Impact of heat on nanocrystalline silver dressings

Treatment of infection and inflammation associated with COVID-19, multi-drug resistant pneumonia and fungal sinusitis by nebulizing a nanosilver solution

Solutions containing Ag⁰ nanoclusters, Ag⁺¹, and higher oxidation state silver, generated from nanocrystalline silver dressings, were anti-inflammatory against porcine skin inflammation. The dressings have clinically-demonstrated broad-spectrum antimicrobial activity, suggesting application of nanosilver solutions in treating pulmonary infection. Nanosilver solutions were tested for antimicrobial efficacy; against HSV-1 and SARS-CoV-2; and nebulized in rats with acute pneumonia. Patients with pneumonia (ventilated), fungal sinusitis, burns plus COVID-19, and two non-hospitalized patients with COVID-19 received nebulized nanosilver solution. Nanosilver solutions demonstrated pH-dependent antimicrobial efficacy; reduced infection and inflammation without evidence of lung toxicity in the rat model; and inactivated HSV-1 and SARS-CoV-2. Pneumonia patients had rapidly reduced pulmonary symptoms, recovering pre-illness respiratory function. Fungal sinusitis-related inflammation decreased immediately with infection clearance within 21 days. Non-hospitalized patients with COVID-19 experienced rapid symptom remission. Nanosilver solutions, due to anti-inflammatory, antiviral, and antimicrobial activity, may be effective for treating respiratory inflammation and infections caused by viruses and/or microbes.

Chemical design principles of next-generation antiviral surface coatings

The ongoing coronavirus disease 2019 (COVID-19) pandemic has accelerated efforts to develop high-performance antiviral surface coatings while highlighting the need to build a strong mechanistic understanding of the chemical design principles that underpin antiviral surface coatings. Herein, we critically summarize the latest efforts to develop antiviral surface coatings that exhibit virus-inactivating functions through disrupting lipid envelopes or protein capsids. Particular attention is focused on how cutting-edge advances in material science are being applied to engineer antiviral surface coatings with tailored molecular-level properties to inhibit membrane-enveloped and non-enveloped viruses. Key topics covered include surfaces functionalized with organic and inorganic compounds and nanoparticles to inhibit viruses, and self-cleaning surfaces that incorporate photocatalysts and triplet photosensitizers. Application examples to stop COVID-19 are also introduced and demonstrate how the integration of chemical design principles and advanced material fabrication strategies are leading to next-generation surface coatings that can help thwart viral pandemics and other infectious disease threats.

Biomediated synthesis, characterization, and biological applications of nickel oxide nanoparticles derived from Toona ciliata, Ficus carica and Pinus roxburghii

Biomediated ecofriendly method for the synthesis of nickel oxide nanoparticles using plants extracts (Toona ciliata, Ficus carica and Pinus roxburghii) has been reported. The nanoparticles so obtained were characterized by various techniques such as ultraviolet-visible, powder X-ray diffraction, Fourier transform infrared spectroscopy, attenuated total reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis and fluorescence spectroscopy. Formation of nickel oxide nanoparticles was confirmed by Fourier transform infrared spectroscopy and X-ray diffraction where the former technique ascertains the formation of bond between nickel and oxygen. The nickel oxide nanoparticles were found to be crystalline cubic face centered and show intense photoluminescence emission at 416, 414 and 413 nm, respectively. The antibacterial activity was studied against gram positive and gram negative bacterial species by agar well diffusion method. The nickel oxide nanoparticles show better activity against some bacterial strains with reference to the standard drugs Ciprofloxacin and Gentamicin. The anthelmintic activity against Pheretima posthuma of nanomaterials obtained from Pinus roxburghii was found to be greater than that derived from Toona ciliata and Ficus carica using the standard drug Albendazole. This method takes the advantage of the sustainable and economic approach for the synthesis of metal oxide nanoparticles.

Phyto-fabrication, purification, characterisation, optimisation, and biological competence of nano-silver

Published studies indicate that virtually any kind of botanical material can be exploited to make biocompatible, safe, and cost-effective silver nanoparticles. This hypothesis is supported by the fact that plants possess active bio-ingredients that function as powerful reducing and coating agents for Ag+. In this respect, a phytomediation method provides favourable monodisperse, crystalline, and spherical particles that can be easily purified by ultra-centrifugation. However, the characteristics of the particles depend on the reaction conditions. Optimal reaction conditions observed in different experiments were 70-95 °C and pH 5.5-8.0. Green silver nanoparticles (AgNPs) have remarkable physical, chemical, optical, and biological properties. Research findings revealed the versatility of silver particles, ranging from exploitation in topical antimicrobial ointments to in vivo prosthetic/organ implants. Advances in research on biogenic silver nanoparticles have led to the development of sophisticated optical and electronic materials with improved efficiency in a compact configuration. So far, eco-toxicity of these nanoparticles is a big challenge, and no reliable method to improve the toxicity has been reported. Therefore, there is a need for reliable models to evaluate the effect of these nanoparticles on living organisms.

