Antibacterial activity and toxicity of silver – nanosilver versus ionic silver

In Vitro Effects of Silver Nanoparticles on Pathogenic Bacteria and on Metabolic Activity and Viability of Human Mesenchymal Stem Cells

The rapid development of nanotechnology has led to the use of silver nanoparticles (Ag-NPs) in various biomedical fields. However, the effect of Ag-NPs on human mesenchymal stem cells (hMSCs) is not fully understood. Moreover, too frequent an exposure to products containing nanosilver in sublethal amounts raises widespread concerns that it will lead to the development of silver-resistant microorganisms. Therefore, this study aimed to evaluate the mechanism of action of Ag-NPs on hMSCs by analyzing the cellular uptake of Ag-NPs by the cells and its effect on their viability and to assess antimicrobial activity of Ag-NPs against emerging bacterial strains, including multidrug-resistant pathogens. For metabolic activity and viability evaluation, hMSCs were incubated with different concentrations of Ag-NPs (14 μg/mL, 7 μg/mL, and 3.5 μg/mL) for 10 min., 1 h and 24 h and subsequently analyzed for their viability by live-dead staining and metabolic activity by the MTS assay. The effect of Ag-NPs on bacterial pathogens was studied by determining their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). In conclusion, it was observed that exposure of hMSCs to Ag-NPs of size <10 nm has no cytotoxic effect on the metabolic activity of the cells at the concentration of 3.5 μg/mL, with minimal cytotoxic effect being observed at the concentration of 14 μg/mL after 24 h of incubation. Our findings also confirmed that Ag-NPs at the concentration of 4 μg/mL are effective broad-spectrum bactericidal agents, regardless of the antibiotic-resistance mechanism present in bacteria.

The Size-Dependent Effects of Silver Nanoparticles on Germination, Early Seedling Development and Polar Metabolite Profile of Wheat (Triticum aestivum L.)

The phytotoxicity of silver nanoparticles (Ag NPs) to plant seeds germination and seedlings development depends on nanoparticles properties and concentration, as well as plant species and stress tolerance degrees. In the present study, the effect of citrate-stabilized spherical Ag NPs (20 mg/L) in sizes of 10, 20, 40, 60, and 100 nm, on wheat grain germination, early seedlings development, and polar metabolite profile in 3-day-old seedlings were analyzed. Ag NPs, regardless of their sizes, did not affect the germination of wheat grains. However, the smaller nanoparticles (10 and 20 nm in size) decreased the growth of seedling roots. Although the concentrations of total polar metabolites in roots, coleoptile, and endosperm of seedlings were not affected by Ag NPs, significant re-arrangements of carbohydrates profiles in seedlings were noted. In roots and coleoptile of 3-day-old seedlings, the concentration of sucrose increased, which was accompanied by a decrease in glucose and fructose. The concentrations of most other polar metabolites (amino acids, organic acids, and phosphate) were not affected by Ag NPs. Thus, an unknown signal is released by small-sized Ag NPs that triggers affection of sugars metabolism and/or distribution.

Shaping and Patterning Supramolecular Materials─Stem Cell-Compatible Dual-Network Hybrid Gels Loaded with Silver Nanoparticles

Hydrogels with spatio-temporally controlled properties are appealing materials for biological and pharmaceutical applications. We make use of mild acidification protocols to fabricate hybrid gels using calcium alginate in the presence of a preformed thermally triggered gel based on a low-molecular-weight gelator (LMWG) 1,3:2:4-di(4-acylhydrazide)-benzylidene sorbitol (DBS-CONHNH₂). Nonwater-soluble calcium carbonate slowly releases calcium ions over time when exposed to an acidic pH, triggering the assembly of the calcium alginate gel network. We combined the gelators in different ways: (i) the LMWG was used as a template to spatially control slow calcium alginate gelation within preformed gel beads, using glucono-δ-lactone (GdL) to lower the pH; (ii) the LMWG was used as a template to spatially control slow calcium alginate gelation within preformed gel trays, using diphenyliodonium nitrate (DPIN) as a photoacid to lower the pH, and spatial resolution was achieved by masking. The dual-network hybrid gels display highly tunable properties, and the beads are compatible with stem cell growth. Furthermore, they preserve the LMWG function of inducing in situ silver nanoparticle (AgNP) formation, which provides the gels with antibacterial activity. These gels have potential for eventual regenerative medicine applications in (e.g.) bone tissue engineering.

