Antimicrobial activity and action of silver

An In Vitro Pilot Study on the Effects of Silver Diamine Fluoride on Periodontal Pathogens and Three-Dimensional Scaffolds of Human Fibroblasts and Epithelial Cells

Objective

The aims of this study were to investigate the antibacterial and cytotoxic effects of silver diamine fluoride (SDF) on periodontal pathogens and human skin constructs, respectively.

Background

SDF has been proven to have bactericidal effects on cariogenic bacteria. No studies to date evaluated the bactericidal effects of SDF on periodontal pathogens nor its effect on epithelium and fibroblasts.

Methods

Streptococcus mutans, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans were cultured in monospecies biofilms, exposed to increasing concentrations of SDF and inoculated on agar plates to assess viability. Human gingival fibroblasts in 2D cultures were exposed to 1 μL of 0.394% of SDF and viewed using real-time imaging. Finally, SDF was applied to human, 3D tissue scaffolds of fibroblasts and keratinocytes, and termed human skin equivalents (HSE). A clinical dose of 38% SDF was applied, and HSE were cultured for 12 hours, 1, 3, 5, and 10 days. The tissue was observed clinically and histologically with hematoxylin and eosin staining and TUNEL.

Results

S. mutans and A. actinomycetemcomitans growth was completely inhibited using all dilutions of SDF, whereas P. gingivalis was still viable with 0.197% and 0.098% of SDF. Single-layer fibroblasts experienced immediate necrosis upon contact with SDF. Application of SDF to HSE showed maturation of a whitish lesion within 24 hours, followed by pigmented, crusted tissue after 3 days. Histological evaluation of treated tissues showed apoptotic cells in the epithelium and upper half of the connective tissue.

Conclusion

Our data suggest that SDF has bactericidal properties against two periodontal pathogens: P. gingivalis and A. actinomycetemcomitans. SDF caused immediate necrosis of monolayer fibroblasts, but does not extend to the full extent of layered fibroblasts in HSE.

Metal Complexes in Diagnosis and Therapy

The use of metal complexes for health and healing has been in use for over the last several millennia and perhaps longer [...].

Durability of Acrylic Cataphoretic Coatings Additivated with Colloidal Silver

In this work, colloidal silver has been added into an acrylic clear cataphoretic bath, evaluating the effect of two different filler amounts on the durability of the composite coatings. The three series of samples were characterized by electron microscopy to assess the possible change in morphology introduced by the silver-based additive. The protective properties of the coatings were evaluated by a salt spray chamber exposure and electrochemical impedance spectroscopy measurements, evidencing the negative effect provided by high amount of silver, which introduced discontinuities in the acrylic matrix. Finally, the durability of composite coatings was studied by exposing them to UV-B radiation, observing a strong phenomenon of silver degradation. Although the coating containing high concentrations of silver demonstrated poor durability, this study revealed that small amounts of silver can be used to provide particular aesthetic features, but also to improve the protective performance of cataphoretic coatings.

Anti-pathogen stainless steel combating COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibits strong stability on conventional stainless steel (SS) surface, with infectious virus detected even after two days, posing a high risk of virus transmission via surface touching in public areas. In order to mitigate the surface toughing transmission, the present study develops the first SS with excellent anti-pathogen properties against SARS-COV-2. The stabilities of SARS-CoV-2, H1N1 influenza A virus (H1N1), and Escherichia coli (E.coli) on the surfaces of Cu-contained SS, pure Cu, Ag-contained SS, and pure Ag were investigated. It is discovered that pure Ag and Ag-contained SS surfaces do not display apparent inhibitory effects on SARS-CoV-2 and H1N1. In comparison, both pure Cu and Cu-contained SS with a high Cu content exhibit significant antiviral properties. Significantly, the developed anti-pathogen SS with 20 wt% Cu can distinctly reduce 99.75% and 99.99% of viable SARS-CoV-2 on its surface within 3 and 6 h, respectively. In addition, the present anti-pathogen SS also exhibits an excellent inactivation ability for H1N1 influenza A virus (H1N1), and Escherichia coli (E.coli). Interestingly, the Cu ion concentration released from the anti-pathogen SS with 10 wt% and 20 wt% Cu was notably higher than the Ag ion concentration released from Ag and the Ag-contained SS. Lift buttons made of the present anti-pathogen SS are produced using mature powder metallurgy technique, demonstrating its potential applications in public areas and fighting the transmission of SARS-CoV-2 and other pathogens via surface touching.

Cellular Effects of Silver Nanoparticle Suspensions on Lung Epithelial Cells and Macrophages

Background: Silver nanoparticles (AgNPs) are used in industrial applications as catalysts, sanitary materials, and health supplements. Generally, AgNPs have shown cytotoxicity such as cell membrane damage. However, the mechanisms of their toxicity have not been completely elucidated. Methods: The cellular effects (cell viability, induction of chemokine and cellular oxidative stress) of two AgNP water suspensions (AgNP-A for cosmetic application and AgNP-B for industrial application) on epithelial-like A549 cells and macrophage-like differentiated THP-1 (dTHP-1) cells were examined. Results: AgNPs caused enhancement of IL-8 expression and oxidative stress. The cellular uptake of AgNP-A cells was observed. However, the cellular uptake of AgNP-B into A549 cells was hardly observed. Moreover, the intracellular Ag level was increased by AgNP suspensions exposure. Cell viability was not affected by AgNP suspensions exposure. Conclusions: AgNPs induce chemokine expression and cellular oxidative stress on culture cells. The intracellular Ag level may be important for these cellular effects.

Nanoplatforms for Promoting Osteogenesis in Ovariectomy-Induced Osteoporosis in the Experimental Model

Background:

Osteoporosis is a debilitating bone ailment characterized by the obvious loss of bone mass and bone microarchitecture impairment.