Photothermal-assisted antibacterial application of graphene oxide-Ag nanocomposites against clinically isolated multi-drug resistant Escherichia coli

In the field of public health, treatment of multidrug-resistant (MDR) bacterial infection is a great challenge. Herein, we provide a solution to this problem with the use of graphene oxide-silver (GO-Ag) nanocomposites as antibacterial agent. Following established protocols, silver nanoparticles were grown on graphene oxide sheets. Then, a series of in vitro studies were conducted to validate the antibacterial efficiency of the GO-Ag nanocomposites against clinical MDR Escherichia coli (E. coli) strains. GO-Ag nanocomposites showed the highest antibacterial efficiency among tested antimicrobials (graphene oxide, silver nanoparticles, GO-Ag), and synergetic antibacterial effect was observed in GO-Ag nanocomposites treated group. Treatment with 14.0 µg ml-1 GO-Ag could greatly inhibit bacteria growth; remaining bacteria viabilities were 4.4% and 4.1% for MDR-1 and MDR-2 E. coli bacteria, respectively. In addition, with assistance of photothermal effect, effective sterilization could be achieved using GO-Ag nanocomposites as low as 7.0 µg ml-1. Fluorescence imaging and morphology characterization uncovered that bacteria integrity was disrupted after GO-Ag nanocomposites treatment. Cytotoxicity results of GO-Ag using human-derived cell lines (HEK 293T, Hep G2) suggested more than 80% viability remained at 7.0 µg ml-1. All the results proved that GO-Ag nanocomposites are efficient antibacterial agent against multidrug-resistant E. coli.

Leaf Extract of Dillenia indica as a Source of Selenium Nanoparticles with Larvicidal and Antimicrobial Potential toward Vector Mosquitoes and Pathogenic Microbes

Chikungunya, dengue, Zika, malaria, Japanese encephalitis, filariasis, West Nile, etc. are mosquito transmitted diseases that have killed millions of people worldwide, and millions of people are at risk of these diseases. Control of the mosquitoes, such as Aedes aegypti and Culex quinquefasciatus, is challenging due to their development of resistance to synthetic insecticides. The habitats of the young mosquitoes are also the habitats for foodborne pathogens like Staphylococcus aureus (MTCC96) and Serratia marcescens (MTCC4822). The present study was aimed at synthesizing eco-friendly green nanoparticles using Dillenia indica leaf broth and analyzing its efficacy in controlling the vector mosquitoes A. aegypti and C. quinquefasciatus, as well as the microbial pathogens St. aureus and Se. marcescens. The formation of selenium nanoparticles (SeNps) was confirmed using UV-Vis spectroscopy (absorption peak at 383.00 nm), Fourier transform infrared radiation (FTIR spectrum peaks at 3177, 2114, 1614, 1502, 1340, 1097, 901, 705, and 508 cm−1), X-ray diffraction (diffraction peaks at 23.3 (100), 29.6 (101), 43.5 (012), and 50.05 (201)), and scanning electron microscopy (oval shaped). The size of the nanoparticles and their stability were analyzed using dynamic light scattering (Z-Average value of 248.0 nm) and zeta potential (−13.2 mV). The SeNps disorganized the epithelial layers and have broken the peritrophic membrane. Histopathological changes were also observed in the midgut and caeca regions of the SeNPs treated A. aegypti and C. quinquefasciatus larvae. The SeNps were also active on both the bacterial species showing strong inhibitory zones. The present results will explain the ability of SeNps in controlling the mosquitoes as well as the bacteria and will contribute to the development of multi potent eco-friendly compounds.

Effect of Biosynthesized ZnO Nanoparticles on Multi-Drug Resistant Pseudomonas Aeruginosa

Synthesis of nanoparticles using the plants has several advantages over other methods due to the environmentally friendly nature of plants. Besides being environmentally friendly, the synthesis of nanoparticles using plants or parts of the plants is also cost effective. The present study focuses on the biosynthesis of zinc oxide nanoparticles (ZnO NPs) using the seed extract of Butea monsoperma and their effect on to the quorum-mediated virulence factors of multidrug-resistant clinical isolates of Pseudomonas aeruginosa at sub minimum inhibitory concentration (MIC). The synthesized ZnO NPs were characterized by different techniques, such as Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and transmission electron microscopy (TEM). The average size of the nanoparticles was 25 nm as analyzed by TEM. ZnO NPs at sub MIC decreased the production of virulence factors such as pyocyanin, protease and hemolysin for P. aeruginosa (p ≤ 0.05). The interaction of NPs with the P. aeruginosa cells on increasing concentration of NPs at sub MIC levels showed greater accumulation of nanoparticles inside the cells as analyzed by TEM.