Preparation of mesoporous silica-based nanocomposites with synergistically antibacterial performance from nano-metal (oxide) and polydopamine

In this work, a novel antibacterial nanocomposite system was developed using mesoporous silica (MSN) as an effective nanocarrier, and the resultant nanocomposites demonstrated remarkable antibacterial performance due to the synergistic effect among nano zinc oxides, silver nanoparticles, and polydopamine (PDA). The successful synthesis of MSN/ZnO@PDA/Ag nanocomposites was confirmed. The physicochemical properties and the morphologies of these nanocomposites were investigated. It was found that the particle size increased along with the evolution of these nanocomposites. Besides, nano zinc oxides were formed in the nanochannels of mesoporous silica with a particle size about 2 nm, and that of silver nanoparticle was less than 50 nm. In addition, the results revealed that the presence of mesoporous silica could effectively prevent the formation of large-size silver nanoparticles and facilitate their well dispersion. Due to the synergistic effect among nano zinc oxides, silver nanoparticles, and polydopamine, these nanocomposites exhibited remarkable antibacterial performance even at a low concentration of 313 ppm, and the antibacterial mechanism was also elucidated. Therefore, this work provides a facile and controllable approach to preparing synergistically antibacterial nanocomposites, and the remarkable antibacterial performance make them suitable for practical applications.

Comparison of oral microbiome profile of polymers modified with silver and vanadium base nanomaterial by next-generation sequencing

This study aimed to evaluate two methods of the incorporation of nanostructured silver vanadate decorated with silver nanoparticles (AgVO₃) into acrylic resin and characterize the profile of early and late microbial communities in class and family taxonomic level by pyrosequencing. The specimens were made by adding different concentrations of AgVO₃ (1, 2.5, and 5%) to the heat-activated acrylic resin by two methods: vacuum spatulation (VS) and polymeric film (PF). A control group (0%) without AgVO₃ was also obtained for both methods. After 24 h and 7 days of incubation in human saliva, biofilm samples were collected, DNA was extracted, and 16S rRNA genes were sequenced by the 454-Roche sequencing platform. Seventeen classes and 51 families of bacteria were identified. The abundance of Bacteroidia, Bacilli, Negativicutes, Fusobacteria and Betaproteobacteria classes decreased after 7 days of incubation, and Clostridia, Gammaproteobacteria, and unclassified bacteria increased. The Negativicutes and Betaproteobacteria classes were more abundant when the PF method was used, and Gammaproteobacteria was more abundant when VS was used. The incorporation of 5% AgVO₃ promoted a reduction in the prevalence of Bacilli, Clostridia, Negativicutes, Betaproteobacteria, and unclassified bacteria, and increased Gammaproteobacteria. The addition of AgVO₃ to acrylic resin altered the early and mature microbiome formed on the specimen surface, and the PF method presented a more favorable microbial profile than the VS method.

Evaluation of Cytotoxicity and Antibacterial Activity of a New Class of Silver Citrate-Based Compounds as Endodontic Irrigants

In the present study, the cytotoxicity and the antimicrobial activity of two silver citrate-based irrigant solutions were investigated. Cytotoxicity of various concentrations (0.25%, 0.5%, 1%, 2.5%, 5%) of both solutions (BioAKT and BioAKT Endo) was assessed on L-929 mouse fibroblasts using the MTT assay. For the quantitative analysis of components, an infrared (I.R.) spectroscopy was performed. The minimum inhibitory and minimal bactericidal concentrations (M.I.C. and M.B.C., respectively) were ascertained on Enterococcus faecalis strain ATCC 4083. For biofilm susceptibility after treatment with the irrigating agent, a minimum biofilm eradication concentration (M.B.E.C.) and confocal laser scanning microscope (C.L.S.M.) assays were performed. Quantification of E. faecalis cell biomass and percentage of live and dead cells in the biomass was appraised. Normality of data was analyzed using the D’Agostino & Pearson’s test and the Shapiro–Wilk test. Statistical analysis was performed using one-way analysis of variance (ANOVA) and Tukey’s test. Both silver citrate solutions showed mouse fibroblasts viability >70% when diluted to 0.25% and 0.5%. Conversely, at higher concentrations, they were extremely cytotoxic. F.T.-IR spectroscopy measurements of both liquids showed the same spectra, indicating similar chemical characteristics. No substantial contrast in antimicrobial activity was observed among the two silver citrate solutions by using broth microdilution methods, biofilm susceptibility (MBEC-HTP device), and biomass screening using confocal laser scanning microscopy (C.L.S.M.) technique. Both solutions, used as root canal irrigants, exhibited significant antimicrobial activity and low cytocompatibility at dilutions greater than 0.5%.

