Release Of Silver Ions Research Articles

A sol–gel based silver nanoparticle/polytetrafluorethylene (AgNP/PTFE) coating with enhanced antibacterial and anti-corrosive properties

In this research, a silver nanoparticle/polytetrafluorethylene (AgNP/PTFE) coating for metallic implants was fabricated using a facile layer-by-layer coating method. PTFE nanoparticles were immobilized in a sol–gel matrix and dip-coated onto 316L stainless steel via a mussel-inspired approach followed by AgNP deposition. Benefiting from the synergistic effect of antibacterial AgNP and non-stick PTFE, the AgNP/PTFE coating exhibited superior antibiofilm activity against Escherichia coli WT F1693 and enhanced corrosion resistance. Compared with surfaces only coated with PTFE, the AgNP/PTFE coated surfaces were capable of sustained release of silver ions, inhibiting up to ~50% bacterial biomass accumulation after 7 days. To understand the anti-adhesion mechanism, both classic DLVO and XDLVO theories were used to model and explain bacterial adhesion. Despite concerns that an over-release of silver ions may cause toxic effects towards mammalian cells, the coating procedures offered ease of control over the silver loading, making it potentially useful for preventing metallic implant-associated infections.

DNA damage and genetic aberration induced via different sized silver nanoparticles: Therapeutic approaches of Casimiroa edulis and Glycosmis pentaphylla leaves extracts.

Potential of Casimiroa edulis and Glycosmis pentaphylla leaves extracts were investigated against the effect of two different particle sizes of silver nanoparticles induced toxicity in mice. Mice received silver nanoparticles (AgNPs) (100mg/kg) with 20 and 100nm for four weeks followed by daily oral dose of extracts (500mg/kg) for three weeks. C. edulis leaves identified fourteen phenolic compounds while, G. pentaphylla leaves identified, twelve phenolic compounds. Additionally, biochemical, genotoxicity, mutagenicity, and histopathological investigations were carried out, revealed that liver function activities, lipid profile, hydrogen peroxide, and C-reactive protein were significantly elevate post AgNPs exposure. While, superoxide dismutase, glutathione-S-transferases, and glutathione peroxidase significantly reduce. A marked amelioration in all detected biomarkers, improved histopathological changes and repair DNA damage after treated with C. edulis and G. pentaphylla leaves extracts. These extracts are used for the first time as promising candidate therapeutic agents against toxicity induced by AgNPs. PRACTICAL APPLICATIONS: The potential applications of AgNPs make it necessary to investigate the possible toxicity associated with release of free silver ions in the biological system. AgNPs of varying particle sizes had toxic effects as evidenced by alterations in some cellular biochemical parameters, genotoxicity, mutagenicity, and histopathological indices on mice. Casimiroa edulis and Glycosmis pentaphylla leaves extracts are used for the first time as promising candidate therapeutic, where they are able to ameliorate the toxicity induced via AgNPs and record vacillate percentage of improvement in the selected biomarkers, as a result of the bioactive secondary metabolites especially flavonoids and other polyphenolic compounds.

Use of silver nanoparticles to counter fungicide-resistance in Monilinia fructicola

The potential of Ag-NPs to suppress Monilia fructicola isolates and to broaden the effectiveness of fungicides to overcome resistance was tested in vitro and in vivo. Twenty-three M. fructicola isolates were subjected to fungitoxicity screening with a number of fungicides in vitro, which resulted in the detection of 18 isolates resistant to benzimidazoles (BEN-R) thiophanare methyl (TM) and carbendazim (CARB). DNA sequencing revealed the E198A resistance mutation in the β-tubulin gene, target site of the benzimidazole fungicides in all resistant isolates. Ag-NPs effectively suppressed mycelial growth in both sensitive (BENS) and resistant isolates. The combination of Ag-NPs with TM led to a significantly enhanced fungitoxic effect compared to the individual treatments regardless resistant phenotype (BEN-R/S) both in vitro and when applied on apple fruit. The above observed additive/synergistic action is probably associated with an enhanced Ag-NPs activity/availability as indicated by the positive correlation between Ag-NPs and TM + Ag-NPs treatments. No correlation was found between AgNO3 and Ag-NPs suggesting that difference(s) exist in the fungitoxic mechanism of action between nanoparticles and their ionic counterparts. Synergy observed between Ag-NPs and the oxidative phosphorylation-uncoupler fluazinam (FM) against both resistance phenotypes indicates a possible role of energy (ATP) metabolism in the mode of action of Ag-NPs. Additionally, the role of released silver ions on the fungitoxic action of Ag-NPs against M. fructicola was found to be limited because the combination with NaCl revealed a synergistic rather than the antagonistic effect that would be expected from silver ion binding with chlorine ions. The results of this study suggested that Ag-NPs can be effectively used against M. fructicola and when used in combination with conventional fungicides they could provide the means for countering benzimidazole resistance and at the same time reduce the environmental impact of synthetic fungicides by reducing doses needed for the control of the pathogen.

