Release Of Silver Ions Research Articles

Rapid release of high-valent silver ions from water-soluble porphyrin complexes to enhance the direct killing of Methicillin-Resistant Staphylococcus aureus

The emergence of multidrug-resistant (MDR) bacteria represented by MRSA (Methicillin-resistant Staphylococcus aureus) poses a great challenge to current anti-infection treatment. It is critical to develop efficient MRSA anti-bacteria drugs and explore simple therapeutic strategies with low MDR risk. Herein, we synthesized high-valent (AgII/AgIII) water-soluble porphyrins (cationic AgTMPyP and anionic AgTMPPS) and investigated their direct bactericidal property for MRSA without photoactivation in vitro and in vivo. The cationic porphyrin AgTMPyP exhibits well oxidase-like activity and has 100% sterilizing rate at 8 μmol/L concentration. Besides, AgTMPyP can effectively destroy biofilms in vitro, mediate the polarization of macrophages from M1 to M2, and promote wound healing in vivo. Combined with DFT calculation, the related antibacterial mechanism is further discussed. High-valent silverporphyrins can maintain stable in water for at least 200 days. The moment they encounter MRSA, high-valent silver ions from AgTMPyP can be immediately released from the porphyrin ring and attack the MRSA with efficient sterilization. Together with the hemolysis, blood routine and blood biochemistry tests, it is proved that AgTMPyP can have great prospects in the direct treatment of bacterial infections in skin diseases in the future. Statement of significance: The emergence of multidrug-resistant (MDR) bacteria represented by MRSA poses a great challenge to current anti-infection treatment. It has become critical to develop efficient MRSA anti-bacteria drugs and explore simple therapeutic strategies with low MDR risk. We synthesized high-valent (AgII/AgIII) water-soluble silver porphyrins (AgTMPyP and AgTMPPS), which can be stable for long periods in aqueous solutions. AgTMPyP can directly and efficiently kill bacteria and destroy biofilms without photoactivation in vitro and in vivo. Combined with DFT calculation, the related antibacterial mechanism is further discussed. AgTMPyP is a superior antimicrobial agent with good biocompatibility and it can have great prospects in the direct treatment of bacterial infections and wound healing in the future.

Green Synthesis of Silver Nanoparticles (CM-AgNPs) from the Root of Chuanminshen for Improving the Cytotoxicity Effect in Cancer Cells with Antibacterial and Antioxidant Activities

The unique properties of silver nanoparticles (AgNPs), such as size, surface charge, and the ability to release silver ions, contribute to DNA damage, inducing of oxidative stress, and apoptosis in cancer cells. Thus, the potential application of AgNPs in the field of biomedicine, and cancer therapy are rapidly increasing day by day. Therefore, in this study, AgNPs were synthesized by extract of Chuanminshen violaceum, and then the synthesized CM-AgNPs were fully characterized. The biological activity of CM-AgNPs was investigated for antibacterial, antioxidant, and anticancer activities. The cytotoxic activity of CM-AgNPs was tested for various kinds of cancer cells including MKN45 gastric cancer cells, HCT116 human colon cancer cells, A549 human lung cancer cells, and HepG2 liver cancer cells. Among these cancer cells, the induced apoptosis activity of CM-AgNPs on HCT116 cancer cells was better and was used for further investigation. Besides, the CM-AgNPs exhibited great antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) with 50% free radical scavenging activity, and CM-AgNPs also showed a significant antibacterial activity against Escherichia coli and Staphylococcus aureus. Thus, our pilot data demonstrated that the green synthesis of CM-AgNPs would be considered a good candidate for the treatment of HCT116 cancer cells, with its strong antioxidant activity and antibacterial effects.

Exploring the Efficacy of pH-Responsive Vancomycin/Ag/ZIF-8 Nanoparticles Modified with Hyaluronic Acid for Enhanced Antibacterial Therapy and Wound Healing.