Antibacterial Property and Biocompatibility of Silver, Copper, and Zinc in Titanium Dioxide Layers Incorporated by One-Step Micro-Arc Oxidation: A Review

Titanium (Ti) and its alloys are commonly used in medical devices. However, biomaterial-associated infections such as peri-implantitis and prosthetic joint infections are devastating and threatening complications for patients, dentists, and orthopedists and are easily developed on titanium surfaces. Therefore, this review focuses on the formation of biofilms on implant surfaces, which is the main cause of infections, and one-step micro-arc oxidation (MAO) as a coating technology that can be expected to prevent infections due to the implant. Many researchers have provided sufficient data to prove the efficacy of MAO for preventing the initial stages of biofilm formation on implant surfaces. Silver (Ag), copper (Cu), and zinc (Zn) are well used and are incorporated into the Ti surface by MAO. In this review, the antibacterial properties, cytotoxicity, and durability of these elements on the Ti surface incorporated by one-step MAO will be summarized. This review is aimed at enhancing the importance of the quantitative control of Ag, Cu, and Zn for their use in implant surfaces and the significance of the biodegradation behavior of these elements for the development of antibacterial properties.

Antibacterial Activity of Silver Nanoparticles (AgNP) Confined to Mesostructured, Silica-Based Calcium Phosphate Against Methicillin-Resistant Staphylococcus Aureus (MRSA)

Staphylococcus aureus, which is commonly found in hospitals, has become a major problem in infection control. In this study, Ag/80S bioactive ceramics used for enhanced antibacterial applications have been developed. An in vitro bioactivity test of the Ag/80S bioactive ceramic powders was performed in a phosphate-buffered saline (PBS). To explore the antibacterial activity of the Ag/80S bioactive ceramic powders, the Kirby-Bauer susceptibility test, the kinetics of microbial growth analysis and the colony-forming capacity assay were used to determine their minimum inhibitory concentration (MIC) against methicillin-resistant Staphylococcus aureus (MRSA). The results confirmed that the Ag/80S bioactive ceramic powders have antibacterial activity against MRSA (ATCC 33592) and MRSA (ATCC 49476).

Anti-Methicillin-Resistant Staphylococcus aureus Nanoantibiotics

Nanoparticle-based antibiotic constructs have become a popular area of investigation in the biomedical sciences. Much of this work has pertained to human diseases, largely in the cancer therapy arena. However, considerable research has also been devoted to the nanochemistry for controlling infectious diseases. Among these are ones due to bacterial infections, which can cause serious illnesses leading to death. The onset of multi-drug-resistant (MDR) infections such as those caused by the human pathogen Staphylococcus aureus has created a dearth of problems such as surgical complications, persistent infections, and lack of available treatments. In this article, we set out to review the primary literature on the design and development of new nanoparticle materials for the potential treatment of S. aureus infections, and areas that could be further expanded upon to make nanoparticle antibiotics a mainstay in clinical settings.

Biosynthesis, characterization and antibacterial activity of silver nanoparticles by the Arctic anti-oxidative bacterium Paracoccus sp. Arc7-R13