Preclinical Study of a Multi-Layered Antimicrobial Patch Based on Thin Nanocomposite Amorphous Diamond Like Carbon Films with Embedded Silver Nanoparticles.

A growing number of severe infections are related to antibiotic-resistant bacteria, therefore, in recent years, alternative antimicrobial materials based on silver nanoparticles (NPs) attracted a lot of attention. In the current research, we present a medical patch prototype containing diamond-like carbon nanocomposite thin films doped with silver nanoparticles (DLC:Ag), as a source of silver ions, and an aqueous mass of the gelatin/agar mixture as a silver ion accumulation layer. The DLC:Ag thin films with 3.4 at.% of silver were deposited on synthetic silk employing reactive unbalanced DC magnetron sputtering of the silver target with argon ions performed in the acetylene gas atmosphere. The average size of the silver nanoparticles as defined by scanning electron microscope was 24 nm. After the film deposition, the samples were etched with RF oxygen plasma, aiming at efficient silver ion release in aqueous media from the nanocomposite film. In the patch prototype, a mixture of agar and gelatin was applied in silicone carrier with cavities, acting as a silver ion accumulation layer that further enhanced the antimicrobial efficiency. It was found that the DLC:Ag thin film on the silk after soaking in water for 24 h was able to release up to 4 ppm of Ag. The microbiological experiments using S. aureus bacteria were performed with the patch prototype and the silver ion saturated water, demonstrated the inactivation of 99% and 79% of bacteria, respectively. Scanning electron microscopy analysis showed that silver NPs destroyed the bacteria cell and the bacteria affected by Ag ions had spots and perforated cell wall areas with cytoplasm leakage out was obtained. A preliminary preclinical study using the laboratory animals demonstrated that using the patch prototype, the methicillin-resistant S. aureus (MRSA)-infected wound on skin surface healed faster compared with control and was able to kill all MRSA bacteria strains in the wound’s bed after 72 h of treatment.

Visible light plasmon excitation of silver nanoparticles against antibiotic-resistant Pseudomonas aeruginosa.

The interaction of metallic nanoparticles with light excites a local surface plasmon resonance (LSPR). This phenomenon enables the transfer of hot electrons to substrates that release Reactive Oxygen Species (ROS). In this context, the present study aimed at enhancing the antibacterial effect of citrate-covered silver nanoparticles (AgNPs) by LSPR excitation with visible LED. AgNPs possess excellent antimicrobial properties against Pseudomonas aeruginosa, one of the most refractory organisms to antibiotic treatment. The Minimum Inhibitory Concentration (MIC) of the AgNPs was 10 μg/ml under dark conditions and 5 μg/ml under light conditions. The combination of light and AgNPs led to 100% cell death after 60 min. Flow cytometry quantification showed that bacteria treated with LSPR-stimulated AgNPs displayed 4.8 times more ROS. This significant increase in ROS possibly accounts for most of the antimicrobial effect of the AgNPs. In addition, light exposition caused a small release of silver ions (0.4%) suggesting that silver ions may play a secondary role in P. aeruginosa death. Overall, the results presented here show that LSPR stimulation of AgNPs by visible light enhances the antimicrobial activity of silver nanoparticles and can be an alternative for the treatment of topic infections caused by antibiotic-resistant bacteria such as P. aeruginosa.