Objective:

This study aimed to illuminate the in vivo usefulness of nanotechnology as a treatment for osteoporosis via analyzing the effectiveness of nano-hydroxyapatite (nHa), nano-hydroxy- apatite/chitosan (nHa/C), and nano-hydroxyapatite/silver (nHa/S) in mitigation of osteoporosis in ovariectomized rats.

Method:

The characterization of the nHa, nHa/C, and nHa/S was carried out using TEM, SEM, FTIR, and Zeta potential measurements. This in vivo study included 48 adult female rats that were randomized into six groups (8 rats/group): (1) Sham-operated control, (2) osteoporotic, (3) nHa, (4) nHa/C, (5) nHa/S, and (6) Fosamax®. Serum osterix level was quantified using ELISA. Femur bone morphogenetic protein 2 and SMAD1 mRNA levels were evaluated by qPCR. The femur bones were scanned by DEXA for measurement of bone mineral density and bone mineral content. In ad-dition, a histopathological examination of femur bones was performed.

Results:

The present approach denoted that the treatment with nHa, nHa/C, or nHa/S yields a signif-icant rise in serum level of osterix and mRNA levels of bone morphogenetic protein 2 and SMAD1 as well as significant enhancements of bone tissue minerals.

Conclusion:

The findings affirmed the potency of nHa, nHa/C, and nHa/S as auspicious nanoplat-forms for repairing bone defects in the osteoporotic rat model. The positive effect of the inspected nanoformulations arose from bone formation indicators in serum and tissue, and additionally, the reinforcement of bone density and content, which were verified by the histopathological description of bone tissue sections.

Rare-earth ions as antibacterial agents for woven wool fabric

Woven fabrics were bestowed with antibacterial property by the simple adsorption of rare-earth metal ions, and the underlying mechanism was investigated using electron spin resonance (ESR) spectroscopy. The adsorption of Ce³⁺ ions on wool, silk, and cotton fabrics resulted in significant inhibition of Staphylococcus aureus (a gram-positive bacterium), with maximum antibacterial activities (viable bacterial count compared to the reference) of 4.7, 5.8, and 5.2, respectively. Even after 50 wash cycles, the values remained at 3.9, 2.9, and 4.8, respectively. The adsorption of La³⁺ and Gd³⁺ ions on wool fabrics also resulted in antibacterial activities of 5.8 and 5.9, respectively. In addition, wool adsorbed with Ce³⁺ exhibits a satisfactory antibacterial activity of 6.2 against Escherichia coli (a gram-negative bacterium). Such bacterial inhibition is attributed to Fenton reactions between the adsorbed rare-earth ions and hydrogen peroxide (H₂O₂) produced during bacterial metabolism, as determined from the ESR spectra collected using the spin trap method in the presence of H₂O₂. The safety of cerium nitrate was also investigated, and no significant issues arose, indicating that it was a safe antibacterial agent. This facile method of imparting antibacterial properties to natural fabrics may be useful for preventing infections in humans.

Facile Route to Effective Antimicrobial Aluminum Oxide Layer Realized by Co-Deposition with Silver Nitrate

The emergence and spreading of the SARS-CoV-2 pandemic has forced the focus of attention on a significant issue: the realization of antimicrobial surfaces for public spaces, which do not require extensive use of disinfectants. Silver represents one of the most used elements in this context, thanks to its excellent biocidal performance. This work describes a simple method for the realization of anodized aluminum layers, whose antimicrobial features are ensured by the co-deposition with silver nitrate. The durability and the chemical resistance of the samples were evaluated by means of several accelerated degradation tests, such as the exposure in a salt spray chamber, the contact with synthetic sweat and the scrub test, highlighting the residual influence of silver in altering the protective behavior of the alumina layers. Furthermore, the ISO 22196:2011 standard was used as the reference protocol to set up an assay to measure the effective antibacterial activity of the alumina-Ag layers against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, even at low concentrations of silver. Finally, the Ag-containing aluminum oxide layers exhibited excellent antimicrobial performances also following the chemical–physical degradation processes, ensuring good durability over time of the antimicrobial surfaces. Overall, this work introduces a simple route for the realization of anodized aluminum surfaces with excellent antibacterial properties.

Development of a low-temperature extrusion process for production of GRAS bioactive-polymer loaded compounds for targeting antimicrobial-resistant (AMR) bacteria

Antimicrobial resistance (AMR) is recognised globally as one of the greatest threats to human and animal health; thus, discovery of alternative antibacterial agents to address AMR is a priority challenge. This study constitutes the first report of a low-melting temperature, polymer- extrusion process for the smart delivery of thermally-sensitive antimicrobial bioactives, including generally-regarded-as-safe (GRAS) bioactives derived from various sources. Bioactives were assessed before and after extrusion by determining their respective minimum inhibitory concentrations (MIC). WHO-priority AMR-bacterial isolates causing zoonotic infections were evaluated along with use of standard ATCC strains. Findings revealed that this copolymer method was capable of delivering thermally-sensitive bioactives with varying degrees of growth inhibition against the AMR-bacterial strains. The extrusion process was found to increase the effect of nisin against MRSA (4-fold increase) and L. monocytogenes (6.4-fold increase), silver nitrate (AgNO₃) against E. coli (3.6-fold increase) and S. epidermidis (1.25-fold increase), and chitosan against S. aureus (1.25-fold). Findings show the potential applicability of this polymer extrusion process for developing future bioactive-loaded polymer compounds; thus, highlighting the potential of converging bio-based industry with novel materials for enabling 'One-Health' solutions.

