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Antibiotics
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Silver-Based Antimicrobials
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Silver-Based Antimicrobials

A special issue of Antibiotics (ISSN 2079-6382).

Deadline for manuscript submissions: closed (30 June 2018) | Viewed by 109815

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Raymond J. Turner

E-Mail Website
Guest Editor
Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
Interests: metal based antimicrobials; resistance mechanisms; biofilms; antimicrobial properties; bioremediation; metal nanomaterials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Long before the discovery of antibiotics, silver had been used to help keep water fresh on ships of passage, and alchemists used it to treat wounds to improve healing and to heal contagious diseases, which led silver (and other metals) to acquire a reputation of having antimicrobial properties. However, with the introduction of antibiotics, the use of silver as an antibacterial agent drastically decreased. Driven by the great challenges that the increased prevalence of drug-resistant pathogens have posed as we move into the antibiotic resistance era, the interest in employing silver to combat bacterial infections has recently been revived. Research to date suggests that silver has superior antibacterial efficacy over other medicinally relevant metals.

In this Special Issue of “Silver-Based Antimicrobials”, we will highlight research findings that cover topics centering on silver as antibiotic, antiseptic, and surface coating for infection control. It will involve but be not limited to:

  • mechanism(s) of resistance
  • mechanism(s) of toxicity
  • mechanisms of action
  • delivery vehicles
  • specificity
  • cytotoxicity
  • hemolytic activity
  • binding of silver to biomolecules
  • synergies with other antimicrobials
  • novel formulations
  • nanoparticles
  • novel coatings
  • agriculture and animal use
  • waste issues

Despite its well-known antimicrobial properties, silver’s mechanisms of action—whose diversity contributes to the rarely reported resistance—have not been completely elucidated. Additionally, surprisingly little is known of its toxicology to humans and other animals. Therefore, we are also particularly interested in discoveries of its mechanisms of action in this Special Issue.

Prof. Dr. Raymond J. Turner
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Antibiotics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (17 papers)

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Editorial

Jump to: Research, Review

2 pages, 144 KiB  
Editorial
Is Silver the Ultimate Antimicrobial Bullet?
by Raymond J Turner
Antibiotics 2018, 7(4), 112; https://doi.org/10.3390/antibiotics7040112 - 19 Dec 2018
Cited by 8 | Viewed by 2815
Abstract
The use of metal compounds as antimicrobial agents has been around since antiquity, only to be replaced by the introduction of organic antibiotics and antiseptics in the mid-20th century. [...] Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)