Design and Preparation of Silver–Copper Nanoalloys for Antibacterial Applications

The search for new more effective nanoparticles based antimicrobial agents has been under way in recent decades. Silver nanoparticles are hydrophobic and have a negative charge. We report on the preparation of Ag–Cu bimetallic nanoparticles with various silver contents synthesized by electric explosion of two twisted wires of the metals in argon atmosphere. The method allows to obtain nanoparticles of a given composition, has high performance and scalability. Nanoparticles were investigated using X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive analysis and microelectrophoresis techniques. We evaluated the antibacterial activity of the nanoparticles against Gram-negative E. coli and Gram-positive methicillin resistance S. aureus MRSA. Our study showed that the synthesized nanoparticles have a positive zeta potential of about 30 mV at pH 7.2 and high antimicrobial activity against the tested bacteria strains, which is close to the activity of silver nanoparticles with a size of 20 nm. The high antimicrobial activity of the nanoparticles is due to the prolonged slow release of silver and copper ions, which makes nanoalloys more effective than Cu and Ag metallic nanoparticles. The synthesized nanoparticles have high antimicrobial activity and demonstrate the potential for their use as promising new generation antibacterial agents effective against resistant microorganisms.

Polyimide with half encapsulated silver nanoparticles grafted ceramic composite membrane: Enhanced silver stability and lasting anti‒biofouling performance

To take advantage of Ag NPs‒enhanced membrane properties, how to slow the release of silver ions from membrane surface is the key. In this study, to enhance silver stability, half encapsulated Ag NPs by a loosely polyimide (PI) were covalently grafted onto ceramic membrane (CM) via in-situ reduction during thermal imidization. Various techniques were used to characterize the micro‒structure, pore size distribution, surface tension, and Zeta potential of the polyimide‒silver nanoparticle‒ceramic composite membrane (PI–Ag/CM). The antibacterial activity was assessed with fluorescent imaging method. The stability of silver was evaluated by static immersion and dynamic filtration tests. The anti‒biofouling performance was evaluated using bovine serum albumin (BSA) and E. coli as the model foulants, respectively. The results showed that the Ag NPs with the size of 50–80 nm were uniformly embedded on the surface of the grafted PI, which endowed the PI‒Ag/CM with improved silver stability, antibacterial activity, and anti‒biofouling performance simultaneously. This study demonstrated a new pathway for the modification of CM‒based and other inorganic membranes with lasting anti‒biofouling performance in water treatment.

Fabrication of Microporous Coatings on Titanium Implants with Improved Mechanical, Antibacterial, and Cell-Interactive Properties.

The success of an orthopedic implant therapy depends on successful bone integration and the prevention of microbial infections. In this work, plasma electrolytic oxidation (PEO) was performed to deposit TiO2 coatings enriched with Ca, P, and Ag on titanium to improve its surface properties and antibacterial efficacy while maintaining normal biological functions and thus to enhance the performance of orthopedic implants. After PEO treatment, the surface of Ti was converted to anatase and rutile TiO2, hydroxyapatite, and calcium titanate phases. The presence of these crystalline phases was further increased with an increased Ag content in the coatings. The developed coatings also exhibited a more porous morphology with an improved surface wettability, roughness, microhardness, and frictional coefficient. In vitro antibacterial assays indicated that the Ag-doped coatings can significantly prevent the growth of both Staphylococcus aureus and Escherichia coli by releasing Ag+ ions, and the ability to prevent these bacteria was enhanced by increasing the Ag content in the coatings, resulting in a maximal 6-log reduction of E. coli and a maximal 5-log reduction of S. aureus after 24 h of incubation. Moreover, the in vitro cytocompatibility evaluation of the coatings showed that the osteoblast (MC3T3) cell integration on the PEO-based coatings was greatly improved compared to untreated Ti and no notable impact on their cytocompatibility was observed on increasing the amount of Ag in the coating. In conclusion, the coating with favorable physicochemical and mechanical properties along with controlled silver ion release can offer an excellent antibacterial performance and osteocompatibility and can thus become a prospective coating strategy to face current challenges in orthopedics.