Experimental evolution of Pseudomonas putida under silver ion versus nanoparticle stress

Whether the antibacterial properties of silver nanoparticles (AgNPs) are simply due to the release of silver ions (Ag⁺ ) or, additionally, nanoparticle-specific effects, is not clear. We used experimental evolution of the model environmental bacterium Pseudomonas putida to ask whether bacteria respond differently to Ag⁺ or AgNP treatment. We pre-evolved five cultures of strain KT2440 for 70 days without Ag to reduce confounding adaptations before dividing the fittest pre-evolved culture into five cultures each, evolving in the presence of low concentrations of Ag⁺ , well-defined AgNPs or Ag-free controls for a further 75 days. The mutations in the Ag⁺ or AgNP evolved populations displayed different patterns that were statistically significant. The non-synonymous mutations in AgNP-treated populations were mostly associated with cell surface proteins, including cytoskeletal membrane protein (FtsZ), membrane sensor and regulator (EnvZ and GacS) and periplasmic protein (PP_2758). In contrast, Ag⁺ treatment was selected for mutations linked to cytoplasmic proteins, including metal ion transporter (TauB) and those with metal-binding domains (ThiL and PP_2397). These results suggest the existence of AgNP-specific effects, either caused by sustained delivery of Ag⁺ from AgNP dissolution, more proximate delivery from cell-surface bound AgNPs, or by direct AgNP action on the cell's outer membrane.

"Green" Biomaterials: The Promising Role of Honey

The development of nanotechnology has allowed us to better exploit the potential of many natural compounds. However, the classic nanotechnology approach often uses both dangerous and environmentally harmful chemical compounds and drastic conditions for synthesis. Nevertheless, “green chemistry” techniques are revolutionizing the possibility of making technology, also for tissue engineering, environmentally friendly and cost-effective. Among the many approaches proposed and among several natural compounds proposed, honey seems to be a very promising way to realize this new “green” approach.

Antimicrobial silver dressings: a review of emerging issues for modern wound care

Skin is an important barrier to pathogenic microorganisms and plays a critical role in a ctivation of innate immune responses. When the skin barrier is breached following wounding or burn injury, pathogens can invade and complicate healing with infection resulting in delayed healing and symptomatic scarring. Wound infection is a significant problem after burn injury and in patients with chronic wounds. Antimicrobial silver has had a significant role in wound antisepsis throughout history and, given the rise in community acquired antibiotic resistance, silver dressings are now commonly used to combat wound infection. The multi-modal mechanism of action, low potential for toxicity and formation of microbial resistance makes silver dressings suitable tools against a wide array of clinically important microbes. There are, however, a number of issues with silver dressings including a conflicting evidence base, the important environmental consideration of nanoparticle manufacture, and the significant cost of these products. One solution may be to adopt an 'opened-but-unused' means of wound care whereby bulk dressing materials are used piecemeal and stored in between dressing changes to increase the cost-effectiveness and reduced wastage. There is, however, little literature on this topic and so in vitro and clinical research must be performed to consider the efficacy of active ingredient dressings in wound care including silver dressings once opened and stored.

Synthesis, characterization, antimicrobial and antibiofilm activity, and molecular docking analysis of NHC precursors and their Ag-NHC complexes

Microorganisms attach to surfaces and interfaces and form biofilms which create a sheltered area for host cell response. Therefore, biofilms provide troubles in fields such as medicine, food, and pharmaceuticals. Inhibition of formation of biofilms through hindering of quorum sensing could be a method for the production of new generation antibiotics. In this study, four new benzimidazole type NHC precursors (1-allyl-3-benzyl-5,6-dimethylbenzimidazolium chloride, 1-allyl-3-(2,4,6-trimethylbenzyl)-5,6-dimethylbenzimidazolium chloride, 1-allyl-3-(2,3,5,6-tetramethylbenzyl)-5,6-dimethylbenzimidazolium chloride, and 1-allyl-3-(2,3,4,5,6-pentamethylbenzyl)-5,6-dimethylbenzimidazolium chloride and Ag-NHC complexes of these molecules were synthesized and characterized by elemental analysis, FT-IR spectroscopy, 1H, and 13C{1H} NMR spectroscopy, LC-MS, and single crystal crystallography. Antimicrobial and biofilm formation inhibition activities of the molecules were evaluated. In addition, the activities of the molecules were examined in detail by molecular docking analysis. According to the results obtained, higher activity was achieved with the complex molecules when compared with the benzimidazole derivative ligands.

Advances in Nanotechnology towards Development of Silver Nanoparticle-Based Wound-Healing Agents

Since antiquity, silver-based therapies have been used in wound healing, wound care and management of infections to provide adequate healing. These therapies are associated with certain limitations, such as toxicity, skin discolouration and bacterial resistance, which have limited their use. As a result, new and innovative wound therapies, or strategies to improve the existing therapies, are sought after. Silver nanoparticles (AgNPs) have shown the potential to circumvent the limitations associated with conventional silver-based therapies as described above. AgNPs are effective against a broad spectrum of microorganisms and are less toxic, effective at lower concentrations and produce no skin discolouration. Furthermore, AgNPs can be decorated or coupled with other healing-promoting materials to provide optimum healing. This review details the history and impact of silver-based therapies leading up to AgNPs and AgNP-based nanoformulations in wound healing. It also highlights the properties of AgNPs that aid in wound healing and that make them superior to conventional silver-based wound treatment therapies.

Strategies toward development of antimicrobial biomaterials for dental healthcare applications

Several approaches for elimination of oral pathogens are being explored at the present time since oral diseases remain prevalent affecting approximately 3.5 billion people worldwide. Need for antimicrobial biomaterials in dental healthcare include but is not restricted to designing resin composites and adhesives for prevention of dental caries. Constant efforts are also being made to develop antimicrobial strategies for clearance of endodontic space prior root canal treatment and for treatment of periimplantitis and periodontitis. This article discusses various conventional and nanotechnology-based strategies to achieve antimicrobial efficacy in dental biomaterials. Recent developments in the design and synthesis of antimicrobial peptides and antifouling zwitterionic polymers to effectively lessen the risks of antimicrobial drug resistance are also outlined in this review. Further, the role of contemporary strategies such as use of smart biomaterials, ionic solvent-based biomaterials and quorum quenchers incorporated biomaterials in the elimination of dental pathogens are described in detail. Lastly, we mentioned the approach of using polymers to print custom-made three-dimensional antibacterial dental products via additive manufacturing technologies. This review provides a critical perspective on the chemical, biomimetic, and engineering strategies intended for developing antimicrobial biomaterials that have the potential to substantially improve the dental health.