Silver nanoparticles (AgNPs) have attracted wide interest due to its broad range of applications. This study aims to describe the biosynthesis of AgNPs using an Arctic anti-oxidative bacterium Arc7-R13 and to study its characteristics and antibacterial activity. The biosynthesis of AgNPs was verified using UV-Vis spectrum with the maximum absorption at 416 nm. The morphology of the silver nanoparticles was characterized by TEM and its characterization were investigated by EDX and FTIR. Phylogenetic analysis based on 16S rRNA gene sequence showed that strain Arc7-R13 was affiliated with genus Paracoccus. TEM analysis revealed that the AgNPs synthesized by strain Arc7-R13 were spherical and ellipsoidal in shape with size ranging from 2 to 25 nm. The optimal concentration of AgNO3 and temperature for the biosynthesis were 4 mmol/L and 37 °C, respectively. EDX analysis verified the presence of the element silver in the biosynthesized AgNPs. FTIR analysis revealed that the specific functional groups, OH, CH₃ and C≡N, might be responsible for reduction and stabilization of AgNPs. Antimicrobial test showed that the AgNPs had strong antimicrobial activity against all kinds of strains investigated, including Gram-positive Bacillus subtilis, Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa, Escherichia coli.

Plasma-Activated Aerosolized Hydrogen Peroxide (aHP) in Surface Inactivation Procedures

INTRODUCTION

Hydrogen peroxide is a strong oxidant that possesses an antimicrobial activity. It has been successfully used in surface/room decontamination processes either under the form of hydrogen peroxide vapor (HPV) or of vaporized hydrogen peroxide (VHP). Aerosolized hydrogen peroxide (aHP) offers a third alternative. The technology relies on the dispersion of aerosols of a hydrogen peroxide solution often complemented with silver cations. aHP provides an inexpensive and safe approach to treat contaminated rooms but sometimes fails to achieve the 6-log10 reduction limit in the number of viable microorganisms.

METHODS

Here, we used a venturi-based aHP generator that generates 4 mm in size aerosols from a 12% plasma-activated hydrogen peroxide solution free of silver cations.

RESULTS & DISCUSSION

We could successfully and constantly inactivate bacterial growth from biological indicators containing at least 106 spores of Geobacillus stearothermophilus placed on stainless steel discs wrapped in Tyvek pouches. We could also show that the biological indicators placed at various locations in a class II biosafety cabinet were equally inactivated, showing that hydrogen peroxide aerosols migrate through HEPA filters.

CONCLUSIONS

Considering that our method for aerosol generation is simple, reproducible, and highly effective at inactivating spores, our approach is expected to serve as a relatively cost effective alternative method for disinfecting potentially contaminated rooms or surfaces.

Ionic silver functionalized ovine forestomach matrix - a non-cytotoxic antimicrobial biomaterial for tissue regeneration applications

BACKGROUND

Antimicrobial technologies, including silver-containing medical devices, are increasingly utilized in clinical regimens to mitigate risks of microbial colonization. Silver-functionalized resorbable biomaterials for use in wound management and tissue regeneration applications have a narrow therapeutic index where antimicrobial effectiveness may be outweighed by adverse cytotoxicity. We examined the effects of ionic silver functionalization of an extracellular matrix (ECM) biomaterial derived from ovine forestomach (OFM-Ag) in terms of material properties, antimicrobial effectiveness and cytotoxicity profile.

METHODS

Material properties of OFM-Ag were assessed by via biochemical analysis, microscopy, atomic absorption spectroscopy (AAS) and differential scanning calorimetry. The silver release profile of OFM-Ag was profiled by AAS and antimicrobial effectiveness testing utilized to determine the minimum effective concentration of silver in OFM-Ag in addition to the antimicrobial spectrum and wear time. Biofilm prevention properties of OFM-Ag in comparison to silver containing collagen dressing materials was quantified via in vitro crystal violet assay using a polymicrobial model. Toxicity of ionic silver, OFM-Ag and silver containing collagen dressing materials was assessed toward mammalian fibroblasts using elution cytoxicity testing.

RESULTS

OFM-Ag retained the native ECM compositional and structural characteristic of non-silver functionalized ECM material while imparting broad spectrum antimicrobial effectiveness toward 11 clinically relevant microbial species including fungi and drug resistant strains, maintaining effectiveness over a wear time duration of 7-days. OFM-Ag demonstrated significant prevention of polymicrobial biofilm formation compared to non-antimicrobial and silver-containing collagen dressing materials. Where silver-containing collagen dressing materials exhibited cytotoxic effects toward mammalian fibroblasts, OFM-Ag was determined to be non-cytotoxic, silver elution studies indicated sustained retention of silver in OFM-Ag as a possible mechanism for the attenuated cytotoxicity.