Combining Ag and γ-Fe2O3 properties to produce effective antibacterial nanocomposites

The antibacterial activity of hybrid γ-Fe2O3/Ag nanocomposites against the bacterial pathogens E. coli (Gram-negative) and S. aureus (Gram-positive) has been studied. Silver is a well-known bactericidal agent and γ-Fe2O3 nanoparticles release heat when they are exposed to alternating magnetic fields. The combination of both properties to fight infections has not been previously explored. The nanocomposites were synthesized through reduction of silver nitrate in the presence of pre-synthesized superparamagnetic γ-Fe2O3 nanoparticles. Changing systematically the ratio of γ-Fe2O3 and silver precursor and the temperature of the reaction allowed obtaining superparamagnetic nanocomposites with different Ag contents and particle sizes. The antibacterial activity of the samples was tested, and the minimum inhibitory concentrations and minimum bactericidal concentrations of the nanocomposites were determined to compare the microbicidal activity of the samples. It was found that it is related with the release of silver ions from the nanocomposites. Finally, we studied the combination of the bactericidal effect of silver and magnetic hyperthermia finding a synergetic effect between them when plates containing E. coli or S. aureus bacteria with γ-Fe2O3/Ag nanocomposites were subjected to an alternating magnetic field. This effect is related with an increase in the release of silver ions due to that heat dissipation.

Dental Materials Incorporated with Nanometals and Their Effect on the Bacterial Growth of Staphylococcus aureus.

PurposeThe purpose of this study was to investigate the effect of different commercially used dental materials (RelyX Luting Plus and Dyract Extra) mixed with either a metallic ionic solution or a colloidal suspension of metallic nanoparticles. Both the solution and the suspension contained a mixture of silver, copper, and lithium ions.MethodsThe metal/ion-incorporated dental materials were prepared into disk-shaped samples and tested against the growth of Staphylococcus aureus. The susceptibility of bacteria against the antibacterial dental disks was tested using two methods: counting the colony-forming units per milliliter and disk diffusion (Kirby–Bauer). The incorporated materials (Dyract and Rely cement) were tested for ion release using flame atomic absorption spectroscopy.ResultsAssessment showed efficient antibacterial activity of metal ion–incorporated Rely luting cement, exhibited by the formation of inhibition zones larger than those formed by the standard antibiotic, as well as a reduction in bacterial number of sevenfold after incubation for 24 hours. Dyract material incorporated with nanoparticles showed no significant clear zones and had no inhibiting effect on bacterial colony numbers after incubation for 24 hours. The release of silver, copper, and lithium metal ions depended on the type of both dental material and the incorporated nanoagents. The metal ion–incorporated Rely Plus cement released the highest levels of metal ions, which was attributed to its antibacterial efficiency.ConclusionRely Plus cement incorporated with the nanoparticle suspension demonstrated high antibacterial potency, due to the release of the highest concentrations of silver, copper, and lithium metal ions. This work is the first direct comparative study of dental materials with different forms of nanomixtures (metallic nanoparticles and soluble metallic ions) and their antibacterial effects after incubation with bacterial culture for 24 hours.

Antibacterial Activity of Mesoporous Silica Nanofibers

In this research, the fabrication of MCM-41 mesoporous material nanofibers by an electrospinning technique was performed. The MCM-41 nanofibers (MCM-41 NFs) as a novel host on the incorporation of silver has been studied in [Ag(NH3)2]NO3 precursor solution through the heat-treatment process. The formation of silver-loaded MCM-41 NFs at various calcinating temperatures were also studied. The silver-containing materials (Ag/MCM-41 NFs) were characterized using Fourier Transform InfraRed (FT-IR) spectroscopy, powder X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UltraViolet-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS), and Transmission Electron Microscopy (TEM). The results indicated that both Ag and Ag2O NanoParticles (NPs) were loaded in MCM-41 NFs at different calcinating temperature. Silver compounds with a diameter of 10−15 nm were highly dispersed in the framework of mesoporous silica nanofibers. The results indicated that Ag loading contents on the MCM-41NFs were 10.53 wt%. These Ag/MCM-41 NFs Possess an enhanced antibacterial effective against both Gram-positive and Gram-negative bacteria by preventing the aggregation of silver NPs and continuously releasing silver ions. In general, the silver-containing materials with more Ag2O NPs demonstrated an excellent antibacterial activity. The Minimum Inhibitory Concentrations (MIC) obtained 30 and 60 µg/mLfor the silver-containing MCM-41 NFs with more Ag2O NPs against E. coli and S. aureus, respectively. MCM-41 type nanofibers play an important role in the antibacterial activity of nanocomposites.