This study introduces a novel type of metal-organic framework material, specifically zeolitic imidazolate framework-8 (ZIF-8), that is integrated with silver nanoparticles and further enhanced by incorporating vancomycin (Van) to create a composite named as Van/Ag/ZIF-8. This composite demonstrates a potent and smart antimicrobial effect due to its ability for releasing silver ions and Van in a controlled manner, especially in the microacidic conditions surrounding bacterial cells. Furthermore, we used hyaluronic acid to modify Van/Ag/ZIF-8, resulting in a composite denoted as Van/Ag/ZIF-8@HA. This composite exhibits a significant inhibition effect against the proliferation of both Gram-negative (Escherichia coli 100%) and Gram-positive (Staphylococcus aureus 99.9%) resistant bacterial strains while exerting no adverse effects on animal cellular growth. These findings underscore its favorable biocompatibility profile. The experimental results show a combined antibacterial action against prevalent bacterial infections, which is supported by in vivo experiments using a skin wound model. This work confirms the composite's significant role in fighting pathogenic infections and aiding in healing skin wounds. The innovative strategy not only tackles the pressing issue of antibiotic-resistant bacterial infections but also marks a significant advancement in the areas of wound healing and medical research, offering a promising path for future investigations and therapeutic uses.

Novel biocompatible magnetron-sputtered silver coating for enhanced antibacterial properties and osteogenesis in vitro

Peri-implant infection is a serious complication in orthopedic surgery. This study aimed to reduce the incidence of peri-implant infection by developing a durable and safe antibacterial silver coating. We compared the antibacterial properties and process controllability of various coating techniques to identify the most effective method for silver coating. We refined substrate treatment techniques and coating thicknesses through antibacterial and scratch tests. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to analyze the coating’s morphology and composition. Micron-sized magnetron sputtering silver coating samples underwent in vitro antibacterial testing, cytotoxicity testing, silver ion release testing, and osteogenic testing using membrane contact culture, CCK-8 assay, inductively coupled plasma (ICP) detection, and alkaline phosphatase (ALP) activity/osteogenic gene PCR. Magnetron sputtering demonstrated superior antibacterial properties, uniformity, and process controllability compared to alternative techniques. The optimal adhesion strength was achieved with a 0.5 μm coating thickness and a 400 mesh sandpaper pretreatment process, without compromising antibacterial efficacy. The coating showed near-perfect antiseptic results in antibacterial and anti-biofilm tests. Fibroblasts cultured in silver ion precipitation medium exhibited growth rates of 89% on day 30 and 88% on day 90, compared to 95% in the control group. The osteogenic test indicated that the magnetron sputtering silver coating promotes osteogenesis effectively. Our study demonstrated that micron-sized magnetron sputtering silver coating has potential for clinical use to prevent peri-implant infections in the future.

Biotechnological potential of silver nanoparticles synthesized by green method to control phytopathogenic bacteria: contributions from a proteomic analysis.

Silver nanoparticles (AgNPs) synthesized through green synthesis routes are widely used as antimicrobial agents due to their advantages such as biocompatibility, stability, sustainability, speed and cost-effectiveness. Although AgNPs appear to be more potent than silver ions, the mechanisms related to their antibacterial activity are not yet fully understood. The most common proposed mechanism of AgNPs' toxicity so far is the release of silver ions and/or specific functions of the particles. In this context, the present study aimed to investigate the mechanisms of action of AgNPs synthesized using noni fruit peels (Morinda citrifolia) against the phytopathogen Xanthomonas campestris pv. campestris (Xcc) through proteomics. Xcc was treated with AgNPs (32 µM), AgNO3 (32 µM), or received no treatment (Ctrl - control condition), and its proteomic response was comprehensively characterized to elucidate the antimicrobial mechanisms of AgNPs in the phytopathogenic microorganism. A total of 352 differentially abundant proteins were identified. Most proteins were regulated in the AgNPs × Ctrl and AgNPs × AgNO3 comparisons/conditions. When Xcc treated with 32 µM AgNPs were compared to controls, the results showed 134 differentially abundant proteins, including 107 increased and 27 decreased proteins. In contrast, when Xcc treated with 32 µM AgNO3 were compared to Ctrl, the results showed only 14 differentially abundant proteins, including 10 increased proteins and 4 decreased proteins. Finally, when Xcc treated with 32 µM AgNPs were compared to Xcc treated with 32 µM AgNO3, the results showed 204 differentially abundant proteins, including 75 increased proteins and 129 decreased proteins. Gene ontology enrichment analysis revealed that most of the increased proteins were involved in important biological processes such as metal ion homeostasis, detoxification, membrane organization, metabolic processes related to amino acids and carbohydrates, lipid metabolic processes, proteolysis, transmembrane transport, and others. The AgNPs used in this study demonstrated effective antimicrobial activity against the phytopathogenic bacteria Xcc. Furthermore, the obtained results contribute to a better understanding of the mechanisms of action of AgNPs in Xcc and may aid in the development of strategies to control Xcc in brassica.