Antiviral nanoparticles for sanitizing surfaces: A roadmap to self-sterilizing against COVID-19

Nanoparticles provide new opportunities in merging therapeutics and new materials, with current research efforts just beginning to scratch the surface of their diverse benefits and potential applications. One such application, the use of inorganic nanoparticles in antiseptic coatings to prevent pathogen transmission and infection, has seen promising developments. Notably, the high reactive surface area to volume ratio and unique chemical properties of metal-based nanoparticles enables their potent inactivation of viruses. Nanoparticles exert their virucidal action through mechanisms including inhibition of virus-cell receptor binding, reactive oxygen species oxidation and destructive displacement bonding with key viral structures. The prevention of viral outbreaks is one of the foremost challenges to medical science today, emphasizing the importance of research efforts to develop nanoparticles for preventative antiviral applications. In this review, the use of nanoparticles to inactivate other viruses, such as influenza, HIV-1, or norovirus, among others, will be discussed to extrapolate broad-spectrum antiviral mechanisms that could also inhibit SARS-CoV-2 pathogenesis. This review analyzes the published literature to highlight the current state of knowledge regarding the efficacy of metal-based nanoparticles and other antiviral materials for biomedical, sterile polymer, and surface coating applications.

A New Approach for the Green Biosynthesis of Silver Oxide Nanoparticles Ag2O, Characterization and Catalytic Application

In this paper, a facile and green approach for the synthesis of silver oxide nanoparticles Ag2O NPs was performed using the extract of the wild plant Herniaria hirsuta (H. hirsuta). Different spectral methods were used for the characterization of the biosynthesized Ag2O NPs, ultraviolet-visible (UV-Vis) spectroscopy gave a surface plasmon resonance (SPR) peak of Ag2O NPs is 430 nm, estimation of direct and indirect forbidden gap bands are respectively 3.76 eV and 3.68 eV; Fourier transform infrared (FTIR) spectral analysis revealed the groups responsible for the stability and synthesis of Ag2O NPs. The morphology of Ag2O NPs was studied by scanning electron microscopy (SEM) showing a nearly spherical shape of Ag2O NPs, and X-ray diffraction (XRD) study confirmed the crystallinity of Ag2O NPs with a crystallinity size of 15.51 nm. The catalytic activity of Ag2O NPs, as well as the rings number were studied by the degradation of methylene blue dye. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Nanocomposite Biopolymer Arboblend V2 Nature AgNPs

Due to the pressing problems of today’s world, regarding both the finding of new, environmentally friendly materials which have the potential to replace classic ones, and the need to limit the accelerated spread of bacteria in hospitals, offices and other types of spaces, many researchers have chosen to develop their work in this field. Thus, biopolymeric materials have evolved so much that they are gradually becoming able to remove fossil-based plastics from major industries, which are harmful to the environment and implicitly to human health. The biopolymer employed in the present study, Arboblend V2 Nature with silver nanoparticle content (AgNP) meets both aspects mentioned above. The main purpose of the paper is to replace several parts and products in operation which exhibit antibacterial action, preventing the colonization and proliferation of bacteria (Streptococcus pyogenes and Staphylococcus aureus, by using the submerged cultivation method), but also the possibility of degradation in different environments. The biopolymer characterization followed the thermal behavior of the samples, their structure and morphology through specific analyses, such as TGA (thermogravimetric analysis), DSC (differential scanning calorimetry), SEM (scanning electron microscopy) and XRD (X-ray diffraction). The obtained results offer the possibility of use of said biocomposite material in the medical field because of its antibacterial characteristics that have proved to be positive, and, therefore, suitable for such applications. The thermal degradation and the structure of the material highlighted the possibility of employing it in good conditions at temperatures up to 200 °C. Two types of samples were used for thermal analysis: first, in the form of granules coated with silver nanoparticles, and second, test specimen cut from the sample obtained by injection molding from the coated granules with silver nanoparticles.

Oxidative Inactivation of SARS-CoV-2 on Photoactive AgNPs@TiO2 Ceramic Tiles

The current SARS-CoV-2 pandemic causes serious public health, social, and economic issues all over the globe. Surface transmission has been claimed as a possible SARS-CoV-2 infection route, especially in heavy contaminated environmental surfaces, including hospitals and crowded public places. Herein, we studied the deactivation of SARS-CoV-2 on photoactive AgNPs@TiO₂ coated on industrial ceramic tiles under dark, UVA, and LED light irradiations. SARS-CoV-2 inactivation is effective under any light/dark conditions. The presence of AgNPs has an important key to limit the survival of SARS-CoV-2 in the dark; moreover, there is a synergistic action when TiO₂ is decorated with Ag to enhance the virus photocatalytic inactivation even under LED. The radical oxidation was confirmed as the the central mechanism behind SARS-CoV-2 damage/inactivation by ESR analysis under LED light. Therefore, photoactive AgNPs@TiO₂ ceramic tiles could be exploited to fight surface infections, especially during viral severe pandemics.