Synthesis and antibacterial activity of cellulose acetate sheets modified with flower-shaped AlOOH/Ag

Modified cellulose acetate antibacterial material was obtained by immobilizing Al/Ag nanoparticles on fabric fibres in water and subsequent hydrolysis of this nanoparticles under mild reaction condition. AlOOH/Ag self-assembled flower-shaped nanostructures consist of AlOOH nanoplates and Ag inclusions. The AlOOH nanosheets size is of 150–300 nm, thickness is 5–7 nm. The silver inclusions were from 5 to 30 nm in size. Flower-shaped AlOOH/Ag nanostructures change the charge of fibres and stabilize Ag nanoparticles against agglomeration. The positive charge of the modified fibres improves the bacteria adsorption due to electrostatic interaction. The antibacterial activity of the nanoparticles and modified material arise due to the slow Ag+ migration into the medium from stabilized Ag nanoparticles. The nanoparticles and modified cellulose acetate sheets were characterized by transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction analysis, FTIR spectroscopy. The release of silver ions to the medium remains low for 70 h with AlOOH/Ag@CA reducing all the tested bacterial strains below the limit of detection (102 CFU/mL) within 3 h for Escherichia coli and 6 h for MRSA due to local effects of silver on adsorbed bacteria. The antibacterial activity of modified cellulose acetate fabric allows this method of modification to be exploited to produce materials for biomedical applications.

Facile synthesis, antibacterial mechanisms and cytocompatibility of Ag–MnFe2O4 magnetic nanoparticles

Magnetic MnFe2O4 nanoparticles containing 0, 1 and 3 at.% silver, respectively were synthesized by one-pot sol-gel method for antibacterial applications in biomedical fields. Material characterizations indicate that MnFe2O4 begins crystallization at 134 °C and oxidation at 450 °C, the grain size and agglomeration degree increase with the silver content and silver exists as metallic state for the particles. The saturation magnetization decreases with the sintering temperature and slightly increases with the silver content, with the maximum of 50.0 emu/g obtained. Antibacterial tests by plate counting and PI-Hoechst 33342 staining suggest that the antibacterial activity of Ag–MnFe2O4 nanoparticles is silver content-dependent. Silver ions concentration measurement, β-galactosidase activity assay and transmission electron microscopic observation show that the antibacterial activity is dominated by the actions of the released silver ions, rather than the membrane cell impairment or reactive oxygen species-induced oxidative stress mechanism. MC3T3-E1 cell test demonstrates the best cytocompatibility of the nanoparticles with 3 at.% silver, which is likely related to the reduced cell endocytosis of the aggregated particles. The combination of magnetism, antibacterial activity and biocompatibility would make Ag–MnFe2O4 nanoparticles a potential multi-functional material in various biomedical applications.

Antibacterial Effects of Bimetallic Clusters Incorporated in Amorphous Carbon for Stent Application.

The purpose of this work is the development of Ag/a:C and Ag-Au/a:C coatings for ureteral stents, to provide them with antimicrobial characteristics. Silver was selected because of its well-known antibacterial properties, while gold was included to assess its capacity to accelerate the silver ion release forming a galvanic couple between Au and Ag. Thus, the metallic (Ag) and bimetallic clusters (Ag-Au) were produced by three different configurations: (i) unbalanced magnetron sputtering (conventional sputtering), (ii) plasma gas condensation process, and by (iii) a combination between both previous approaches. Coatings with Ag-Au bimetallic clusters were characterized by transmission electron microscopy (TEM) in order to study the arrangement (alloy, core-shell, and galvanic couple) of these particles in the carbon matrix. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to quantify the Ag ions released through artificial urine from the different coatings deposited on thermoplastic polyurethane tape (one of the materials used in the manufacture of the ureteral stent ). Then, the antibacterial and cytotoxicity properties of Ag and Ag-Au/a:C coatings were evaluated. TEM shows that a biphasic structure was not detected, thus not allowing to anticipate the establishment of a galvanic couple. The ICP-OES results demonstrate that the silver ionization is mainly a function of the amount of silver incorporated in the amorphous carbon (a:C) matrix, and the formation of a bimetallic alloy has a detrimental effect on release of the silver ions. The antibacterial activity was regulated by the silver ionization mechanisms because the coatings with higher Ag release had a higher antibacterial activity.