CONCLUSIONS

This work demonstrates ECM biomaterials may be functionalized with silver to favourably shift the balance between detrimental cytotoxic potential and beneficial antimicrobial effects, while preserving the ECM structure and function of utility in tissue regeneration applications.

Coating of Polyetheretherketone Films with Silver Nanoparticles by a Simple Chemical Reduction Method and Their Antibacterial Activity

The coating of polymeric substrate polyetheretherketone (PEEK) with silver nanoparticles (AgNPs) was carried out by a wet chemical route at room temperature. The coating process was developed from the Tollens reagent and D-glucose as reducing agent. The resulting composite exhibited antimicrobial activity. The PEEK films were coated with a single layer and two layers of silver nanoparticles in various concentrations. The crystallographic properties of the polymer and the silver nanoparticles were analyzed by X-ray diffraction (XRD). Fourier transform infrared spectra (FTIR) show the interaction between the silver nanoparticles with the polymeric substrate. Transmission electron microscope (TEM) images confirmed the obtaining of metallic nanoparticles with average sizes of 25 nm. It was possible to estimate the amount of silver deposited on PEEK with the help of thermogravimetric analysis. The morphology and shape of the AgNPs uniformly deposited on the PEEK films was ascertained by the techniques of scanning electron microscopy (SEM) and atomic force microscopy (AFM), evidencing the increase in the amount of silver by increasing the concentration of the metal precursor. Finally, the antibacterial activity of the films coated with Ag in Escherichia coli, Serratia marcescens and Bacillus licheniformis was evaluated, evidencing that the concentration of silver is crucial in the cellular replication of the bacteria.

Plasmon Resonance of Silver Nanoparticles as a Method of Increasing Their Antibacterial Action

In this article, a series of silver-containing dressings are prepared by metal-vapor synthesis (MVS), and their antibacterial properties are investigated. The antibacterial activity of the dressings containing silver nanoparticles (AgNPs) against some Gram-positive, and Gram-negative microorganisms (Staphylococcus aureus, Staphylococcus haemolyticus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Moraxella spp.) has been determined. Based on the plasmon resonance frequency of these nanoparticles, the frequency of laser irradiation of the dressing was chosen. The gauze bandage examined showed pronounced antibacterial properties, especially to Staphylococcus aureus strain. When 470 nm laser radiation, with a power of 5 mW, was applied for 5 min, 4 h after inoculating the Petri dish, and placing a bandage containing silver nanoparticles on it, the antibacterial effect of the latter significantly increased—both against Gram-positive and Gram-negative microorganisms. The structure and chemical composition of the silver-containing nanocomposite were studied by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS). The synthesized AgNPs demonstrate narrow and monomodal particle size distribution with an average size of 1.75 nm. Atoms of metal in Ag/bandage system are mainly in Ag⁰ state, and the oxidized atoms are in the form of Ag-Ag-O groups.

Metal TiO2 Nanotube Layers for the Treatment of Dental Implant Infections

Titanium oxide nanotube layers with silver and zinc nanoparticles are attracting increasing attention in the design of bone and dental implants due to their antimicrobial potential and their ability to control host cell adhesion, growth, and differentiation. However, recent reports indicate that the etiology of dental infections is more complex than has been previously considered. Therefore, the antimicrobial potential of dental implants should be evaluated against at least several different microorganisms cooperating in human mouth colonization. In this study, Ag and Zn nanoparticles incorporated into titanium oxide nanotubular layers were studied with regard to how they affect Candida albicans, Candida parapsilosis, and Streptococcus mutans. Layers of titanium oxide nanotubes with an average diameter of 110 nm were fabricated by electrochemical anodization, annealed at 650 °C, and modified with approx. 5 wt % Ag or Zn nanoparticles. The surfaces were examined with the scanning electron microscopy-energy dispersive X-ray analysis, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy techniques and subjected to evaluation of microbial-killing and microbial adhesion-inhibiting potency. In a 1.5 h long adhesion test, the samples were found more effective toward yeast strains than toward S. mutans. In a release-killing test, the microorganisms were almost completely eliminated by the samples, either within 3 h of contact (for S. mutans) or 24 h of contact (for both yeast strains). Although further improvement is advisable, it seems that Ag and Zn nanoparticles incorporated into TiO₂ nanotubular surfaces provide a powerful tool for reducing the incidence of bone implant infections. Their high bidirectional activity (against both Candida species and S. mutans) makes the layers tested particularly promising for the design of dental implants.