Antimicrobial Activity of Silver-Treated Bacteria against other Multi-Drug Resistant Pathogens in Their Environment

Silver is a potent antimicrobial agent against a variety of microorganisms and once the element has entered the bacterial cell, it accumulates as silver nanoparticles with large surface area causing cell death. At the same time, the bacterial cell becomes a reservoir for silver. This study aims to test the microcidal effect of silver-killed E. coli O104: H4 and its supernatant against fresh viable cells of the same bacterium and some other species, including E. coli O157: H7, Multidrug Resistant (MDR) Pseudomonas aeruginosa and Methicillin Resistant Staphylococcus aureus (MRSA). Silver-killed bacteria were examined by Transmission Electron Microscopy (TEM). Agar well diffusion assay was used to test the antimicrobial efficacy and durability of both pellet suspension and supernatant of silver-killed E. coli O104:H4 against other bacteria. Both silver-killed bacteria and supernatant showed prolonged antimicrobial activity against the tested strains that extended to 40 days. The presence of adsorbed silver nanoparticles on the bacterial cell and inside the cells was verified by TEM. Silver-killed bacteria serve as an efficient sustained release reservoir for exporting the lethal silver cations. This promotes its use as a powerful disinfectant for polluted water and as an effective antibacterial which can be included in wound and burn dressings to overcome the problem of wound contamination.

Use of internally validated in vitro biofilm models to assess antibiofilm performance of silver-containing gelling fibre dressings

Objective:

To assess the efficacy of five silver-containing gelling fibre wound dressings against single-species and multispecies biofilms using internally validated, UKAS-accredited in vitro test models.

Method:

Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans single- and multispecies biofilms were cultured using Centres for Disease Control (CDC) biofilm reactors and colony drip flow reactors (CDFR). Following a 72 hour incubation period, the substrates on which biofilms were grown were rinsed to remove planktonic microorganisms and then challenged with fully hydrated silver-containing gelling fibre wound dressings. Following dressing application for 24 or 72 hours, remaining viable organisms from the treated biofilms were quantified.

Results:

In single-species in vitro models, all five antimicrobial dressings were effective in eradicating Staphylococcus aureus and Pseudomonas aeruginosa biofilm bacteria. However, only one of the five dressings (Hydrofiber technology with combination antibiofilm/antimicrobial technology) was able to eradicate the more tolerant single-species Candida albicans biofilm. In a more complex and stringent CDFR biofilm model, the hydrofiber dressing with combined antibiofilm/antimicrobial technology was the only dressing that was able to eradicate multispecies biofilms such that no viable organisms were recovered.

Conclusion:

Given the detrimental effects of biofilm on wound healing, stringent in vitro biofilm models are increasingly required to investigate the efficacy of antimicrobial dressings. Using accredited in vitro biofilm models of increasing complexity, differentiation in the performance of dressings with combined antibiofilm/antimicrobial technology against those with antimicrobial properties alone, was demonstrated.

Wound dressings functionalized with silver nanoparticles: promises and pitfalls

Infections are the main reason why most people die from burns and diabetic wounds. The clinical challenge for treating wound infections through traditional antibiotics has been growing steadily and has now reached a critical status requiring a paradigm shift for improved chronic wound care. The US Centers for Disease Control have predicted more deaths from antimicrobial-resistant bacteria than from all types of cancers combined by 2050. Thus, the development of new wound dressing materials that do not rely on antibiotics is of paramount importance. Currently, incorporating nanoparticles into scaffolds represents a new concept of 'nanoparticle dressing' which has gained considerable attention for wound healing. Silver nanoparticles (Ag-NPs) have been categorized as metal-based nanoparticles and are intriguing materials for wound healing because of their excellent antimicrobial properties. Ag-NPs embedded in wound dressing polymers promote wound healing and control microorganism growth. However, there have been several recent disadvantages of using Ag-NPs to fight infections, such as bacterial resistance. This review highlights the therapeutic approaches of using wound dressings functionalized with Ag-NPs and their potential role in revolutionizing wound healing. Moreover, the physiology of the skin and wounds is discussed to place the use of Ag-NPs in wound care into perspective.

New Antibacterial Paper Made of Silver Phosphate Cellulose Fibers: A Preliminary Study on the Elimination of Staphylococcus aureus Involved in Diabetic Foot Ulceration

AIM

To evaluate in vitro the antibacterial effect of a paper made of silver phosphate cellulose fibers (SPCF) on Staphylococcus aureus, the most common diabetic foot ulceration (DFU) pathogen when compared with other common commercial products.

METHODS

The antibacterial activity of SPCF samples was evaluated through time with cell counting on agar plates. SPCF samples were then compared with commercial wound care products currently in use in DFU treatments (Silvercel™, Acticoat 7, and Aquacel Ag ExtraTM) through time on agar plates (growth inhibition zones).

RESULTS

After 6 hours, there was no viable bacterial cell detected on either plate (p < 0.05). There was a net growth inhibition zone for SPCF samples but no significant difference between the two silver concentrations. Compared with common commercial products, SPCF paper provides results equal to Acticoat 7 (p < 0.05). There was a net growth inhibition zone for SPCF samples but no significant difference between the two silver concentrations. Compared with common commercial products, SPCF paper provides results equal to Acticoat 7 (p < 0.05). There was a net growth inhibition zone for SPCF samples but no significant difference between the two silver concentrations. Compared with common commercial products, SPCF paper provides results equal to Acticoat 7 (.

CONCLUSIONS

These results have shown the efficiency of SPCF paper to eliminate Staphylococcus aureus in these conditions. SPCF papers are effective when compared with other common commercial products and could have an industrial potential in wound care. Infected DFU could benefit from the antibacterial effectiveness of SPCF, but more relevant experimentations related to foot ulcers are needed.Staphylococcus aureus, the most common diabetic foot ulceration (DFU) pathogen when compared with other common commercial products.