Silver-N-heterocyclic carbene complexes-catalyzed multicomponent reactions: Synthesis, spectroscopic characterization, density functional theory calculations, and antibacterial study

Nowadays, silver-N-heterocyclic carbene (silver-NHCs) complexes are widely used in medicinal chemistry due to their low toxic nature toward humans. Due to the success of silver-NHCs in medicinal applications, interest in these compounds is rapidly increasing. Therefore, the interaction of N,N-disubstituted benzimidazolium salts with Ag₂ O in dichloromethane to prepare novel Ag(I)-NHCs complexes was carried out at room temperature for 120 h in the absence of light. The obtained complexes were identified and characterized by ¹ H and ¹³ C nuclear magnetic resonance, Fourier-transform infrared, UV-Vis, and elemental analysis techniques. Then, the silver complexes were applied for three-component coupling reactions of aldehydes, amines, and alkynes. The effect of changing the alkyl substituent on the NHCs ligand on the catalytic performance was investigated. In addition, it has been found that the complexes are antimicrobially active and show higher activity than the free ligand. The silver-carbene complexes showed antimicrobial activity against specified microorganisms with MIC values between 0.24 and 62.5 μg/ml. These results showed that the silver-NHC complexes exhibit an effective antimicrobial activity against bacterial and fungal strains. A density functional theory calculation study was performed to identify the stability of the obtained complexes. All geometries were optimized employing an effective core potential basis, such as LANL2DZ for the Ag atom and 6-311+G(d,p) for all the other atoms in the gas phase. Electrostatic potential surfaces and LUMO-HOMO energy were computed. Transition energies and excited-state structures were obtained from the time-dependent density functional theory calculations.

Silver-Releasing Micro-/Nanoporous Coating on Additively Manufactured Macroporous Ti-Ta-Nb-Zr Scaffolds with High Osseointegration and Antibacterial Properties

The two major problems of titanium alloy surface of bone/dental implants were the lack of native tissue integration and associated infection. To solve these problems, the development of self-defending implants with intrinsic osteogenic properties has been highlighted, in which titanium alloy surfaces of bone/dental implants are endowed with antibacterial property by silver (Ag) incorporated in biomaterials. In this study, we biofunctionalized the surface of selective laser melting (SLM) manufactured volume-porous Ti-Ta-Nb-Zr scaffolds by using plasma electrolytic oxidation (PEO) as a way to eliminate the peri-operative bacterial load and promote osseointegration. In the experiment, the PEO process operated with three different concentration (1, 1, and 2 g/L) of a AgNO3 solution. As a result, a titanium oxide coating embedded with calcium and phosphorous and Ag was formed by one-step PEO treatment, and a presence of HAp was detected by X-ray diffraction (XRD) and XPS. In addition, Ag ions were found to be released from the scaffolds for at least 28 days, resulting in an effective prevention of bacterial adhesion and a decrease of the number of planktonic bacteria, with no sign of cytotoxicity shown simultaneously. Highly porosity micropores were formed on the surface of scaffolds after oxidation, and the mechanical properties did not show any signs of change. Besides, a strong calcium deposition and osteoconductive effect were found on the surface of PEO-treated Ag scaffolds. To sum up, this study reveals the potential of PEO coatings to biofunctionalize SLM Ti-Ta-Nb-Zr scaffolds with antibacterial agents. The biomaterials developed here, therefore, exploit the biofunctionalized behavior of Ag to offer strong antibacterial behavior and osteogenic promotion without cytotoxicity of Ag against mammalian cells.

The effect of the combined use of silver diamine fluoride and potassium iodide in disrupting the plaque biofilm microbiome and alleviating tooth discoloration: A systematic review

Silver diamine fluoride (SDF) is used in minimally invasive dentistry for arresting dental caries. However, discoloration of teeth is a significant side effect that has limited the use of SDF. Hence, the application of potassium iodide (KI) following SDF has been proposed to ameliorate the staining. Although antimicrobial activity is one of the major mechanisms of the caries-arresting effect of SDF, the antimicrobial potency of SDF/KI combination is unclear. Thus, the primary objective of this systematic review was to appraise the studies on the antimicrobial efficacy of SDF/KI combination on cariogenic microbes. The secondary objective was to summarize the evidence on the potential of KI in reducing the discoloration associated with the application of SDF. Electronic databases of Medline via PubMed, Cochrane Library, Web of Science, and EBSCO host were searched for English language manuscripts from January 2005 to 15th November 2020. The reference lists of these manuscripts were manually searched for additional studies. Twelve studies were included in the final analysis, seven of which have investigated the antimicrobial efficacy of SDF/KI, and the rest have examined the anti-staining potential of KI. The exploratory findings from the reviewed articles revealed the promising antimicrobial potential of SDF/KI on cariogenic microbes associated with dentine caries. There is, however, contradictory evidence on the effect of SDF/KI on tooth color. The reviewed in-vitro studies indicated significant effectiveness of KI in preventing staining. A clinical trial on primary dentition showed 25% reduction in the incidence of staining by SDF after applying KI, while a clinical study on root caries in adults showed no significant effect. Within the methodological limitations of this review, we conclude that for arresting dental caries, SDF could be combined with KI, as there may be a lower likelihood of staining. Further, well-designed clinical trials on the antimicrobial and anti-staining effect of SDF/KI are needed to obtain more robust evidence.

A review on nanostructured silver as a basic ingredient in medicine: physicochemical parameters and characterization

Recent studies with silver nanoparticles (AgNPs) and the history of silver metal as a broad-spectrum bactericidal and virucidal agent, places silver as one of the future biocidal candidates in the field of nanomedicine to eliminate bacteria and viruses, especially multidrug resistant ones. In this review, we have described the various morphologies of AgNPs and correlated the enhanced bactericidal activity with their prominent {111} facets. In addition to prioritizing the characterization we have also discussed the importance of quantifying AgNPs and silver ion content (Ag+) and their different mechanisms at the chemical, biological, pharmacological, and toxicological levels. The mechanism of action of AgNPs against various bacteria and viruses including the SARS-CoV-2 was analyzed in order to understand its effectiveness as an antimicrobial agent with therapeutic efficacy and low toxicity. Further, there is the need to characterize AgNPs and quantify the content of free Ag+ for the implementation of new systematic studies of this promising agent in nanomedicine and in clinical practice.