Exploration of Metal Ion Release from Nickel-Chromium Denture Material: The Role of Saliva pH and Immersion Duration

Nickel chromium (NiCr) is a fixed denture material. Nickel has good physical, and mechanical properties, cheap, but it has low corrosion resistance. One way to increase corrosion resistance is to modify the metal surface by silver plating using the electroplating method. This study examines the effect of saliva pH and immersion time of NiCr metal with silver plating on the release of nickel, chromium, and silver ions. Laboratory experimental studies were 27 samples of NiCr with silver plating (Ø= 10 x 10 x 2 mm) immersed in saliva and divided into 9 groups (n=3): group I (pH 5 for 5 days), group II (pH 7 for 5 days), group III (pH 9 for 5 days), group IV (pH 5 for 10 days), group V (pH 7 for 10 days), group VI (pH 9 for 10 days), group VII (pH 5 for 15 days), group VIII (pH 7 for 15 days), group IX (pH 9 for 15 days). Nickel, chromium, and silver ions release was measured using atomic absorption spectrophotometry. The data obtained were analyzed using two-way ANOVA and post hoc LSD with a 95% confidence level (α =0.05). The results showed a significant difference between salivary pH and immersion time on the ion release (p<0.05). The release of nickel and silver ions increases at acidic pH, while the release of chromium ions increases at alkaline pH. Prolonged immersion (for 15 days) in saliva increases the release of nickel and chromium ions but decreases the release of silver ions.

In Silico SwissADME Analysis of Antibacterial NHC–Silver Acetates and Halides Complexes

This study investigates the antibacterial N-heterocyclic carbene (NHC)–silver complexes using the SwissADME platform, a web-based tool developed by the Swiss Institute of Bioinformatics (SIB). NHCs, particularly their silver complexes, have gained significant interest in medicinal chemistry for their potential as antibacterial and anticancer agents. The effectiveness of these complexes is closely linked to their structure, including factors like lipophilicity, which enhance their ability to penetrate bacterial cells and sustain the release of active silver ions. SwissADME provides computational estimates of pharmacokinetic properties, including absorption, distribution, metabolism, and excretion (ADME) characteristics, as well as drug-likeness and toxicity assessments. By evaluating parameters like molecular weight, topological polar surface area, lipophilicity (LogP), and water solubility, SwissADME offers insights into the drug-like potential of compounds. This study is inspired by a comprehensive review of antibacterial NHC–silver complexes published from 2006 to 2023, which identified superior structures with notable biological activity. The primary aim is to determine whether these active complexes exhibit distinct SwissADME parameters compared to others, providing a deeper understanding of the factors that influence their biological efficacy and aiding in the identification of promising drug candidates. Finally, experimental stabilities of exemplary complexes were confronted with absolute LUMO values derived from DFT calculations.