Chemical and Physical Transformations of Silver Nanomaterial Containing Textiles After Modeled Human Exposure

The antimicrobial properties of silver nanomaterials (AgNM) have been exploited in various consumer applications, including textiles such as wound dressings. Understanding how these materials chemically transform throughout their use is necessary to predict their efficacy during use and their behavior after disposal. The aim of this work was to evaluate chemical and physical transformations to a commercial AgNM-containing wound dressing during modeled human exposure to synthetic sweat (SW) or simulated wound fluid (WF). Scanning electron microscopy with energy dispersive X-ray spectroscopy (EDS) revealed the formation of micrometer-sized structures at the wound dressing surface after SW exposure while WF resulted in a largely featureless surface. Measurements by X-ray photoelectron spectroscopy (XPS) revealed a AgCl surface (consistent with EDS) while X-ray diffraction (XRD) found a mixture of zero valent silver and AgCl suggesting the AgNM wound dressings surface formed a passivating AgCl surface layer after SW and WF exposure. For WF, XPS based findings revealed the addition of an adsorbed protein layer based on the nitrogen marker which adsorbed released silver at prolonged exposures. Silver release was evaluated by inductively coupled plasma mass spectrometry which revealed a significant released silver fraction in WF and minimal released silver in SW. Analysis suggests that the protein in WF sequestered a fraction of the released silver which continued with exposure time, suggesting additional processing at the wound dressing surface even after the initial transformation to AgCl. To evaluate the impact on antimicrobial efficacy, zone of inhibition (ZOI) testing was conducted which found no significant change after modeled human exposure compared to the pristine wound dressing. The results presented here suggest AgNM-containing wound dressings transform chemically in simulated human fluids resulting in a material with comparable antimicrobial properties with pristine wound dressings. Ultimately, knowing the resulting chemical properties of the AgNM wound dressings will allow better predictive models to be developed regarding their fate.

Perspectives on antibacterial performance of silver nanoparticle-loaded three-dimensional polymeric constructs

Silver nanoparticle (AgNP)-loaded polymeric constructs are widely investigated for potential applications as drug delivery systems, wound dressings, and antibiofouling biomaterials. Herein, the authors present several methods for fabricating such materials and evaluate their efficacy against Escherichia coli. H₂O_(v) plasma surface modification is employed to enhance material surface wettability (explored by water contact angle goniometry) and nanoparticle incorporation. Compositional analyses reveal that incorporation of AgNPs on the surface and bulk of the materials strongly depends on the fabrication methodology. More importantly, the nature of AgNP incorporation into the polymer has direct implications on the biocidal performance resulting from the release of Ag⁺. The materials fabricated herein fell significantly short of healthcare standards with respect to antimicrobial behavior, and, in comparing their results to numerous literature studies, the authors identified a glaring disparity in the way such results are often described. Thus, this work also contains a critical evaluation of the literature, highlighting select poor-performing materials to demonstrate several shortcomings in the quantitative analysis and reporting of the antibacterial efficacy of AgNP-loaded materials. Ultimately, recommendations for best practices for better evaluation of these constructs toward improved antibacterial efficacy in medical settings are provided.

Effect of Silver-Emitting Filler on Antimicrobial and Mechanical Properties of Soft Denture Lining Material

Colonization of silicone-based soft lining materials by pathogenic yeast-type fungi is a common problem associated with the use of dentures. In this study, silver sodium hydrogen zirconium phosphate (SSHZP) was introduced into polydimethylsiloxane-based material as an antimicrobial filler at concentrations of 0.25, 0.5, 1, 2, 4, 6, 8, 10, 12, and 14% (w/w). The in vitro antimicrobial efficacy was investigated. Candida albicans was used as a characteristic representative of pathogenic oral microflora. Staphylococcus aureus and Escherichia coli were used as the typical Gram-positive and Gram-negative bacterial strains, respectively. The effect of filler addition on the Shore A hardness, tensile strength, tensile bond strength, sorption, and solubility was investigated. An increase in the filler concentration resulted in an increase in hardness, sorption, and solubility, and for the highest concentration, a decrease in bond strength. The favorable combination of antimicrobial efficacy with other properties was achieved at filler concentrations ranging from 2% to 10%. These composites exhibited mechanical properties similar to the material without the antimicrobial filler and enhanced in vitro antimicrobial efficiency.