Research

Jump to: Editorial, Review

12 pages, 2079 KiB  
Article
Silver Nanoparticle Conjugation-Enhanced Antibacterial Efficacy of Clinically Approved Drugs Cephradine and Vildagliptin
by Abdulkader Masri, Ayaz Anwar, Dania Ahmed, Ruqaiyyah Bano Siddiqui, Muhammad Raza Shah and Naveed Ahmed Khan
Antibiotics 2018, 7(4), 100; https://doi.org/10.3390/antibiotics7040100 - 15 Nov 2018
Cited by 57 | Viewed by 5979
Abstract
This paper sets out to determine whether silver nanoparticles conjugation enhance the antibacterial efficacy of clinically approved drugs. Silver conjugated Cephradine and Vildagliptin were synthesized and thoroughly characterized by ultraviolet visible spectrophotometry (UV-vis), Fourier transform infrared (FT-IR) spectroscopic methods, atomic force microscopy (AFM), [...] Read more.
This paper sets out to determine whether silver nanoparticles conjugation enhance the antibacterial efficacy of clinically approved drugs. Silver conjugated Cephradine and Vildagliptin were synthesized and thoroughly characterized by ultraviolet visible spectrophotometry (UV-vis), Fourier transform infrared (FT-IR) spectroscopic methods, atomic force microscopy (AFM), and dynamic light scattering (DLS) analysis. Using antibacterial assays, the effects of drugs alone and drugs-conjugated with silver nanoparticles were tested against a variety of Gram-negative and Gram-positive bacteria including neuropathogenic Escherichia coli K1, Pseudomonas aeruginosa, Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus (MRSA), Bacillus cereus and Streptococcus pyogenes. Cytopathogenicity assays were performed to determine whether pretreatment of bacteria with drugs inhibit bacterial-mediated host cell cytotoxicity. The UV-vis spectra of both silver-drug nanoconjugates showed a characteristic surface plasmon resonance band in the range of 400–450 nm. AFM further confirmed the morphology of nanoparticles and revealed the formation of spherical nanoparticles with size distribution of 30–80 nm. FT-IR analysis demonstrated the involvement of Hydroxyl groups in both drugs in the stabilization of silver nanoparticles. Antibacterial assays showed that silver nanoparticle conjugation enhanced antibacterial potential of both Cephradine and Vildagliptin compared to the drugs alone. Pretreatment of bacteria with drugs inhibited E. coli K1-mediated host cell cytotoxicity. In summary, conjugation with silver nanoparticle enhanced antibacterial effects of clinically approved Cephradine. These findings suggest that modifying and/or repurposing clinically approved drugs using nanotechnology is a feasible approach in our search for effective antibacterial molecules. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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10 pages, 709 KiB  
Article
Microbiome Analysis of Biofilms of Silver Nanoparticle-Dispersed Silane-Based Coated Carbon Steel Using a Next-Generation Sequencing Technique
by Akiko Ogawa, Keito Takakura, Katsuhiko Sano, Hideyuki Kanematsu, Takehiko Yamano, Toshikazu Saishin and Satoshi Terada
Antibiotics 2018, 7(4), 91; https://doi.org/10.3390/antibiotics7040091 - 22 Oct 2018
Cited by 4 | Viewed by 3442
Abstract
Previously, we demonstrated that silver nanoparticle-dispersed silane-based coating could inhibit biofilm formation in conditions where seawater was used as a bacterial source and circulated in a closed laboratory biofilm reactor. However, it is still unclear whether the microbiome of a biofilm of silver [...] Read more.
Previously, we demonstrated that silver nanoparticle-dispersed silane-based coating could inhibit biofilm formation in conditions where seawater was used as a bacterial source and circulated in a closed laboratory biofilm reactor. However, it is still unclear whether the microbiome of a biofilm of silver nanoparticle-dispersed silane-based coating samples (Ag) differs from that of a biofilm of non-dispersed silane-based coating samples (Non-Ag). This study aimed to perform a microbiome analysis of the biofilms grown on the aforementioned coatings using a next-generation sequencing (NGS) technique. For this, a biofilm formation test was conducted by allowing seawater to flow through a closed laboratory biofilm reactor; subsequently, DNAs extracted from the biofilms of Ag and Non-Ag were used to prepare 16S rRNA amplicon libraries to analyze the microbiomes by NGS. Results of the operational taxonomy unit indicated that the biofilms of Non-Ag and Ag comprised one and no phyla of archaea, respectively, whereas Proteobacteria was the dominant phylum for both biofilms. Additionally, in both biofilms, Non-Ag and Ag, Marinomonas was the primary bacterial group involved in early stage biofilm formation, whereas Anaerospora was primarily involved in late-stage biofilm formation. These results indicate that silver nanoparticles will be unrelated to the bacterial composition of biofilms on the surface of silane-based coatings, while they control biofilm formation there. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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18 pages, 3414 KiB  
Article
Plasmon Resonance of Silver Nanoparticles as a Method of Increasing Their Antibacterial Action
by Alexander Yu. Vasil’kov, Ruslan I. Dovnar, Siarhei M. Smotryn, Nikolai N. Iaskevich and Alexander V. Naumkin
Antibiotics 2018, 7(3), 80; https://doi.org/10.3390/antibiotics7030080 - 22 Aug 2018
Cited by 49 | Viewed by 4150
Abstract
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, [...] Read more.
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. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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12 pages, 1497 KiB  
Article
Silver Nanoparticles and Polyphenol Inclusion Compounds Composites for Phytophthora cinnamomi Mycelial Growth Inhibition
by Petruta Mihaela Matei, Jesús Martín-Gil, Beatrice Michaela Iacomi, Eduardo Pérez-Lebeña, María Teresa Barrio-Arredondo and Pablo Martín-Ramos
Antibiotics 2018, 7(3), 76; https://doi.org/10.3390/antibiotics7030076 - 16 Aug 2018
Cited by 17 | Viewed by 5586
Abstract
Phytophthora cinnamomi, responsible for “root rot” or “dieback” plant disease, causes a significant amount of economic and environmental impact. In this work, the fungicide action of nanocomposites based on silver nanoparticles and polyphenol inclusion compounds, which feature enhanced bioavailability and water solubility, [...] Read more.
Phytophthora cinnamomi, responsible for “root rot” or “dieback” plant disease, causes a significant amount of economic and environmental impact. In this work, the fungicide action of nanocomposites based on silver nanoparticles and polyphenol inclusion compounds, which feature enhanced bioavailability and water solubility, was assayed for the control of this soil-borne water mold. Inclusion compounds were prepared by an aqueous two-phase system separation method through extraction, either in an hydroalcoholic solution with chitosan oligomers (COS) or in a choline chloride:urea:glycerol deep eutectic solvent (DES). The new inclusion compounds were synthesized from stevioside and various polyphenols (gallic acid, silymarin, ferulic acid and curcumin), in a [6:1] ratio in the COS medium and in a [3:1] ratio in the DES medium, respectively. Their in vitro response against Phytophthora cinnamomi isolate MYC43 (at concentrations of 125, 250 and 500 µg·mL−1) was tested, which found a significant mycelial growth inhibition, particularly high for the composites prepared using DES. Therefore, these nanocomposites hold promise as an alternative to fosetyl-Al and metalaxyl conventional systemic fungicides. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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10 pages, 2554 KiB  
Article
Microwave-Assisted Green Synthesis of Silver Nanoparticles Using Juglans regia Leaf Extract and Evaluation of Their Physico-Chemical and Antibacterial Properties
by Mahsa Eshghi, Hamideh Vaghari, Yahya Najian, Mohammad Javad Najian, Hoda Jafarizadeh-Malmiri and Aydin Berenjian
Antibiotics 2018, 7(3), 68; https://doi.org/10.3390/antibiotics7030068 - 30 Jul 2018
Cited by 19 | Viewed by 4823
Abstract
Silver nanoparticles (Ag NPs) were synthesized using Juglans regia (J. regia) leaf extract, as both reducing and stabilizing agents through microwave irradiation method. The effects of a 1% (w/v) amount of leaf extract (0.1–0.9 mL) and an [...] Read more.