Silver nanoparticles induce size-dependent and particle-specific neurotoxicity to primary cultures of rat cerebral cortical neurons.

Silver nanoparticles (AgNPs) are widely applied in many fields because of their excellent antibacterial activities. Toxicological studies have showed that AgNPs can cross the blood-brain barrier and exhibit high retention in the brain. Therefore, the potential neurotoxicity of AgNPs is raising serious concerns. This study investigated the neurotoxicological effects of AgNPs with two different sizes (20nm and 70nm, AgNPs-20 and AgNPs-70) using primary cultures of rat cerebral cortical neurons in mature and developing stages. The contribution of silver ion release was investigated by testing the effects of ionic silver in parallel. The results showed that both AgNPs-20 and AgNPs-70 significantly decreased neuronal cell viability, and AgNPs-20 had stronger toxicity compared with AgNPs-70. AgNP applications caused the granulated skeleton structure of the mature neurons with some broken synapses after a 24-h exposure, and inhibited neuronal growth during a 7-day exposure. Intracellular silver accumulation at non-cytotoxic exposure levels inhibited dopamine efflux, which was particle-specific and free of released silver ions. The findings herein can aid in guiding the proper applications of AgNPs in different areas, especially in medical use.

Silver nanoparticles and silver ions cause inflammatory response through induction of cell necrosis and the release of mitochondria in vivo and in vitro.

Owing to the excellent antibacterial and antiviral activity, silver nanoparticles have a widespread use in the food and pharmaceutical industries. With the increase in the production and use of the related products, the potential hazard of silver nanoparticles has aroused public attention. The main purpose of this study is to explore the toxicity of silver nanoparticles and induction of lung inflammation in vitro and in vivo. Here, we validated that small amounts of silver ions dissolved from silver nanoparticles caused the depolarization of plasma membrane, resulting in an overload of intracellular sodium and calcium, and eventually led to the cell necrosis. The blockers of calcium or sodium channels inversed the toxicity of silver ions. Then, we instilled silver nanoparticles or silver nitrate (50μg per mouse) into the lungs of mice, and this induced pulmonary injury and mitochondrial content release, led to the recruitment of neutrophils to the lung tissue via p38 MAPK pathway. Altogether, these data show that released silver ions from nanoparticles induced cell necrosis through Na+ and Ca2+ influx and triggered pulmonary inflammation through elevating mitochondrial-related contents released from these necrotic cells.

Atmospheric-Pressure Plasma Spray Deposition of Silver/HMDSO Nanocomposite on Polyamide 6,6 with Controllable Antibacterial Activity

Novel coatings containing silver nanoparticles (AgNPs) with strong bonding and controllable antibacterial activity on polyamide 6,6 fabric were produced by dielectric barrier discharge (DBD) plasma-assisted deposition at atmospheric pressure and hexamethyldisiloxane (HMDSO) layers. Silver ion release was tuned using a "sandwich" coating structure to prolong the antibacterial effect. The novel spray-assisted deposition increased deposition rates of AgNPs using atmospheric pressure DBD plasma treatment when an HMDSO layer was applied. An increase in AgNPs deposition in plasma treated samples and antimicrobial activity against Gram-negative (Escherichia coli) for samples with an additional HMDSO layer was observed. These coatings allow the development of new and safe wound dressings able to switch the antimicrobial effect against Gram-positive and Gram-negative bacteria by washing the dressing at high temperature (75 °C) before application.

The Antibacterial Mechanism of Silver Nanoparticles and Its Application in Dentistry.