Functionalized ZnO Nanoparticles with Gallic Acid for Antioxidant and Antibacterial Activity against Methicillin-Resistant S. aureus

In this study, we report a new multifunctional nanoparticle with antioxidative and antibacterial activities in vitro. ZnO@GA nanoparticles were fabricated by coordinated covalent bonding of the antioxidant gallic acid (GA) on the surface of ZnO nanoparticles. This addition imparts both antioxidant activity and high affinity for the bacterial cell membrane. Antioxidative activities at various concentrations were evaluated using a 2,2'-azino-bis(ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging method. Antibacterial activities were evaluated against Gram-positive bacteria (Staphylococcus aureus: S. aureus), including several strains of methicillin-resistant S. aureus (MRSA), and Gram-negative bacteria (Escherichia coli). The functionalized ZnO@GA nanoparticles showed good antioxidative activity (69.71%), and the bactericidal activity of these nanoparticles was also increased compared to that of non-functionalized ZnO nanoparticles, with particularly effective inhibition and high selectivity for MRSA strains. The results indicate that multifunctional ZnO nanoparticles conjugated to GA molecules via a simple surface modification process displaying both antioxidant and antibacterial activity, suggesting a possibility to use it as an antibacterial agent for removing MRSA.

Potential applications and human biosafety of nanomaterials used in nanomedicine

With the rapid development of nanotechnology, potential applications of nanomaterials in medicine have been widely researched in recent years. Nanomaterials themselves can be used as image agents or therapeutic drugs, and for drug and gene delivery, biological devices, nanoelectronic biosensors or molecular nanotechnology. As the composition, morphology, chemical properties, implant sites as well as potential applications become more and more complex, human biosafety of nanomaterials for clinical use has become a major concern. If nanoparticles accumulate in the human body or interact with the body molecules or chemical components, health risks may also occur. Accordingly, the unique chemical and physical properties, potential applications in medical fields, as well as human biosafety in clinical trials are reviewed in this study. Finally, this article tries to give some suggestions for future work in nanomedicine research. Copyright © 2017 John Wiley & Sons, Ltd.

Review: Antimicrobial efficacy validation using in vitro and in vivo testing methods

Pre-clinical antimicrobial validation testing for single and combination products, and parameters that should be considered when testing the antimicrobial performance of a medical device, are discussed. Guidance is provided on key elements required for in vitro and in vivo antimicrobial validation, including validation of microbial growth, microbial recovery, neutralization, and antimicrobial activity. An important consideration, both in terms of practicality and economics, is designing in vitro studies that bridge to in vivo testing: A representative in vitro model is used to generate data on many clinically relevant microorganisms, and then one microorganism is selected for use in in vivo testing. If the in vivo results correlate to the in vitro results, it can reasonably be extrapolated that the same would be true for the remaining microorganisms tested in vitro. Thus, the selection of relevant in vitro models for testing is critical for successful antimicrobial validation testing.

Interfacial Stacks of Polymeric Nanofilms on Soft Biological Surfaces that Release Multiple Agents

We report a general and facile method that permits the transfer (stacking) of multiple independently fabricated and nanoscopically thin polymeric films, each containing a distinct bioactive agent, onto soft biomedically relevant surfaces (e.g., collagen-based wound dressings). By using polyelectrolyte multilayer films (PEMs) formed from poly(allyl amine hydrochloride) and poly(acrylic acid) as representative polymeric nanofilms and micrometer-thick water-soluble poly(vinyl alcohol) sacrificial films to stack the PEMs, we demonstrate that it is possible to create stacked polymeric constructs containing multiple bioactive agents (e.g., antimicrobial and antibiofilm agents) on soft and chemically complex surfaces onto which PEMs cannot be routinely transferred by stamping. We illustrate the characteristics and merits of the approach by fabricating stacks of Ga³⁺ (antibiofilm agent)- and Ag⁺ (antimicrobial agent)-loaded PEMs as prototypical examples of agent-containing PEMs and demonstrate that the stacked PEMs incorporate precise loadings of the agents and provide flexibility in terms of tuning release rates. Specifically, we show that simultaneous release of Ga³⁺ and Ag⁺ from the stacked PEMs on collagen-based wound dressings can lead to synergistic effects on bacteria, killing and dispersing biofilms formed by Pseudomonas aeruginosa (two strains: ATCC 27853 and MPAO1) at sufficiently low loadings of agents such that cytotoxic effects on mammalian cells are avoided. The approach is general (a wide range of bioactive agents other than Ga³⁺ and Ag⁺ can be incorporated into PEMs), and the modular nature of the approach potentially allows end-user functionalization of soft biological surfaces for programmed release of multiple bioactive agents.

Efficacy of silver coated surgical sutures on bacterial contamination, cellular response and wound healing

The resistance demonstrated by many microorganisms towards conventional antibiotics has stimulated the interest in alternative antimicrobial agents and in novel approaches for prevention of infections. Silver, a natural braod-spectrum antimicrobial agent known since antiquity, has been widely employed in biomedical field due to its recognized antibacterial, antifungal and antiviral properties. In this work, antibacterial silver coatings were deposited on absorbable surgical sutures through the in situ photo-chemical deposition of silver clusters. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and thermo-gravimetric analysis (TGA) were performed in order to investigate the presence and distribution of the silver clusters on the substrate. The amounts of silver deposited and released by the silver treated sutures were calculated through Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS), and the results were related to the biodegradation of the material. The microbiological properties and the potential cytotoxicity of the silver-treated sutures were investigated in relation with hydrolysis experiments, in order to determine the effect of the degradation on antibacterial properties and biocompatibility.

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.

