparticles had the highest antibacterial effect and cotrimoxazole has the lowest antibacterial effect than other groups.&#x0D; Conclusion: Silver nanoparticles are very effective compared to other groups, especially the antibacterial cotrimoxazole.

Comparison of the Antibacterial Effect of Silver Nanoparticles and a Multifunctional Antimicrobial Peptide on Titanium Surface.

Titanium implantation success may be compromised by Staphylococcus aureus surface colonization and posterior infection. To avoid this issue, different strategies have been investigated to promote an antibacterial character to titanium. In this work, two antibacterial agents (silver nanoparticles and a multifunctional antimicrobial peptide) were used to coat titanium surfaces. The modulation of the nanoparticle (≈32.1 ± 9.4 nm) density on titanium could be optimized, and a sequential functionalization with both agents was achieved through a two-step functionalization method by means of surface silanization. The antibacterial character of the coating agents was assessed individually as well as combined. The results have shown that a reduction in bacteria after 4 h of incubation can be achieved on all the coated surfaces. After 24 h of incubation, however, the individual antimicrobial peptide coating was more effective than the silver nanoparticles or their combination against Staphylococcus aureus. All tested coatings were non-cytotoxic for eukaryotic cells.

Effective treatment of Staphylococcus aureus infection with silver nanoparticles and silver ions

Wound healing from bacterial infections is often challenging, especially in patients with chronic disease and severe burns. Owing to the abuse of antibiotics, resistant bacteria emerge and make the treatment of infected wounds more difficult. Treatment of bacterially infected wounds with inorganic antimicrobials may address bacterial resistance. This study explored the antibacterial effects of silver nanoparticles (AgNPs) and Ag+ in vitro, and their therapeutic effects on staphylococcus aureus (S. aureus) infected wounds in vivo. By measuring the minimum inhibitory concentration, inhibition zone and anti-biofilm effect, it was found that AgNPs and Ag + have excellent antibacterial effects on S. aureus and methicillin-resistant staphylococcus aureus (MRSA), and Ag + showed better antibacterial effects than AgNPs in vitro. Besides, it is found that both AgNPs and Ag+ can promote wound healing, but the antibacterial effect of AgNPs is better than that of Ag+ in vivo. In conclusion, AgNPs can be used as a potential antibacterial agent for the treatment of wound infections, and the results of this study can provide a theoretical basis for the application of AgNPs-containing preparations and their derivatives (AgNPs dressings or AgNPs gels, etc.) in the medical field.

Antibacterial Effect of Eco-Friendly Silver Nanoparticles and Traditional Techniques on Aged Heritage Textile, Investigated by Dark-Field Microscopy

An improper indoor microclimate has adverse effects on the state of preservation of historical textiles arranged in them, favoring the development of bacteriological microflora. The current study aims to combine traditional and innovative methods for cleaning and preserving a 100-year-old traditional blouse from Bihor, Romania. The material of the blouse was impregnated with 30 and 70 ppm silver nanosuspensions and washed with a substance obtained from boiling natural wood ash (lye). The research goals were to determine the antimicrobial action of lye washing and silver nanoparticles applied to the analyzed textile material and identify the way in which the environmental factors (light) act upon the conservation degree of textile objects impregnated with silver nanoparticles. All these procedures are eco-friendly and do not cause any damage to the constituent material of the fabrics. The use of the hyperspectral imaging technique proved the permeation of both 30 and 70 ppm silver nanosuspensions into the textile, producing changes in the textile’s reflectance spectrum after being treated with them. The results showed anti-bactericidal/fungal properties of both silver nanoparticles and lye. Microbiological analyses revealed that bacterial colonies were reduced to more than 95% in both cases. The antibacterial effect of silver nanoparticles on the textile material of the blouse was maintained throughout the duration of the study, and under normal environmental conditions, the effects would remain active for a long period.

Influence of Polyvinylpyrrolidone Concentration on Properties and Anti-Bacterial Activity of Green Synthesized Silver Nanoparticles.

Environmentally green synthesis of stable polyvinyl pyrrolidone (PVP)-capped silver nanoparticles (PVP-AgNPs) was successfully carried out. The present study focused on investigating the influence of adding PVP during the synthesis process on the size, optical properties and antibacterial effect of silver nanoparticles produced. An aqueous extract of Eucalyptus camaldulensis leaves was used as a reducing agent. The effects of different PVP concentrations and reducing time on the synthesis of nanoparticles (NPs) were characterized by UV–Vis spectrophotometry, scanning electron microscopy (SEM), energy dispersive spectrum (EDX), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and nano tracker analysis (NTA). The addition of PVP was studied. The prepared PVP-AgNPs were spherical with an average size of 13 nm. FTIR analysis confirmed that PVP protects AgNPs by a coordination bond between silver nanoparticles and both N and O of PVP. DLS results indicated the good dispersion of silver nanoparticles. PVP-AgNPs were found to be stable for nearly 5 months. Antibacterial studies through the agar well diffusion method confirmed that silver nanoparticles synthesized using PVP had no inhibitor activity toward Gram-positive and Gram-negative bacteria as opposed to silver nanoparticles prepared without adding PVP, which showed a significant antibacterial activity towards some of the tested pathogens.