Elemental ion release and cytotoxicity of antimicrobial acrylic resins incorporated with nanomaterial

OBJECTIVES

This study evaluated the release of ions and the cytotoxicity of acrylic resins incorporated with silver vanadate decorated with silver nanoparticles (AgVO₃ ).

BACKGROUND

The inhibition of the accumulation of microorganisms on the resins is critical in preventing diseases. However, the hypothesis is that the release of ions from the incorporation of AgVO₃ may be important in biocompatibility.

MATERIALS AND METHODS

Specimens of autopolymerising (AP) and heat-polymerising resin (HP) with AgVO₃ were prepared and immersed in culture medium. The release of silver ions (Ag) and vanadium (V) was evaluated by mass spectrometry with inductively coupled plasma (ICP-MS) (n=9) and the cell viability of fibroblasts L929 by MTT (3-[4,5-dimethylthiazol- 2yl]-2,5-diphenyltetrazolium bromide) (n=12). The results were evaluated with analysis of variance (ANOVA), Tukey and Pearson correlation test (α=.05).

RESULTS

The groups containing AgVO₃ presented a difference in relation to the control (0%) regarding the release of Ag and V (P<.0001). All groups showed a reduction in L929 viability when compared with the cellular control (100%) (P<.0001). In comparison with the control resins for HP, a reduction in the metabolism of cells occurred starting at 2.5% and for AP at 5% (P<.0001). A positive correlation was found between the concentration of AgVO₃ and the ion release, and a negative between the ion release and the cell viability.

CONCLUSIONS

Significant numbers of Ag and V ions were released from resins with higher concentrations of AgVO₃ , presenting cytotoxicity for cells, suggesting that the use of low concentrations is indicated to avoid risks to patients.

Influence of silver content on rifampicin adsorptivity for magnetite/Ag/rifampicin nanoparticles

Magnetite nanoparticles (NPs) decorated with silver (magnetite/Ag) are intensively investigated due to their application in the biomedical field. We demonstrate that the increase of silver content on the surface of nanoparticles improves the adsorptivity of antibiotic rifampicin as well as antibacterial properties. The use of ginger extract allowed to improve the silver nucleation on the magnetite surface that resulted in an increase of silver content. Physicochemical and functional characterization of magnetite/Ag NPs was performed. Our results show that 5%-10% of silver content in magnetite/Ag NPs is already sufficient for antimicrobial properties against Streptococcus salivarius and Staphylococcus aureus. The rifampicin molecules on the magnetite/Ag NPs surface made the spectrum of antimicrobial activity wider. Cytotoxicity evaluation of the magnetite/Ag/rifampicin NPs showed no harmful action towards normal human fibroblasts, whereas the effect on human embryonic kidney cell viability was time and dose dependent.

Non-Equilibrium Plasma Processing for the Preparation of Antibacterial Surfaces

Non-equilibrium plasmas offer several strategies for developing antibacterial surfaces that are able to repel and/or to kill bacteria. Due to the variety of devices, implants, and materials in general, as well as of bacteria and applications, plasma assisted antibacterial strategies need to be tailored to each specific surface. Nano-composite coatings containing inorganic (metals and metal oxides) or organic (drugs and biomolecules) compounds can be deposited in one step, and used as drug delivery systems. On the other hand, functional coatings can be plasma-deposited and used to bind antibacterial molecules, for synthesizing surfaces with long lasting antibacterial activity. In addition, non-fouling coatings can be produced to inhibit the adhesion of bacteria and reduce the formation of biofilm. This paper reviews plasma-based strategies aimed to reduce bacterial attachment and proliferation on biomedical materials and devices, but also onto materials used in other fields. Most of the activities described have been developed in the lab of the authors.