Nanotechnology has recently emerged as a rapidly growing field with numerous biomedical science applications. At the same time, silver has been adopted as an antimicrobial material and disinfectant that is relatively free of adverse effects. Silver nanoparticles possess a broad spectrum of antibacterial, antifungal and antiviral properties. Silver nanoparticles have the ability to penetrate bacterial cell walls, changing the structure of cell membranes and even resulting in cell death. Their efficacy is due not only to their nanoscale size but also to their large ratio of surface area to volume. They can increase the permeability of cell membranes, produce reactive oxygen species, and interrupt replication of deoxyribonucleic acid by releasing silver ions. Researchers have studied silver nanoparticles as antimicrobial agents in dentistry. For instance, silver nanoparticles can be incorporated into acrylic resins for fabrication of removable dentures in prosthetic treatment, composite resin in restorative treatment, irrigating solution and obturation material in endodontic treatment, adhesive materials in orthodontic treatment, membrane for guided tissue regeneration in periodontal treatment, and titanium coating in dental implant treatment. Although not all authorities have acknowledged the safety of silver nanoparticles, no systemic toxicity of ingested silver nanoparticles has been reported. A broad concern is their potential hazard if they are released into the environment. However, the interaction of nanoparticles with toxic materials and organic compounds can either increase or reduce their toxicity. This paper provides an overview of the antibacterial use of silver nanoparticles in dentistry, highlighting their antibacterial mechanism, potential applications and safety in clinical treatment.

Facile preparation of organic-inorganic hydrogels containing silver or essential oil with antimicrobial effects

Hydrogels (HGs) based on Poly-(vinyl)alcohol (PVA), sodium alginate (SA) and borax were appropriately modified with both poly(ethylene)oxide (PEO) and ZnAl layered double hydroxide (LDH) to create a network in which active molecules can be loaded and confined. PEO acts as a porogen agent in the PVA matrix, reducing the crosslinking degree of the polymer and favouring the retention of organic apolar species. LDH, in nitrate or chloride form, organically modified with SA (LDH/N@SA and LDH/C@SA), reinforces the polymeric network, improving its mechanical properties. Moreover, LDH/N@SA and LDH/C@SA were used to grow and anchor nanoparticles of Ag and Ag/AgCl, becoming fillers of HGs containing active species. An additional sample was prepared by incorporating thyme essential oil (EO) in a HG prepared with LDH/C@SA. These systems provided a sustained release of silver ions and EO and a very efficient swelling in water. The HGs subjected to antimicrobial tests, exhibited good antimicrobial activity against both Gram-positive (Staphylococcus epidermidis and S. aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria and yeast (Candida albicans). These characteristics make the HGs suitable to be proposed as patches for wound healing.

Polyelectrolyte multilayer coatings for short/long-term release of antibacterial agents

Osteomyelitis caused by orthopedic and cranial implants infection is the principal cause of implant failure, septicemia, and even death; it is an urgent issue with prevalence rates ranging from 4% to 10% in industrialized countries. Bioactive and multifunctional materials such as bioglass, biometal, and biopolymer are commonly used in biomedical fields; however, it is still a challenge to fabricate effective antibacterial coatings. The purpose of this study is to use layer-by-layer technology to develop an antibacterial coating with outer and inner portions for short/long-term release of antibacterial agents. Antibiotics would be released immediately after implant and antibacterial silver ions in the long term. In this study, polyelectrolyte multilayers (PEMs) comprised of collagen as the cationic layers and γ-poly-glutamic acid as the anionic layers were coated onto the 316L stainless steel substrate via a spin coating technique. A chitosan buffer layer was designed and placed in the middle of the coating. 1 mol% silver additive 58S bioactive glass (SiO2: CaO: P2O5 = 60: 36: 4 in mol%) was introduced into the inner γ-poly-glutamic acid layers, while gentamicin was added to the outer layer.Herein, it is demonstrated that bioactive glass was successfully incorporated into the PEM coatings which had a total thickness of about 61.4 ± 2.8 μm (via SEM) and good hydrophilicity with a contact angle of 34.91°. The PEMs had a hardness of 0.18 ± 0.02 GPa, Young's modulus of 3.85 ± 0.32 GPa, and roughness of 394.7 nm. In the short-term, the PEM coatings would release gentamicin and silver ions, while the long-term controlled release of silver ions served as an antibacterial. The PEM coatings were not only effective as an antibacterial, as seen in the zone of inhibition test, but also biocompatible with rat bone marrow mesenchymal stem cells (BMSCs), as seen in the MTT assay. Therefore, we believe that this technology will have great potential in the surface modification of orthopedic and cranial implants due to its antibacterial, tissue restoration, and osseointegration properties.