Synthesis of silver nanoparticles with high efficiency and stability by culture supernatant of Bacillus ROM6 isolated from Zarshouran gold mine and evaluating its antibacterial effects

BackgroundThe use of bacteria to synthesize nanoparticles as an environment-friendly method has recently been considered by researchers. Bacteria residing in different mines have shown high potential in the synthesis of metal nanoparticles due to their compatibility with the environment. The aim of this study was to evaluate the ability of Zarshouran gold mine bacteria to synthesize silver nanoparticles and their antibacterial activity.MethodsAfter isolation of mine bacteria and several screening steps, silver ion tolerant bacteria that were able to synthesize extracellular silver nanoparticles were isolated and the most suitable isolate was selected and sequenced. The characteristics, stability, and production efficiency of silver nanoparticles were evaluated using UV–vis spectrophotometry, DLS, TEM, FTIR, and X-ray diffraction analysis. Finally, the antibacterial effect of silver nanoparticles against pathogenic bacteria was investigated.ResultsAmong the eight silver-tolerant bacteria, isolate No. 6 had high antibacterial activity and high potential in the synthesis and stabilization of silver nanoparticles. Therefore, this isolate was selected for the next experiments. The results of 16S rDNA sequencing showed that this isolate is related to Bacillus pumilus. We registered in the NCBI Bank called ROM6 with access number MW440543. The DLS and TEM analysis showed that silver nanoparticles produced by this isolate were most spherical with a size of less than 25 nm and were stable for at least 180 days. The efficiency at concentrations less than 0.9 g/l silver nitrate was over 90% and the minimum inhibition concentration of nanoparticles was determined against S. aureus, E. coli, P. aeruginosa, and A. baumannii ranging from 1.4 to 5.6 µg/ml.ConclusionWe found that the bacteria residing in the gold mine have a high capacity for the synthesis of spherical and high stable silver nanoparticles with a strong antibacterial effect.

Antibacterial Effect of Silver Nanoparticles Is Stronger If the Production Host and the Targeted Pathogen Are Closely Related.

Microbial resistance to antibiotics is one of the key challenges that lead to the search for alternate antimicrobial treatment approaches. Silver nanoparticles (AgNPs) are well known for their antimicrobial effects against a wide variety of drug-resistant microorganisms. AgNPs can be synthesized using microbial hosts, using a green and economical synthesis route, which produces extremely stable and highly active nanoparticles. Such green AgNPs are coated with a biological coating often referred to as a corona, originating from the production microorganism. In this study, we asked whether the composition of the biological corona might influence the antimicrobial activity of green AgNPs. To investigate this, we produced AgNPs in Pseudomonas putida KT2440 and Escherichia coli K12 MG1655, and tested them against pathogen species from the corresponding genera. AgNPs exhibited a size range of 15–40 nm for P. putida and 30–70 nm for E. coli, and both types of nanoparticles were surrounded by a thick biological corona layer, providing extreme stability. The nanoparticles remained stable over long periods and exhibited negative zeta potential values. P-AgNPs (obtained from P. putida) were tested against pathogenic Pseudomonas aeruginosa PAO1, and E-AgNPs (obtained from E. coli) were tested against pathogenic Escherichia coli UTI 89. Antimicrobial studies were conducted by Minimum bactericidal concentration (MBC), live/dead staining and SEM analysis. MBC of P-AgNPs against P. aeruginosa was 1 μg/mL, and MBC of E-AgNPs against E. coli UTI 89 was 8 μg/mL. In both cases, the MBC values were superior to those of green AgNPs produced in organisms unrelated to the target pathogens, available in the literature. Our results suggest that NPs produced in microorganisms closely related to the target pathogen may be more effective, indicating that the composition of the biological corona may play a crucial role in the antimicrobial mechanism of AgNPs.

Evaluation of antibacterial effect of silver nanoparticles paste with and without curcumin as intracanal medication

BackgroundThe purpose of the current study was to compare the antibacterial activity of silver nanoparticles AgNPs paste and silver nanoparticles AgNPs with curcumin paste as intracanal medications versus calcium hydroxide Ca(OH)2 paste. Thirty extracted, human teeth with single roots were decoronated and mechanically prepared. After sterilization, roots were inoculated with Enterococcus faecalis for 10 days. Roots were separated into three groups in accordance to kind of intracanal medications used; Group A, silver nanoparticles AgNPs (Nanogate company, Cairo, Egypt). Group B, silver nanoparticles AgNPs with curcumin (Nanogate company, Cairo, Egypt). Group C, calcium hydroxide Ca(OH)2 (Metapaste, META BIOMED). First microbiological samples (S1) were collected from the canal, before insertion of intracanal medication. Intracanal medications were kept in root canals in all groups for 7 days; then second microbiological samples (S2) were collected from the canals after medicament removal. After the colony forming units CFUs have been counted, the data were statistically analyzed.ResultsIn the three tested groups, the highest bacterial count was found in (S1), while the least bacterial count was found in (S2) with statistical significant difference between them.ConclusionsThe effect of AgNPs paste and AgNPs with curcumin paste was superior to Ca(OH)2 paste. AgNPs with curcumin paste had the best antibacterial effect.