Silver nanoparticles (Ag NPs) were synthesized using Juglans regia (J. regia) leaf extract, as both reducing and stabilizing agents through microwave irradiation method. The effects of a 1% (w/v) amount of leaf extract (0.1–0.9 mL) and an amount of 1 mM AgNO3 solution (15–25 mL) on the broad emission peak (λmax) and concentration of the synthesized Ag NPs solution were investigated using response surface methodology (RSM). Fourier transform infrared analysis indicated the main functional groups existing in the J. regia leaf extract. Dynamic light scattering, UV-Vis spectroscopy and transmission electron microscopy were used to characterize the synthesized Ag NPs. Fabricated Ag NPs with the mean particle size and polydispersity index and maximum concentration and zeta potential of 168 nm, 0.419, 135.16 ppm and −15.6 mV, respectively, were obtained using 0.1 mL of J. regia leaf extract and 15 mL of AgNO3. The antibacterial activity of the fabricated Ag NPs was assessed against both Gram negative (Escherichia coli) and positive (Staphylococcus aureus) bacteria and was found to possess high bactericidal effects. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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13 pages, 2869 KiB  
Article
Tunable Silver-Functionalized Porous Frameworks for Antibacterial Applications
by Mark A. Isaacs, Brunella Barbero, Lee J. Durndell, Anthony C. Hilton, Luca Olivi, Christopher M. A. Parlett, Karen Wilson and Adam F. Lee
Antibiotics 2018, 7(3), 55; https://doi.org/10.3390/antibiotics7030055 - 03 Jul 2018
Cited by 8 | Viewed by 5337
Abstract
Healthcare-associated infections and the rise of drug-resistant bacteria pose significant challenges to existing antibiotic therapies. Silver nanocomposites are a promising solution to the current crisis, however their therapeutic application requires improved understanding of underpinning structure-function relationships. A family of chemically and structurally modified [...] Read more.
Healthcare-associated infections and the rise of drug-resistant bacteria pose significant challenges to existing antibiotic therapies. Silver nanocomposites are a promising solution to the current crisis, however their therapeutic application requires improved understanding of underpinning structure-function relationships. A family of chemically and structurally modified mesoporous SBA-15 silicas were synthesized as porous host matrices to tune the physicochemical properties of silver nanoparticles. Physicochemical characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES) and porosimetry demonstrate that functionalization by a titania monolayer and the incorporation of macroporosity both increase silver nanoparticle dispersion throughout the silica matrix, thereby promoting Ag2CO3 formation and the release of ionic silver in simulated tissue fluid. The Ag2CO3 concentration within functionalized porous architectures is a strong predictor for antibacterial efficacy against a broad spectrum of pathogens, including C. difficile and methicillin-resistant Staphylococcus aureus (MRSA). Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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11 pages, 2711 KiB  
Article
Nanosynthesis of Silver-Calcium Glycerophosphate: Promising Association against Oral Pathogens
by Gabriela Lopes Fernandes, Alberto Carlos Botazzo Delbem, Jackeline Gallo Do Amaral, Luiz Fernando Gorup, Renan Aparecido Fernandes, Francisco Nunes De Souza Neto, José Antonio Santos Souza, Douglas Roberto Monteiro, Alessandra Marçal Agostinho Hunt, Emerson Rodrigues Camargo and Debora Barros Barbosa
Antibiotics 2018, 7(3), 52; https://doi.org/10.3390/antibiotics7030052 - 27 Jun 2018
Cited by 23 | Viewed by 4644
Abstract
Nanobiomaterials combining remineralization and antimicrobial abilities would bring important benefits to control dental caries. This study aimed to produce nanocompounds containing calcium glycerophosphate (CaGP) and silver nanoparticles (AgNP) by varying the reducing agent of silver nitrate (sodium borohydride (B) or sodium citrate (C)), [...] Read more.