Silver(I)-N-heterocyclic carbene complexes challenge cancer; evaluation of their anticancer properties and in silico studies

Because of the continuous need for efficient therapeutic agents against various kinds of cancers and infectious diseases, the pharmaceutical industry has to find new candidates and strategies to develop novel and efficient drugs. They increasingly use computational tools in R&D stages for screening extensive sets of drug candidates before starting pre-clinical and clinical trials. N-Heterocyclic carbenes (NHCs) can be evaluated as good drug candidates because they offer both anti-cancer and anti-inflammatory features with their general low-toxicity profiles. To date, different kinds of NHCs (Cu, Co, Ni, Au, Ag, Ru, etc.) have been synthesized and their therapeutic uses has been shown. Here, we have reviewed the recent studies focused on Ag(I)-NHC complexes and their anti-cancer activities. Also, existing examples of the usage of density functional theory and structure-activity relationship have been evaluated.

Evaluation of metal-based antimicrobial compounds for the treatment of bacterial pathogens

Antimicrobial resistance (AMR) is one of the greatest global health challenges of modern times and its prevalence is rising worldwide. AMR within bacteria reduces the efficacy of antibiotics and increases both the morbidity and the mortality associated with bacterial infections. Despite this growing risk, few antibiotics with a novel mode of action are being produced, leading to a lack of antibiotics that can effectively treat bacterial infections with AMR. Metals have a history of antibacterial use but upon the discovery of antibiotics, often became overlooked as antibacterial agents. Meanwhile, metal-based complexes have been used as treatments for other diseases, such as the gold-containing drug auranofin, used to treat rheumatoid arthritis. Metal-based antibacterial compounds have novel modes of action that provide an advantage for the treatment of bacterial infections with resistance to conventional antibiotics. In this review, the antibacterial activity, mode of action, and potential for systemic use of a number of metal-based antibacterial complexes are discussed. The current limitations of these compounds are highlighted to determine if metal-based agents are a potential solution for the treatment of bacterial infections, especially those resistant to conventional antibiotics.

Investigating the Possibility of Green Synthesis of Silver Nanoparticles Using Vaccinium arctostaphlyos Extract and Evaluating Its Antibacterial Properties

Objective

Vaccinium genus plants have medicinal value, of which Vaccinium arctostaphylos (Caucasian whortleberry or Qare-Qat in the local language) is the only available species in Iran. Public tendency to use herbal remedies and natural products such as synthesized nanoparticles is increasing due to the proof of the destructive side effects of chemical drugs. Nanosilver products have been effective against more than 650 microbe types. This study was aimed at assessing the possibility of green synthesis of silver nanoparticles using Vaccinium arctostaphylos aqueous extract and at evaluating its antibacterial properties, as well.

Materials and Methods

In order to synthesize silver nanoparticles, different volumes of Vaccinium arctostaphylos aqueous extract (3, 5, 10, 15, and 30 ml) were assessed with different silver nitrate solution concentrations (0.5, 1, 3, 5, and 10 mM) and different reaction time durations (1, 3, 5, 10, and 20 minutes) at room temperature using a rotary shaker with a speed of 150 rpm. Ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were carried out. The antibacterial activity of the aqueous extract and the synthesized nanoparticles was evaluated, as well.

Results

Silver nanoparticle formation process was confirmed with XRD analysis, transmission electron microscopy (TEM), and FTIR spectroscopy. The UV-Vis spectroscopy of silver colloidal nanoparticles showed a surface plasmon resonance peak at 443 nm under optimal conditions (3 ml aqueous extract volume, 1 mM silver nitrate solution concentration, and 3 min reaction time under sunlight exposure). The reduction of silver ions to silver nanoparticles in solution was confirmed, as well. Based on X-ray diffraction analysis, the size of silver nanoparticles was in the range of 7-16 nm. TEM images showed an even distribution of silver nanoparticles, with a spherical shape. FTIR spectroscopy demonstrated the presence of different functional groups of oxygenated compounds such as carboxyl, hydroxyl, and nitrogenous groups. The antibacterial properties of the synthesized nanoparticles were confirmed.

Conclusion

The synthesized nanoparticles showed more antibacterial properties against gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) than gram-negative ones (Escherichia coli and Salmonella enteritidis).

Mechanochemistry as an Alternative Method of Green Synthesis of Silver Nanoparticles with Antibacterial Activity: A Comparative Study

This study shows mechanochemical synthesis as an alternative method to the traditional green synthesis of silver nanoparticles in a comparative manner by comparing the products obtained using both methodologies and different characterization methods. As a silver precursor, the most commonly used silver nitrate was applied and the easily accessible lavender (Lavandula angustofolia L.) plant was used as a reducing agent. Both syntheses were performed using 7 different lavender:AgNO3 mass ratios. The synthesis time was limited to 8 and 15 min in the case of green and mechanochemical synthesis, respectively, although a significant amount of unreacted silver nitrate was detected in both crude reaction mixtures at low lavender:AgNO3 ratios. This finding is of particular interest mainly for green synthesis, as the potential presence of silver nitrate in the produced nanosuspension is often overlooked. Unreacted AgNO3 has been removed from the mechanochemically synthesized samples by washing. The nanocrystalline character of the products has been confirmed by both X-ray diffraction (Rietveld refinement) and transmission electron microscopy. The latter has shown bimodal size distribution with larger particles in tens of nanometers and the smaller ones below 10 nm in size. In the case of green synthesis, the used lavender:AgNO3 ratio was found to have a decisive role on the crystallite size. Silver chloride has been detected as a side-product, mainly at high lavender:AgNO3 ratios. Both products have shown a strong antibacterial activity, being higher in the case of green synthesis, but this can be ascribed to the presence of unreacted AgNO3. Thus, one-step mechanochemical synthesis (without the need to prepare extract and performing the synthesis as separate steps) can be applied as a sustainable alternative to the traditional green synthesis of Ag nanoparticles using plants.