Silver-quercetin-loaded honeycomb-like Ti-based interface combats infection-triggered excessive inflammation via specific bactericidal and macrophage reprogramming

Excessive inflammation caused by bacterial infection is the primary cause of implant failure. Antibiotic treatment often fails to prevent peri-implant infection and may induce unexpected drug resistance. Herein, a non-antibiotic strategy based on the synergy of silver ion release and macrophage reprogramming is proposed for preventing infection and bacteria-induced inflammation suppression by the organic-inorganic hybridization of silver nanoparticle (AgNP) and quercetin (Que) into a polydopamine (PDA)-based coating on the 3D framework of porous titanium (SQPdFT). Once the planktonic bacteria (e.g., Escherichia coli, Staphylococcus aureus) reach the surface of SQPdFT, released Que disrupts the bacterial membrane. Then, AgNP can penetrate the invading bacterium and kill them, which further inhibits the biofilm formation. Simultaneously, released Que can regulate macrophage polarization homeostasis via the peroxisome proliferators-activated receptors gamma (PPARγ)-mediated nuclear factor kappa-B (NF-κB) pathway, thereby terminating excessive inflammatory responses. These advantages facilitate the adhesion and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs), concomitantly suppressing osteoclast maturation, and eventually conferring superior mechanical stability to SQPdFT within the medullary cavity. In summary, owing to its excellent antibacterial effect, immune remodeling function, and pro-osteointegration ability, SQPdFT is a promising protective coating for titanium-based implants used in orthopedic replacement surgery.

Preparation and characterization of Ea-AgNPs-Si nanocomposite: investigating it as a poultry reformer, pathogen suppressor, sprouting catalyst and adsorbent

This study synthesizes nano composite (Ea-AgNPs-Si) using Euphorbia antisyphilitica(Ea), employing it as a poultry reformer, sorptive material, pathogen suppressor and sprouting catalyst. Characterization involved XRD, SEM, TEM, Zetasizer, UV-Visible and FT-IR techniques. Ea-AgNPs-Si adopted a face centered cubic arrangement with average crystalline size of 20.34 nm. Zeta potential assessed stability. PDI value of Ea-AgNPs-Si nanocomposite is 1 indicating the polydisperse distribution. SEM revealed flower shape (Ea-AgNPs-Si), ranging 70-100 nm in diameter. The disc diffusion method reveals that EaAgNPs-Si exhibits potent antimicrobial activity at 60 µl against Staphylococcus aureus, Actinomycetes, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa, attributed to its deep diffusion and release of silver ions and silica. It is unequivocally evident from the data that Langmuir isotherm and Pseudo II order model provides a superior fit approaching R2 value as 0.9972, 0.9461, 0.916, 0.9827, 0.9455 and 0.9534 for LA(I), LA(II), LA(III) describing monolayer chemisorption onto surfaces with uniform adsorption energies than Freundlich, Tempkin and BET models, which is synonymous with the results obtained from R2011a Matlab neuro solution. Through final germination (FG) we concluded that among 130 corriandrum seeds sown,109 sprouted in 20 days. Higher germination index (GI) T2>T4>T1>T3> expedited that Ea-AgNPs-Si shall be used as a nutrient to boost the growth of crops. Ordinarily, it necessitates a span of 45 days for a single batch to attain harvest readiness; however, through our efforts, we have accomplished this feat in a mere 20 days. Henceforth, Ea-AgNPs-Si shall be employed as a Poultry Reformer, Pathogen Suppressor, Sprouting Catalyst and Adsorbent.

A novel antibacterial and wear-resistant strategy based on metal surface micro-texture nitriding coupled functional mesoporous silicon coating

Modified metal layers coupling durable antifouling and antibacterial properties have garnered considerable interest in various fields, including but not limited to medical equipment, kitchen utensils, public facilities, and specific industrial applications, such as transportation, energy utilization, and aerospace. Nevertheless, wear and corrosion resulting from harsh operating environments can significantly compromise the modified metal layers, leading to diminished antifouling and antibacterial capabilities. Currently, maintaining excellent antibacterial properties on the surface of metal-modified layers under complex working conditions remains a key challenge for metal protection technology. Herein, we innovatively propose a ternary collaborative strategy to optimize and extend the antifouling and antibacterial activity of metal substrate surfaces. Firstly, laser surface texturing (LST) is used to create micro-textured topography on the metal surface to serve as a reservoir for collecting debris and storing functionalized nanoparticles. Then, the surface micro-textures are treated with plasma nitriding to form a wear-resistant passivation layer that protects the aforementioned microstructures. Finally, a lubricant containing functional mesoporous silicon nanoparticles (Ag2O-MSNs@OTES) is coated on the metal surface, which not only reduces the friction coefficient but also achieves antibacterial and antifouling effects by continuously releasing silver ions from the mesoporous silicon spheres. Employing the aforementioned ternary coordination strategy, the fabricated coupling layer exhibits not only exceptional antifriction and wear properties but also remarkable antibacterial efficacy against both E. coli and S. aureus, attributed to the Ag2O-MSNs@OTES. Therefore, the wear-resisting and antibacterial coupling layer for the protection of metal surfaces has promising and versatile applications in wide areas.