Influence of antibiotic adsorption on biocidal activities of silver nanoparticles

Excessive use of antibiotics has posed two major challenges in public healthcare. One of them is associated with the development of multi-drug resistance while the other one is linked to side effects. In the present investigation, the authors report an innovative approach to tackle the challenges of multi-drug resistance and acute toxicity of antibiotics by using antibiotics adsorbed metal nanoparticles. Monodisperse silver nanoparticles (SNPs) have been synthesised by two-step process. In the first step, SNPs were prepared by chemical reduction of AgNO3 with oleylamine and in the second step, oleylamine capped SNPs were phase-transferred into an aqueous medium by ligand exchange. Antibiotics - tetracycline and kanamycin were further adsorbed on the surface of SNPs. Antibacterial activities of SNPs and antibiotic adsorbed SNPs have been investigated on gram-positive (Staphylococcus aureus, Bacillus megaterium, Bacillus subtilis), and gram-negative (Proteus vulgaris, Shigella sonnei, Pseudomonas fluorescens) bacterial strains. Synergistic effect of SNPs on antibacterial activities of tetracycline and kanamycin has been observed. Biocidal activity of tetracycline is improved by 0-346% when adsorbed on SNPs; while for kanamycin, the improvement is 110-289%. This synergistic effect of SNPs on biocidal activities of antibiotics may be helpful in reducing their effective dosages.

Effect of Storage in Distilled Water for Three Months on the Antimicrobial Properties of Poly(methyl methacrylate) Denture Base Material Doped with Inorganic Filler

The colonization of poly(methyl methacrylate) (PMMA) denture base materials by pathogenic microorganisms is a major problem associated with the use of prostheses, and the incorporation of antimicrobial fillers is a method of improving the antimicrobial properties of these materials. Numerous studies have demonstrated the initial in vitro antimicrobial effectiveness of this type of material; however, reports demonstrating the stability of these fillers over longer periods are not available. In this study, silver sodium hydrogen zirconium phosphate was introduced into the powder component of a PMMA denture base material at concentrations of 0.25%, 0.5%, 1%, 2%, 4%, and 8% (w/w). The survival rates of the gram-positive bacterium Staphylococcus aureus, gram-negative bacterium Escherichia coli and yeast-type fungus Candida albicans were established after fungal or bacterial suspensions were incubated with samples that had been previously stored in distilled water. Storage over a three-month period led to the progressive reduction of the initial antimicrobial properties. The results of this study suggest that additional microbiological tests should be conducted for materials that are treated with antimicrobial fillers and intended for long-term use. Future long-term studies of the migration of silver ions from the polymer matrix and the influence of different media on this ion emission are required.

Synthesis and characterization of magnetite/silver/antibiotic nanocomposites for targeted antimicrobial therapy

The article is devoted to preparation and characterization of magnetite/silver/antibiotic nanocomposites for targeted antimicrobial therapy. Magnetite nanopowder was produced by thermochemical technique; silver was deposited on the magnetite nanoparticles in the form of silver clusters. Magnetite/silver nanocomposite was investigated by XRD, SEM, TEM, AFM, XPS, EDX techniques. Adsorptivity of magnetite/silver nanocomposite towards seven antibiotics from five different groups was investigated. It was shown that rifampicin, doxycycline, ceftriaxone, cefotaxime and doxycycline may be attached by physical adsorption to magnetite/silver nanocomposite. Electrostatic surfaces of antibiotics were modeled and possible mechanism of antibiotic attachment is considered in this article. Raman spectra of magnetite, magnetite/silver and magnetite/silver/antibiotic were collected. It was found that it is difficult to detect the bands related to antibiotics in the magnetite/silver/antibiotic nanocomposite spectra due to their overlap by the broad carbon bands of magnetite nanopowder. Magnetic measurements revealed that magnetic saturation of the magnetite/silver/antibiotic nanocomposites decreased on 6-19 % in comparison with initial magnetite nanopowder. Pilot study of antimicrobial properties of the magnetite/silver/antibiotic nanocomposites were performed towards Bacillus pumilus.