Antibacterial Effect of Silver Nanoparticles Dispersed over Graphene Silicate on Gram-Positive and Gram-Negative Bacteria

Due to the widespread prescription of antibiotics has caused the surge of antibiotic resistant bacterial strains and reduced the effectiveness of treatment methods. The application of nanotechnology in medicine has introduced new pathways for medical treatments and therapy. For example, many researchers has shown the potential of nanoparticles in medical imaging, drug delivery, and treatment of life-threatening diseases. Among the nanotechnology, nanoparticles are increasingly used to target bacteria. Among the nanoparticles, silver nanoparticles have been applied in antimicrobial technologies due to their high surface area. However, some studies showed that bacteria can develop resistance to silver nanoparticles after repeated exposure. In order to improve the stability of nanoparticles, it is necessary to support nanoparticles with capping agents or templates. In our research, the silver nanoparticles was supported over graphene silicate (Ag-Gsi). Many carbon materials such as activated carbon and graphene material are well-known for their antibacterial effect and stability. The use of silicate template is for further enhancing the adhesion and dispersion of silver nanoparticle on the surface of graphene material. The structure of nanocomposite was determine by using Powder X-Ray Diffraction (P-XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and Fourier Transform Infrared (FTIR). The antimicrobial test and zone inhibition test were applied to examine the effect of the composite against Escherichia coli and Bacillus subtilis. The research showed that the antibacterial ability of Ag-Gsi was higher than that of graphene silicate.

Stability and Microbial Toxicity of Silver Nanoparticles under Denitrifying Conditions

While the antibacterial effect of silver nanoparticles (AgNPs) on environmentally beneficial microbes has drawn considerable attention, the stability and microbial toxicity of AgNPs in a system where nitrate reduction is the dominant terminal electron-accepting process remain understudied. Here, we explore the impact of citrate-coated AgNPs (cit-AgNPs) on the growth and metabolism of two metal-sensitive and one nonsensitive bacterial strains under denitrifying conditions. Dose-response analysis revealed that in contrast to the bacteriostatic effect exhibited at 1 ppm, 5 ppm cit-AgNPs were bactericidal to the metal-sensitive strains. It was observed that the growth of the cells initiated Ag(I) formation, and the supplement of chloride (2.7 mM) to the cultures substantially mitigated the bactericidal capacity of cit-AgNPs, indicating that AgNP dissolution to ionic Ag(I) played a key role in AgNP toxicity. Abiotic experiments confirmed that nitrite, not nitrate, had the capacity to oxidize cit-AgNPs. Transcriptomic analysis revealed that (i) the gene encoding for membrane stress was upregulated proportionally to cit-AgNP concentrations; (ii) cit-AgNPs and Ag(I) at higher levels upregulated genes involved in oxidative stress and iron-sulfur clusters, whereas expressions of the genes responsible for electron transport, ATP synthesis, and denitrification were substantially repressed; (iii) the addition of chloride significantly altered the level of transcriptional profiles of all of the genes. These results not only provide evidence of abiotic AgNP oxidation by metabolic intermediate nitrogen species but also suggest that AgNPs and Ag(I) may induce differential toxicity modes to prokaryotes. Our findings reinforce the importance of evaluating the potential ecological toxicity and risks associated with the transformation of nanomaterials.

Silver nanoparticles: an ecological method of synthesis, properties and use against antibiotic resistant microflora

A quantitative assessment of the antibacterial effect of silver nanoparticles on polyantibiotic-resistant grampositive and gram-negative microorganisms was carried out. Silver nanoparticles were synthesized by the environmentally friendly metal-steam synthesis method. The size and electronic state of nanoparticles were investigated by transmission electron and X-ray photoelectron spectroscopy. The antibacterial properties of nanomaterials were assessed on two clinical pathogenic strains of gram-positive and four strains of gram-negative microorganisms. The typing and assessment of bacterial resistance to antibiotics were carried out on a microbiological analyzer. The antibacterial effect of nanoparticles was quantitatively assessed using the dilution method and the determination of the minimum inhibitory and minimum bactericidal concentrations.It was found that the studied silver nanoparticles have sizes in the range from 5 to 24 nm with an average diameter of 10.8 nm. It was shown that all clinical strains of microorganisms used in the study are characterized by multiple antibacterial resistance; the percentage of their antibiotic resistance ranges from 12.5 to 93.3 %. It was found that for the studied microorganism, the values of the minimum inhibitory concentration (MIC) are in the range from 7.81 to 31.25 μg/ml, and the minimum bactericidal concentration (MBC) is in the range from 31.25 to 62.50 μg/ml. The obtained MIC and MBC data can be used to create promising antimicrobial drugs and medical next generation devices.