Nanobiomaterials combining remineralization and antimicrobial abilities would bring important benefits to control dental caries. This study aimed to produce nanocompounds containing calcium glycerophosphate (CaGP) and silver nanoparticles (AgNP) by varying the reducing agent of silver nitrate (sodium borohydride (B) or sodium citrate (C)), the concentration of silver (1% or 10%), and the CaGP forms (nano or commercial), and analyze its characterization and antimicrobial activity against ATCC Candida albicans (10231) and Streptococcus mutans (25175) by the microdilution method. Controls of AgNP were produced and silver ions (Ag+) were quantified in all of the samples. X-ray diffraction, UV-Vis, and scanning electron microscopy (SEM) analysis demonstrated AgNP associated with CaGP. Ag+ ions were considerably higher in AgCaGP/C. C. albicans was susceptible to nanocompounds produced with both reducing agents, regardless of Ag concentration and CaGP form, being Ag10%CaGP-N/C the most effective compound (19.5–39.0 µg Ag mL−1). While for S. mutans, the effectiveness was observed only for AgCaGP reduced by citrate, also presenting Ag10%CaGP-N the highest effectiveness (156.2–312.5 µg Ag mL−1). Notably, CaGP enhanced the silver antimicrobial potential in about two- and eight-fold against C. albicans and S. mutans when compared with the AgNP controls (from 7.8 to 3.9 and from 250 to 31.2 µg Ag mL−1, respectively). The synthesis that was used in this study promoted the formation of AgNP associated with CaGP, and although the use of sodium borohydride (B) resulted in a pronounced reduction of Ag+, the composite AgCaGP/B was less effective against the microorganisms that were tested. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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14 pages, 2946 KiB  
Article
Antimicrobial Potential and Cytotoxicity of Silver Nanoparticles Phytosynthesized by Pomegranate Peel Extract
by Renan Aparecido Fernandes, Andresa Aparecida Berretta, Elina Cassia Torres, Andrei Felipe Moreira Buszinski, Gabriela Lopes Fernandes, Carla Corrêa Mendes-Gouvêa, Francisco Nunes De Souza-Neto, Luiz Fernando Gorup, Emerson Rodrigues De Camargo and Debora Barros Barbosa
Antibiotics 2018, 7(3), 51; https://doi.org/10.3390/antibiotics7030051 - 26 Jun 2018
Cited by 25 | Viewed by 5115
Abstract
The phytosynthesis of metal nanoparticles is nowadays attracting the increased attention of researchers and is much needed given the worldwide matter related to environmental contamination. The antimicrobial activity of colloidal and spray formulation of silver nanoparticles (AgNPs) synthesized by pomegranate peel extract against [...] Read more.
The phytosynthesis of metal nanoparticles is nowadays attracting the increased attention of researchers and is much needed given the worldwide matter related to environmental contamination. The antimicrobial activity of colloidal and spray formulation of silver nanoparticles (AgNPs) synthesized by pomegranate peel extract against Candida albicans and Staphylococcus aureus, and their cytotoxicity in mammalian cells were tested in the present study. Dry matter, pH, total phenolics, and ellagic acid in the extract were determined. Then, AgNPs were phytosynthesized and characterized by X-ray diffraction, electron transmission microscopy, dynamic light scattering, zeta potential, and Ag+ dosage. Spray formulations and respective chemical-AgNP controls were prepared and tested. The peel extract reduced more than 99% of Ag+, and produced nanoparticles with irregular forms and an 89-nm mean size. All AgNP presented antimicrobial activity, and the spray formulation of green-AgNP increased by 255 and 4 times the effectiveness against S. aureus and C. albicans, respectively. The cytotoxicity of colloidal and spray green-AgNP was expressively lower than the respective chemical controls. Pomegranate peel extract produced stable AgNP with antimicrobial action and low cytotoxicity, stimulating its use in the biomedical field. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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13 pages, 2168 KiB  
Article
In Vitro Synergism of Silver Nanoparticles with Antibiotics as an Alternative Treatment in Multiresistant Uropathogens
by Montserrat Lopez-Carrizales, Karla Itzel Velasco, Claudia Castillo, Andrés Flores, Martín Magaña, Gabriel Alejandro Martinez-Castanon and Fidel Martinez-Gutierrez
Antibiotics 2018, 7(2), 50; https://doi.org/10.3390/antibiotics7020050 - 19 Jun 2018
Cited by 57 | Viewed by 7191
Abstract
The increase in the prevalence of bacterial resistance to antibiotics has become one of the main health problems worldwide, thus threatening the era of antibiotics most frequently used in the treatment of infections. The need to develop new therapeutic strategies against multidrug resistant [...] Read more.