Toxicity of fullerene and nanosilver nanomaterials against bacteria associated to the body surface of the estuarine worm Laeonereis acuta (Polychaeta, Nereididae)

This study analyzed the growth and biochemical responses of six bacterial colonies isolated from the mucus of the estuarine polychaeta Laeonereis acuta (Nereididae) after exposure to a water suspension of fullerene (nC60) and nanosilver (nAg) separately (0.01; 0.10; and 1.00 mg/L) and together (0.01; 0.10; and 1.00 mg/L of nanosilver and 1.00 mg/L of fullerene added to each nAg concentration). Exposures were performed in darkness during 24 h and then samples were taken from the worms and inoculated on agar during 24 h to analyze colonies growth. After this the material was analyzed biochemically. Colonies growth (tested by wet biomass weight) was inhibited at 0.01 and 0.10 mg/L of nAg and 0.01 and 0.10 mg/L nAg + constant 1.00 mg/L of nC60 (p < 0.05). Lipid peroxidation damage was significant from the control for the concentrations of 0.01 and 0.10 mg/L of nC60 and glutathione-S-transferase (GST) activity was significantly higher for the concentration of 1.00 mg/L mg/L nAg + constant 1.00 mg/L of nC60 (p < 0.05). Although nC60 did not induced growth inhibition, it triggered lipid peroxidation alone and increased GST activity together with nAg.60 Contrary to nC60, nanosilver inhibited bacterial growth, although the biochemical measurements indicate that this response is not due to reactive oxygen species generation.

Silver nanoparticles: therapeutical uses, toxicity, and safety issues

The promises of nanotechnology have been realized to deliver the greatest scientific and technological advances in several areas. The biocidal activity of Metal nanoparticles in general and silver nanoparticles (AgNPs) depends on several morphological and physicochemical characteristics of the particles. Many of the interactions of the AgNPs with the human body are still poorly understood; consequently, the most desirable characteristics for the AgNPs are not yet well established. Therefore, the development of nanoparticles with well-controlled morphological and physicochemical features for application in human body is still an active area of interdisciplinary research. Effects of the development of technology of nanostructured compounds seem to be so large and comprehensive that probably it will impact on all fields of science and technology. However, mechanisms of safety control in application, utilization, responsiveness, and disposal accumulation still need to be further studied in-depth to ensure that the advances provided by nanotechnology are real and liable to provide solid and consistent progress. This review aims to discuss AgNPs applied in biomedicine and as promising field for insertion and development of new compounds related to medical and pharmacy technology. The review also addresses drug delivery, toxicity issues, and the safety rules concerning biomedical applications of silver nanoparticles.

Poly(ethylene oxide)-b-poly(propylene oxide) amphiphilic block copolymer-mediated growth of silver nanoparticles and their antibacterial behavior

Silver nanoparticles were grown in self-assembled amphiphilic poly(ethylene oxide)/poly(propylene oxide) (PEO/PPO) triblock copolymers in selective solvents. Ternary systems of block copolymer, water, and p-xylene were used, forming a dispersion of water droplets in oil (reverse micellar) as well as binary water/block copolymer solutions. Besides its stabilizing affect, the role of the copolymer as a reducing agent for the metal salt precursors was examined. It was found that block copolymer-enabled reduction, carried out mainly by the PEO blocks, could take place only under particular conditions mostly related to the metal precursor, the block copolymer concentration, and the self-assembled micellar configuration. The effect of the triblock copolymers on growth and stabilization of gold nanoparticles was also examined. The antibacterial effect of the silver nanoparticles was investigated against Escherichia coli cells, and their performance was evaluated through a series of parametrization experiments, including the effect of the metal concentration, stability, activity over time, and dosage, while particular emphasis was given on the role of ions versus nanoparticles on the antibacterial performance.

Sorption, solubility, bond strength and hardness of denture soft lining incorporated with silver nanoparticles

The colonization of denture soft lining material by oral fungi can result in infections and stomatitis of oral tissues. In this study, 0 ppm to 200 ppm of silver nanoparticles was incorporated as an antimicrobial agent into composites to reduce the microbial colonization of lining materials. The effect of silver nanoparticle incorporation into a soft lining material on the sorption, solubility, hardness (on the Shore A scale) and tensile bond strength of the composites was investigated. The data were statistically analyzed using two-way ANOVA and Newman-Keuls post hoc tests or the chi-square Pearson test at the p < 0.05 level. An increase in the nanosilver concentration resulted in a decrease in hardness, an increase in sorption and solubility, a decrease in bond strength and a change in the failure type of the samples. The best combination of bond strength, sorption, solubility and hardness with antifungal efficacy was achieved for silver nanoparticle concentrations ranging from 20 ppm to 40 ppm. These composites did not show properties worse than those of the material without silver nanoparticles and exhibited enhanced in vitro antifungal efficiency.