Electron transfer driven highly valent silver for chronic wound treatment

This paper shows that reducing the dose of silver, additionally conferring electron transfer potential, could simultaneously achieve good biocompatibility and strong bactericidal ability without introducing extra chemical residuals for chronic wound treatment.

Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles

The utilization of various plant resources for the bio synthesis of metallic nano particles is called green technology and it does not utilize any harmful protocols. Present study focuses on the green synthesis of ZnO nano particles by Zinc Carbonate and utilizing the bio-components of powder extract of dry ginger rhizome (Zingiber officinale). The ZnO nano crystallites of average size range of 23-26 nm have been synthesized by rapid, simple and eco friendly method. Zinc oxide nano particles were characterized by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX). FTIR spectra confirmed the adsorption of surfactant molecules at the surface of ZnO nanoparticles and the presence of ZnO bonding. Antimicrobial activity of ZnO nano particles was done by well diffusion method against pathogenic organisms like Klebsiella pneumonia, Staphylococcus aureus and Candida albicans and Penicillium notatum. It is observed that the ZnO synthesized in the process has the efficient antimicrobial activity.

Characterization of green synthesized nano-formulation (ZnO-A. vera) and their antibacterial activity against pathogens

The application of nanotechnology in medicine has recently been a breakthrough in therapeutic drugs formulation. This paper presents the structural and optical characterization of a new green nano-formulation (ZnO-Aloe vera) with considerable antibacterial activity against pathogenic bacteria. Its particle structure, size and morphology were characterized by XRD, TEM and SEM. And optical absorption spectra and photoluminescence were measured synchronously. Their antibacterial activity against Escherichia coli and Staphylococcus aureus was also investigated using thermokinetic profiling and agar well diffusion method. The nano-formulation is spherical shape and hexagonal with a particle size ranging from 25 to 65 nm as well as an increased crystallite size of 49 nm. For antibacterial activity, the maximum inhibition zones of ZnO and ZnO+A. vera are 18.33 and 26.45 mm for E. coli, 22.11 and 28.12 mm for S. aureus (p<0.05). Considering Pmax, Qt and k, ZnO+A. vera nano-formulation has a significant (p < 0.05) antibacterial effect against S. aureus almost at all concentration and against E. coli at 15 and 25mg/L. ZnO+A. vera nano-formulation is much more toxic against S. aureus than E. coli, with an IC50 of 13.12 mg/L and 21.31 mg/L, respectively. The overall results reveal that the ZnO-A. vera nano-formulation has good surface energy, crystallinity, transmission, and enriched antibacterial activities. Their antibacterial properties are possibly relevant to particle size, microstructural ionization, the crystal formation and the Gram property of pathogens. This ZnO-A. vera nano-formulation could be utilized effectively as a spectral and significant antibacterial agent for pathogens in future medical and environmental concerns.

Green synthesis of ZnO nanoparticles using Solanum nigrum leaf extract and their antibacterial activity

In the present investigation, we have described the green biosynthesis of ZnO nanoparticles (NPs) by using Solanum nigrum as capping agent. The functionalization of ZnO particles through S. nigrum leaf extract mediated bioreduction of ZnO was investigated through UV-Vis DRS, photoluminescence (PL), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), thermal gravimetric-differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS) and antibacterial activities. UV-Vis-DRS studies revealed that the indirect band gap 3.38 eV and photoluminescence study reveals the blue emission at 402, 447, 469 and 483 nm and the green emission at 529 nm respectively. In addition, the synthesized NPs are wurtzite hexagonal structure with an average grain size lies between 20 and 30 nm were found from XRD analysis. Further, FT-IR spectra revealed the functional groups and the presence of protein as the stabilizing agent for surrounding the ZnO NPs. The diameter of the NPs in the range of 20-30 nm was found from FE-SEM study. TEM analysis was investigated the ZnO NPs as a quasi-spherical in shape and their diameter at around 29.79 nm. Finally, the current study has clearly demonstrated that the particle size variations and surface area to volume ratios of ZnO NPs are responsible for significant higher antibacterial activities. Further, the present investigation suggests that ZnO NPs has the potential applications for various medical and industrial fields so, that the investigation is so useful and helpful to the scientific communities.

Design, optical and antimicrobial properties of extremely thin alumina films colored with silver nanospecies

Extremely thin alumina films gold-colored by silver nm-scaled species possess a low refractive index and antimicrobial efficiency.

Effect of light on physicochemical and biological properties of nanocrystalline silver dressings

The purpose of this study was to characterize the interactive effects of light and aging on physicochemical properties and antimicrobial activity of nanocrystalline silver wound dressings Acticoat that might find their way into the environment.