The increase in the prevalence of bacterial resistance to antibiotics has become one of the main health problems worldwide, thus threatening the era of antibiotics most frequently used in the treatment of infections. The need to develop new therapeutic strategies against multidrug resistant microorganisms, such as the combination of selected antimicrobials, can be considered as a suitable alternative. The in vitro activities of two groups of conventional antimicrobial agents alone and in combination with silver nanoparticles (AgNPs) were investigated against a set of ten multidrug resistant clinical isolate and two references strains by MIC assays and checkerboard testing, as well as their cytotoxicity, which was evaluated on human fibroblasts by MTT assay at the same concentration of the antimicrobial agents alone and in combination. Interesting results were achieved when the AgNPs and their combinations were characterized by Dynamic Light Scattering (DLS), Zeta Potential, Transmission Electron Microscopy (TEM), UV–visible spectroscopy and Fourier Transforms Infrared (FTIR) spectroscopy. The in vitro activities of ampicillin, in combination with AgNPs, against the 12 microorganisms showed one Synergy, seven Partial Synergy and four Additive effects, while the results with amikacin and AgNPs showed three Synergy, eight Partial Synergy and one Additive effects. The cytotoxic effect at these concentrations presented a statistically significant decrease of their cytotoxicity (p < 0.05). These results indicate that infections caused by multidrug resistant microorganisms could be treated using a synergistic combination of antimicrobial drugs and AgNPs. Further studies are necessary to evaluate the specific mechanisms of action, which could help predict undesirable off-target interactions, suggest ways of regulating a drug’s activity, and identify novel therapeutic agents in this health problem. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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15 pages, 1163 KiB  
Article
Toxicological Assessment of a Lignin Core Nanoparticle Doped with Silver as an Alternative to Conventional Silver Core Nanoparticles
by Cassandra E. Nix, Bryan J. Harper, Cathryn G. Conner, Alexander P. Richter, Orlin D. Velev and Stacey L. Harper
Antibiotics 2018, 7(2), 40; https://doi.org/10.3390/antibiotics7020040 - 04 May 2018
Cited by 14 | Viewed by 5392
Abstract
Elevated levels of silver in the environment are anticipated with an increase in silver nanoparticle (AgNP) production and use in consumer products. To potentially reduce the burden of silver ion release from conventional solid core AgNPs, a lignin-core particle doped with silver ions [...] Read more.
Elevated levels of silver in the environment are anticipated with an increase in silver nanoparticle (AgNP) production and use in consumer products. To potentially reduce the burden of silver ion release from conventional solid core AgNPs, a lignin-core particle doped with silver ions and surface-stabilized with a polycationic electrolyte layer was engineered. Our objective was to determine whether any of the formulation components elicit toxicological responses using embryonic zebrafish. Ionic silver and free surface stabilizer were the most toxic constituents, although when associated separately or together with the lignin core particles, the toxicity of the formulations decreased significantly. The overall toxicity of lignin formulations containing silver was similar to other studies on a silver mass basis, and led to a significantly higher prevalence of uninflated swim bladder and yolk sac edema. Comparative analysis of dialyzed samples which had leached their loosely bound Ag+, showed a significant increase in mortality immediately after dialysis, in addition to eliciting significant increases in types of sublethal responses relative to the freshly prepared non-dialyzed samples. ICP-OES/MS analysis indicated that silver ion release from the particle into solution was continuous, and the rate of release differed when the surface stabilizer was not present. Overall, our study indicates that the lignin core is an effective alternative to conventional solid core AgNPs for potentially reducing the burden of silver released into the environment from a variety of consumer products. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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Review