The antimicrobial activity of silver acetate against Acinetobacter baumannii in a Galleria mellonella infection model

Background

The increasing prevalence of bacterial infections that are resistant to antibiotic treatment has caused the scientific and medical communities to look for alternate remedies aimed at prevention and treatment. In addition to researching novel antimicrobials, there has also been much interest in revisiting some of the earliest therapies used by man. One such antimicrobial is silver; its use stretches back to the ancient Greeks but interest in its medicinal properties has increased in recent years due to the rise in antibiotic resistance. Currently antimicrobial silver is found in everything from lunch boxes to medical device implants. Though much is claimed about the antimicrobial efficacy of silver salts the research in this area is mixed.

Methods

Herein we investigated the efficacy of silver acetate against a carbapenem resistant strain of Acinetobacter baumannii to determine the in vitro activity of this silver salt against a World Health Organisation designated category I critical pathogen. Furthermore, we use the Galleria mellonella larvae model to assess toxicity of the compound and its efficacy in treating infections in a live host.

Results

We found that silver acetate can be delivered safely to Galleria at medically relevant and antimicrobial levels without detriment to the larvae and that administration of silver acetate to an infection model significantly improved survival. This demonstrates the selective toxicity of silver acetate for bacterial pathogens but also highlights the need for administration of well-defined doses of the antimicrobial to provide an efficacious treatment.

Pharmacokinetics of Bio-shell-silver-core Nanoparticles (AgNP) in Sprague-Dawley Rats - In Vivo Study

BACKGROUND

Silver nanoparticles have been widely used in the field of nanomedicine. A comprehensive understanding of their pharmacokinetics is crucial for proper risk assessment and safe biomedical applications.

OBJECTIVES

The purpose of this study was to investigate the safety of silver nanoparticles by determining their potential toxicity following 28 days of administration in Sprague-Dawley rats.

METHODS

The silver nanoparticles were administered by intravenous injection at the doses of 100, 200 and 500 μg/kg body weight for 28 consecutive days. Animals in the control group were received sterile water for injection. Each group consists of 10 male and 10 female rats.

RESULTS

No treatment-related effects were seen in any of the parameters monitored in rats given 100, 200 and 500 μg/kg body weight/day of silver nanoparticles.

CONCLUSION

The study proved that the use of up to 500 μg/kg body weight biosynthesized silver nanoparticles have no toxic effect on the target organs and found safe. However, the safety of the nanoparticles might be attributed to the covering of biological moieties on nanoparticles. Hence, the biofunctionalized nanoparticles can be safely used by selecting the required size and dose in medicines and drug delivery systems.

Effects of silver diamine fluoride preparations on biofilm formation of Streptococcus mutans

Effects of silver diamine fluoride preparations (SDFs) on cariogenic biofilm formation on root dentin (RD) were investigated. Streptococcus mutans (S. mutans) biofilms were formed on bovine RD blocks coated with one of three the SDFs (38%-SDF, 3.8%-SDF and 35%-SDF+potassium-iodide; SDF+KI) and a non-coated Control which were quantified (spectrometric-measurement) and thickness measured (optical coherence tomography) after 20 h. Bacterial viability test (BacLight) and biofilm-morphometry (SEM) of 2 h biofilms were also performed. The amounts of biofilms (bacteria and water insoluble glucan) and the thickness of biofilm were minimum on 38%-SDF specimen; 3.8%-SDF and SDF+KI had significantly more than that, but had significantly less than Control (p<0.05). Most S. mutans cells found dead and morphology damaged by 38%-SDF. Some dead bacteria and remarkably damaged biofilms were observed in case of 3.8%-SDF and SDF+KI. Inhibition potential of 3.8%-SDF and SDF+KI on S. mutans biofilm formation is almost similar, although not equivalent to 38%-SDF.

Silver (I) N-Heterocyclic Carbene Complexes: A Winning and Broad Spectrum of Antimicrobial Properties

The evolution of antibacterial resistance has arisen as the main downside in fighting bacterial infections pushing researchers to develop novel, more potent and multimodal alternative drugs.Silver and its complexes have long been used as antimicrobial agents in medicine due to the lack of silver resistance and the effectiveness at low concentration as well as to their low toxicities compared to the most commonly used antibiotics. N-Heterocyclic Carbenes (NHCs) have been extensively employed to coordinate transition metals mainly for catalytic chemistry. However, more recently, NHC ligands have been applied as carrier molecules for metals in anticancer applications. In the present study we selected from literature two NHC-carbene based on acridinescaffoldand detailed nonclassicalpyrazole derived mono NHC-Ag neutral and bis NHC-Ag cationic complexes. Their inhibitor effect on bacterial strains Gram-negative and positivewas evaluated. Imidazolium NHC silver complex containing the acridine chromophore showed effectiveness at extremely low MIC values. Although pyrazole NHC silver complexes are less active than the acridine NHC-silver, they represent the first example of this class of compounds with antimicrobial properties. Moreover all complexesare not toxic and they show not significant activity againstmammalian cells (Hek lines) after 4 and 24 h. Based on our experimental evidence, we are confident that this promising class of complexes could represent a valuable starting point for developing candidates for the treatment of bacterial infections, delivering great effectiveness and avoiding the development of resistance mechanisms.

Controlled Growth of Silver Oxide Nanoparticles on the Surface of Citrate Anion Intercalated Layered Double Hydroxide

Silver oxide nanoparticles with controlled particle size were successfully obtained utilizing citrate-intercalated layered double hydroxide (LDH) as a substrate and Ag+ as a precursor. The lattice of LDH was partially dissolved during the reaction by Ag+. The released hydroxyl and citrate acted as a reactant in crystal growth and a size controlling capping agent, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, and microscopic measurements clearly showed the development of nano-sized silver oxide particles on the LDH surface. The particle size, homogeneity and purity of silver oxide were influenced by the stoichiometric ratio of Ag/Al. At the lowest silver ratio, the particle size was the smallest, while the chemical purity was the highest. X-ray photoelectron spectroscopy and UV-vis spectroscopy results suggested that the high Ag/Al ratio tended to produce silver oxide with a complex silver environment. The small particle size and homogeneous distribution of silver oxide showed advantages in antibacterial efficacy compared with bulk silver oxide. LDH with an appropriate ratio could be utilized as a substrate to grow silver oxide nanoparticles with controlled size with effective antibacterial performance.