Pyocyanin production by Pseudomonas aeruginosa confers resistance to ionic silver

Silver in its ionic form (Ag+), but not the bulk metal (Ag0), is toxic to microbial life forms and has been used for many years in the treatment of wound infections. The prevalence of bacterial resistance to silver is considered low due to the nonspecific nature of its toxicity. However, the recent increased use of silver as an antimicrobial agent for medical, consumer, and industrial products has raised concern that widespread silver resistance may emerge. Pseudomonas aeruginosa is a common pathogen that produces pyocyanin, a redox toxin and a reductant for molecular oxygen and ferric (Fe3+) ions. The objective of this study was to determine whether pyocyanin reduces Ag+ to Ag0, which may contribute to silver resistance due to lower bioavailability of the cation. Using surface plasmon resonance spectroscopy and scanning electron microscopy, pyocyanin was confirmed to be a reductant for Ag+, forming Ag0 nanoparticles and reducing the bioavailability of free Ag+ by >95% within minutes. Similarly, a pyocyanin-producing strain of P. aeruginosa (PA14) reduced Ag+ but not a pyocyanin-deficient (ΔphzM) strain of the bacterium. Challenge of each strain with Ag+ (as AgNO3) gave MICs of 20 and 5 μg/ml for the PA14 and ΔphzM strains, respectively. Removal of pyocyanin from the medium strain PA14 was grown in or its addition to the medium that ΔphzM mutant was grown in gave MICs of 5 and 20 μg/ml, respectively. Clinical isolates demonstrated similar pyocyanin-dependent resistance to Ag+. We conclude that pseudomonal silver resistance exists independently of previously recognized intracellular mechanisms and may be more prevalent than previously considered.

Reduction in wound bioburden using a silver-loaded dissolvable microfilm construct

Silver is a widely used antimicrobial agent, yet, when impregnated in macroscopic dressings, it stains wounds, can lead to tissue toxicity, and can inhibit healing. Recently, polymeric nanofilms containing silver nanoparticles were reported to exhibit antimicrobial activity at loadings and release rates of silver that are 100× lower than conventional dressings. Here, fabrication of composite microfilm constructs that provide a facile way to transfer the silver-loaded polymeric nanofilms onto wounds in vivo is reported. The construct is fabricated from a silver nanoparticle-loaded polymeric nanofilm that is laminated with a micrometer-thick-soluble film of polyvinylalcohol (PVA). When placed on a moist wound, the PVA dissolves, leaving the silver-loaded nanofilm immobilized on the wound-bed. In vitro, the immobilized nanofilms release <1 μg cm(-2) d(-1) of silver over 30 d from skin dermis and they kill 5 log10 CFUs of Staphylococcus aureus in 24 h. In mice, wounds inoculated with 10(5) CFU S. aureus presented up to 3 log10 less bacterial burden when treated with silver/nanofilms for 3 d, as compared to unmodified wounds. In uncontaminated wounds, silver/nanofilms allow normal and complete wound closure by re-epithelialization. Dissolvable microfilm constructs may overcome key limitations associated with current uses of silver in wound healing.

Nanosilver particles in medical applications: synthesis, performance, and toxicity

Nanosilver particles (NSPs), are among the most attractive nanomaterials, and have been widely used in a range of biomedical applications, including diagnosis, treatment, drug delivery, medical device coating, and for personal health care. With the increasing application of NSPs in medical contexts, it is becoming necessary for a better understanding of the mechanisms of NSPs' biological interactions and their potential toxicity. In this review, we first introduce the synthesis routes of NSPs, including physical, chemical, and biological or green synthesis. Then the unique physiochemical properties of NSPs, such as antibacterial, antifungal, antiviral, and anti-inflammatory activity, are discussed in detail. Further, some recent applications of NSPs in prevention, diagnosis, and treatment in medical fields are described. Finally, potential toxicology considerations of NSPs, both in vitro and in vivo, are also addressed.

Nanosilver particles in medical applications: synthesis, performance, and toxicity

Nanosilver particles (NSPs), are among the most attractive nanomaterials, and have been widely used in a range of biomedical applications, including diagnosis, treatment, drug delivery, medical device coating, and for personal health care. With the increasing application of NSPs in medical contexts, it is becoming necessary for a better understanding of the mechanisms of NSPs' biological interactions and their potential toxicity. In this review, we first introduce the synthesis routes of NSPs, including physical, chemical, and biological or green synthesis. Then the unique physiochemical properties of NSPs, such as antibacterial, antifungal, antiviral, and anti-inflammatory activity, are discussed in detail. Further, some recent applications of NSPs in prevention, diagnosis, and treatment in medical fields are described. Finally, potential toxicology considerations of NSPs, both in vitro and in vivo, are also addressed.

Cytotoxicity testing of silver-containing burn treatments using primary and immortal skin cells

A novel burn wound hydrogel dressing has been previously developed which is composed of 2-acrylamido-2-methylpropane sulfonic acid sodium salt with silver nanoparticles (silver AMPS). This study compared the cytotoxicity of this dressing to the commercially available silver products; Acticoat™, PolyMem Silver(®) and Flamazine™ cream. Human keratinocytes (HaCaT and primary HEK) and normal human fibroblasts (NHF) were exposed to dressings incubated on Nunc™ polycarbonate inserts for 24, 48 and 72h. Four different cytotoxicity assays were performed including; Trypan Blue cell count, MTT, Celltiter-Blue™ and Toluidine Blue surface area assays. The results were expressed as relative cell viability compared to an untreated control. The cytotoxic effects of Acticoat™ and Flamazine™ cream were dependent on exposure time and cell type. After 24h exposure, Acticoat™ and Flamazine™ cream were toxic to all tested cell lines. Surprisingly, HaCaTs treated with Acticoat™ and Flamazine™ had an improved ability to survive at 48 and 72h while HEKs and NHFs had no improvement in survival with any treatment. The novel silver hydrogel and PolyMem Silver(®) showed low cytotoxicity to all tested cell lines at every time interval and these results support the possibility of using the novel silver hydrogel as a burn wound dressing. Researchers who rely on HaCaT cells as an accurate keratinocyte model should be aware that they can respond differently to primary skin cells.