Jump to: Editorial, Research

15 pages, 8626 KiB  
Review
Antimicrobial Silver in Medicinal and Consumer Applications: A Patent Review of the Past Decade (2007–2017)
by Wilson Sim, Ross T. Barnard, M.A.T. Blaskovich and Zyta M. Ziora
Antibiotics 2018, 7(4), 93; https://doi.org/10.3390/antibiotics7040093 - 26 Oct 2018
Cited by 249 | Viewed by 13595
Abstract
The use of silver to control infections was common in ancient civilizations. In recent years, this material has resurfaced as a therapeutic option due to the increasing prevalence of bacterial resistance to antimicrobials. This renewed interest has prompted researchers to investigate how the [...] Read more.
The use of silver to control infections was common in ancient civilizations. In recent years, this material has resurfaced as a therapeutic option due to the increasing prevalence of bacterial resistance to antimicrobials. This renewed interest has prompted researchers to investigate how the antimicrobial properties of silver might be enhanced, thus broadening the possibilities for antimicrobial applications. This review presents a compilation of patented products utilizing any forms of silver for its bactericidal actions in the decade 2007–2017. It analyses the trends in patent applications related to different forms of silver and their use for antimicrobial purposes. Based on the retrospective view of registered patents, statements of prognosis are also presented with a view to heightening awareness of potential industrial and health care applications. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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10 pages, 3236 KiB  
Review
Silver and Antibiotic, New Facts to an Old Story
by Frédéric Barras, Laurent Aussel and Benjamin Ezraty
Antibiotics 2018, 7(3), 79; https://doi.org/10.3390/antibiotics7030079 - 22 Aug 2018
Cited by 69 | Viewed by 7537
Abstract
The therapeutic arsenal against bacterial infections is rapidly shrinking, as drug resistance spreads and pharmaceutical industry are struggling to produce new antibiotics. In this review we cover the efficacy of silver as an antibacterial agent. In particular we recall experimental evidences pointing to [...] Read more.
The therapeutic arsenal against bacterial infections is rapidly shrinking, as drug resistance spreads and pharmaceutical industry are struggling to produce new antibiotics. In this review we cover the efficacy of silver as an antibacterial agent. In particular we recall experimental evidences pointing to the multiple targets of silver, including DNA, proteins and small molecules, and we review the arguments for and against the hypothesis that silver acts by enhancing oxidative stress. We also review the recent use of silver as an adjuvant for antibiotics. Specifically, we discuss the state of our current understanding on the potentiating action of silver ions on aminoglycoside antibiotics. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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17 pages, 3302 KiB  
Review
State-of-the-Art, and Perspectives of, Silver/Plasma Polymer Antibacterial Nanocomposites
by Jiří Kratochvíl, Anna Kuzminova and Ondřej Kylián
Antibiotics 2018, 7(3), 78; https://doi.org/10.3390/antibiotics7030078 - 17 Aug 2018
Cited by 27 | Viewed by 5592
Abstract
Urgent need for innovative and effective antibacterial coatings in different fields seems to have triggered the development of numerous strategies for the production of such materials. As shown in this short overview, plasma based techniques arouse considerable attention that is connected with the [...] Read more.
Urgent need for innovative and effective antibacterial coatings in different fields seems to have triggered the development of numerous strategies for the production of such materials. As shown in this short overview, plasma based techniques arouse considerable attention that is connected with the possibility to use these techniques for the production of advanced antibacterial Ag/plasma polymer coatings with tailor-made functional properties. In addition, the plasma-based deposition is believed to be well-suited for the production of novel multi-functional or stimuli-responsive antibacterial films. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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24 pages, 1846 KiB  
Review
Biogenic Nanosilver against Multidrug-Resistant Bacteria (MDRB)
by Caio H. N. Barros, Stephanie Fulaz, Danijela Stanisic and Ljubica Tasic
Antibiotics 2018, 7(3), 69; https://doi.org/10.3390/antibiotics7030069 - 02 Aug 2018
Cited by 87 | Viewed by 9847
Abstract
Multidrug-resistant bacteria (MDRB) are extremely dangerous and bring a serious threat to health care systems as they can survive an attack from almost any drug. The bacteria’s adaptive way of living with the use of antimicrobials and antibiotics caused them to modify and [...] Read more.