Effects of electrical biostimulation and silver ions on porcine fibroblast cells

The medical applications of electrical biostimulation and silver ions have been evaluated in laboratory experiments and clinical studies for more than two decades. Their effects on preventing infection and promoting wound healing have been described. However, little is known about the role of electrical biostimulation and/or silver ion on changes in cellular transcriptome dynamics. To our knowledge, few studies have been conducted to investigate the potential of electrical biostimulation and silver ions in cell reprogramming. Besides, it is essential to assess any possible adverse effects or potential benefits of the silver ions on mammalian cells to address its safety concerns and to improve silver medical products. In this study, we investigated transcriptomic changes in porcine fibroblast cells in response to electrical biostimulation in the presence of silver ions. Exposed cells presented distinct morphological changes after treatment, which was mainly due to the exposure of silver ions rather than the electrical current itself. Gene expression analyses suggested that electrical biostimulation and silver ions did not increase the expression of pluripotency genes. Interestingly, a set of genes related to cellular metabolic processes were differentially expressed after cells were exposed to electrically generated silver ions for 21 hours. We found that 2.00 mg/L of electrically generated silver ion caused an increase of ATP generation and an increase of the total pool of NAD⁺ and NADH, while ROS production did not change. Aside from toxic effects, the results reported herein demonstrate the alternative effects of silver ions on mammalian cells, especially an oxidative phosphorylation burst. To our knowledge, this response of mammalian cells to silver ions has not been described previously. Although the function of this burst is not understood, it may lead to alterations in cellular activities such as metabolic remodeling and cell reprogramming, and/or serve an as-yet unknown function in neutralization or detoxification of the silver ions within the cells.

Synthesis, Spectroscopy, Single-Crystal Structure Analysis and Antibacterial Activity of Two Novel Complexes of Silver(I) with Miconazole Drug

In a previous article, we reported on the higher toxicity of silver(I) complexes of miconazole [Ag(MCZ)₂NO₃ (1)] and [Ag(MCZ)₂ClO₄ (2)] in HepG2 tumor cells compared to the corresponding salts of silver, miconazole and cisplatin. Here, we present the synthesis of two silver(I) complexes of miconazole containing two new counter ions in the form of Ag(MCZ)₂X (MCZ = 1-[2-(2,4-dichlorobenzyloxy)-2-(2,4-dichlorophenyl)ethyl]-1H-imidazole]; X = BF₄⁻ (3), SbF₆⁻ (4)). The novel silver(I) complexes were characterized by elemental analysis, ¹H NMR, ¹³C NMR and infrared (IR) spectroscopy, electrospray ionization (ESI)-MS spectrometry and X-ray-crystallography. In the present study, the antimicrobial activity of all obtained silver(I) complexes of miconazole against six strains of Gram-positive bacteria, five strains of Gram-negative bacteria and yeasts was evaluated. The results were compared with those of a silver sulfadiazine drug, the corresponding silver salts and the free ligand. Silver(I) complexes exhibited significant activity against Gram-positive bacteria, which was much better than that of silver sulfadiazine and silver salts. The highest antimicrobial activity was observed for the complex containing the nitrate counter ion. All Ag(I) complexes of miconazole resulted in much better inhibition of yeast growth than silver sulfadiazine, silver salts and miconazole. Moreover, the synthesized silver(I) complexes showed good or moderate activity against Gram-negative bacteria compared to the free ligand.

Key Properties of a Bioactive Ag-SiO2/TiO2 Coating on NiTi Shape Memory Alloy as Necessary at the Development of a New Class of Biomedical Materials

Recent years have seen the dynamic development of methods for functionalizing the surface of implants using biomaterials that can mimic the physical and mechanical nature of native tissue, prevent the formation of bacterial biofilm, promote osteoconduction, and have the ability to sustain cell proliferation. One of the concepts for achieving this goal, which is presented in this work, is to functionalize the surface of NiTi shape memory alloy by an atypical glass-like nanocomposite that consists of SiO2-TiO2 with silver nanoparticles. However, determining the potential medical uses of bio(nano)coating prepared in this way requires an analysis of its surface roughness, tribology, or wettability, especially in the context of the commonly used reference coat-forming hydroxyapatite (HAp). According to our results, the surface roughness ranged between (112 ± 3) nm (Ag-SiO2)-(141 ± 5) nm (HAp), the water contact angle was in the range (74.8 ± 1.6)° (Ag-SiO2)-(70.6 ± 1.2)° (HAp), while the surface free energy was in the range of 45.4 mJ/m2 (Ag-SiO2)-46.8 mJ/m2 (HAp). The adhesive force and friction coefficient were determined to be 1.04 (Ag-SiO2)-1.14 (HAp) and 0.247 ± 0.012 (Ag-SiO2) and 0.397 ± 0.034 (HAp), respectively. The chemical data showed that the release of the metal, mainly Ni from the covered NiTi substrate or Ag from Ag-SiO2 coating had a negligible effect. It was revealed that the NiTi alloy that was coated with Ag-SiO2 did not favor the formation of E. coli or S. aureus biofilm compared to the HAp-coated alloy. Moreover, both approaches to surface functionalization indicated good viability of the normal human dermal fibroblast and osteoblast cells and confirmed the high osteoconductive features of the biomaterial. The similarities of both types of coat-forming materials indicate an excellent potential of the silver-silica composite as a new material for the functionalization of the surface of a biomaterial and the development of a new type of functionalized implants.