A review of the biomaterials technologies for infection-resistant surfaces

Anti-infective biomaterials need to be tailored according to the specific clinical application. All their properties have to be tuned to achieve the best anti-infective performance together with safe biocompatibility and appropriate tissue interactions. Innovative technologies are developing new biomaterials and surfaces endowed with anti-infective properties, relying either on antifouling, or bactericidal, or antibiofilm activities. This review aims at thoroughly surveying the numerous classes of antibacterial biomaterials and the underlying strategies behind them. Bacteria repelling and antiadhesive surfaces, materials with intrinsic antibacterial properties, antibacterial coatings, nanostructured materials, and molecules interfering with bacterial biofilm are considered. Among the new strategies, the use of phages or of antisense peptide nucleic acids are discussed, as well as the possibility to modulate the local immune response by active cytokines. Overall, there is a wealth of technical solutions to contrast the establishment of an implant infection. Many of them exhibit a great potential in preclinical models. The lack of well-structured prospective multicenter clinical trials hinders the achievement of conclusive data on the efficacy and comparative performance of anti-infective biomaterials.

Versatile photochemical surface modification of biopolyester microfibrous scaffolds with photogenerated silver nanoparticles for antibacterial activity

A straightforward and versatile method for immobilizing macromolecules and silver nanoparticles on the surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) electrospun fibers is developed with the objective of designing a new functional material having significant antibacterial activity. The approach relies on a two-step procedure: UV photografting of poly(methacrylic acid) (PMAA) on the surface of PHBHV fibers according to a "grafting from" method, and complexation of in situ photogenerated silver nanoparticles (Ag NPs) by carboxyl groups from tethered PMAA chains. The photografting process is conducted through a photoinduced free-radical process employing a ketone-based photoinitiator in aqueous medium. Under appropriate conditions, the photogenerated radicals abstract hydrogen atoms from the PHBHV backbone, thus initiating the UV-mediated photopolymerization of MAA from the PHBHV microfibrous surface. The photochemical mechanism of the ketone photolysis is entirely described by the electron spin resonance/spin-trapping technique, and the modified PHBHV microfibrous scaffold is extensively characterized by ATR-FTIR spectroscopy, water contact-angle measurements, and mercury intrusion porosimetry. In a second step, the in situ synthesis of Ag NPs within the microfibrous scaffold is implemented by photoreduction reaction in the presence of both a silver precursor and a photosensitizer. The photoinduced formation of Ag NPs is confirmed by UV spectrophotometry and XPS analysis. SEM and TEM experiments confirm the formation and dispersion of Ag NPs on the surface of the modified fibers. Finally, a primary investigation is conducted to support the antibacterial activity of the new functionalized biomaterial against Staphylococcus aureus and Escherichia coli.

Antibacterial efficacy of silver-impregnated polyelectrolyte multilayers immobilized on a biological dressing in a murine wound infection model

OBJECTIVE

To investigate the antibacterial effect of augmenting a biological dressing with polymer films containing silver nanoparticles.

BACKGROUND

Biological dressings, such as Biobrane, are commonly used for treating partial-thickness wounds and burn injuries. Biological dressings have several advantages over traditional wound dressings. However, as many as 19% of wounds treated with Biobrane become infected, and, once infected, the Biobrane must be removed and a traditional dressing approach should be employed. Silver is a commonly used antimicrobial in wound care products, but current technology uses cytotoxic concentrations of silver in these dressings. We have developed a novel and facile technology that allows immobilization of bioactive molecules on the surfaces of soft materials, demonstrated here by augmentation of Biobrane with nanoparticulate silver. Surfaces modified with nanometer-thick polyelectrolyte multilayers (PEMs) impregnated with silver nanoparticles have been shown previously to result in in vitro antibacterial activity against Staphylococcus epidermidis at loadings of silver that are noncytotoxic.

METHODS

We demonstrated that silver-impregnated PEMs can be nondestructively immobilized onto the surface of Biobrane (Biobrane-Ag) and determined the in vitro antibacterial activity of Biobrane-Ag with Staphylococcus aureus. In this study, we used an in vivo wound infection model in mice induced by topical inoculation of S aureus onto full-thickness 6-mm diameter wounds. After 72 hours, bacterial quantification was performed.

RESULTS

Wounds treated with Biobrane-Ag had significantly (P < 0.001) fewer colony-forming units than wounds treated with unmodified Biobrane (more than 4 log10 difference).

CONCLUSIONS

The results of our study indicate that immobilizing silver-impregnated PEMs on the wound-contact surface of Biobrane significantly reduces bacterial bioburden in full-thickness murine skin wounds. Further research will investigate whether this construct can be considered for human use.