Multidrug-resistant bacteria (MDRB) are extremely dangerous and bring a serious threat to health care systems as they can survive an attack from almost any drug. The bacteria’s adaptive way of living with the use of antimicrobials and antibiotics caused them to modify and prevail in hostile conditions by creating resistance to known antibiotics or their combinations. The emergence of nanomaterials as new antimicrobials introduces a new paradigm for antibiotic use in various fields. For example, silver nanoparticles (AgNPs) are the oldest nanomaterial used for bactericide and bacteriostatic purposes. However, for just a few decades these have been produced in a biogenic or bio-based fashion. This review brings the latest reports on biogenic AgNPs in the combat against MDRB. Some antimicrobial mechanisms and possible silver resistance traits acquired by bacteria are also presented. Hopefully, novel AgNPs-containing products might be designed against MDR bacterial infections. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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28 pages, 4904 KiB  
Review
The Pros and Cons of the Use of Laser Ablation Synthesis for the Production of Silver Nano-Antimicrobials
by Maria Chiara Sportelli, Margherita Izzi, Annalisa Volpe, Maurizio Clemente, Rosaria Anna Picca, Antonio Ancona, Pietro Mario Lugarà, Gerardo Palazzo and Nicola Cioffi
Antibiotics 2018, 7(3), 67; https://doi.org/10.3390/antibiotics7030067 - 28 Jul 2018
Cited by 109 | Viewed by 10538
Abstract
Silver nanoparticles (AgNPs) are well-known for their antimicrobial effects and several groups are proposing them as active agents to fight antimicrobial resistance. A wide variety of methods is available for nanoparticle synthesis, affording a broad spectrum of chemical and physical properties. In this [...] Read more.
Silver nanoparticles (AgNPs) are well-known for their antimicrobial effects and several groups are proposing them as active agents to fight antimicrobial resistance. A wide variety of methods is available for nanoparticle synthesis, affording a broad spectrum of chemical and physical properties. In this work, we report on AgNPs produced by laser ablation synthesis in solution (LASiS), discussing the major features of this approach. Laser ablation synthesis is one of the best candidates, as compared to wet-chemical syntheses, for preparing Ag nano-antimicrobials. In fact, this method allows the preparation of stable Ag colloids in pure solvents without using either capping and stabilizing agents or reductants. LASiS produces AgNPs, which can be more suitable for medical and food-related applications where it is important to use non-toxic chemicals and materials for humans. In addition, laser ablation allows for achieving nanoparticles with different properties according to experimental laser parameters, thus influencing antibacterial mechanisms. However, the concentration obtained by laser-generated AgNP colloids is often low, and it is hard to implement them on an industrial scale. To obtain interesting concentrations for final applications, it is necessary to exploit high-energy lasers, which are quite expensive. In this review, we discuss the pros and cons of the use of laser ablation synthesis for the production of Ag antimicrobial colloids, taking into account applications in the food packaging field. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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11 pages, 1828 KiB  
Review
Silver Camphor Imine Complexes: Novel Antibacterial Compounds from Old Medicines
by Jorge H. Leitão, Silvia A. Sousa, Silvestre A. Leite and Maria Fernanda N. N. Carvalho
Antibiotics 2018, 7(3), 65; https://doi.org/10.3390/antibiotics7030065 - 26 Jul 2018
Cited by 21 | Viewed by 6321
Abstract
The emergence of bacterial resistance to available antimicrobials has prompted the search for novel antibacterial compounds to overcome this public health problem. Metal-based complexes have been much less explored than organic compounds as antimicrobials, leading to investigations of the antimicrobial properties of selected [...] Read more.
The emergence of bacterial resistance to available antimicrobials has prompted the search for novel antibacterial compounds to overcome this public health problem. Metal-based complexes have been much less explored than organic compounds as antimicrobials, leading to investigations of the antimicrobial properties of selected complexes in which silver may occupy the frontline due to its use as medicine since ancient times. Like silver, camphor has also long been used for medicinal purposes. However, in both cases, limited information exists concerning the mechanisms of their antimicrobial action. This work reviews the present knowledge of the antimicrobial properties of camphor-derived silver complexes, focusing on recent research on the synthesis and antimicrobial properties of complexes based on silver and camphor imines. Selected examples of the structure and antimicrobial activity relationships of ligands studied so far are presented, showing the potential of silver camphorimine complexes as novel antimicrobials. Full article
(This article belongs to the Special Issue Silver-Based Antimicrobials)
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