Syntheses and antimicrobial activities of two coordination polymers assembled with Ag[sbnd]N and Ag[sbnd]O bonds

Two new coordination polymers ({[Ag(p-phda)2](BF4)} n (1) and {[Ag2(1,5-nds)(DMSO)2] DMSO}n (2) (p-phda: p-phenyldiacetonitrile, 1,5-nds: 1,5-naphthalene disulfonic acid, DMSO: dimethyl sulfoxide) were synthesized and characterized by IR, EA,TG and X-ray single crystal diffraction. 1 was revealed as a 2D “fishing net” assembled by AgN bonds with BF4− as equilibrium charge. IR and PXRD analysis showed the BF4− can be irreversibly exchanged by six anions varied in atomic numbers, sizes, configurations and coordination abilities. 2 is constructed by AgO bonds where DMSO function both as guest and bridging ligand. Further diffusion of NO into the solution of 1 and 2 generated two new compounds (1′ and 2′). All four compounds showed excellent broad-spectrum antimicrobial activities against gram-negative bacteria, gram-positive bacteria and yeast. The stronger antibacterial abilities of 1 against S. aureus and P. aeruginosa than those of 2 were evidenced by the smaller minimum inhibitory concentrations of silver ions (AgMICs) and the higher silver ion release rate in aqueous solution. It was concluded that the looser packing of 1 facilitate the silver ions releasing and play a more crucial role than binding mode and ligand-exchangeability. The enhanced P. aeruginosa inhibitions of 1′ and 2′ were elementarily ascribed to NO incorporation, supporting by their increased diameter of inhibition zones and decreased AgMICs.

Surface Charge-Modulated Toxicity of Cysteine-Stabilized Silver Nanoparticles.

The toxicity of silver nanoparticles (AgNPs) depends on their physicochemical properties. The ongoing research aims to develop effective methods for modifying AgNPs using molecules that enable control over the processes induced by nanoparticles in both normal and cancerous cells. Application of amino acid-stabilized nanoparticles appears promising, exhibiting tunable electrokinetic properties. Therefore, this study focused on determining the influence of the surface charge of cysteine (CYS)-stabilized AgNPs on their toxicity towards human normal B (COLO-720L) and T (HUT-78) lymphocyte cell lines. CYS-AgNPs were synthesized via the chemical reduction. Transmission electron microcopy (TEM) imaging revealed that they exhibited a quasi-spherical shape with an average size of 18 ± 3 nm. CYS-AgNPs remained stable under mild acidic (pH 4.0) and alkaline (7.4 and 9.0) conditions, with an isoelectric point observed at pH 5.1. Following a 24 h treatment of lymphocytes with CYS-AgNPs, concentration-dependent alterations in cell morphology were observed. Positively charged CYS-AgNPs notably decreased lymphocyte viability. Furthermore, they exhibited grater genotoxicity and more pronounced disruption of biological membranes compared to negatively charged CYZ-AgNPs. Despite both types of AgNPs interacting similarly with fetal bovine serum (FBS) and showing comparable profiles of silver ion release, the biological assays consistently revealed that the positively charged CYS-AgNPs exerted stronger effects at all investigated cellular levels. Although both types of CYS-AgNPs have the same chemical structure in their stabilizing layers, the pH-induced alterations in their surface charge significantly affect their biological activity.

Effect of the interlayer distribution of ZnO decorated with Ag nanoparticles on the antimicrobial activity of multilayer poly(methyl methacrylate) films

AbstractIncorporating nanoparticles into polymer matrices for enhanced antimicrobial properties is particularly interesting. This study examines how the interlayer distribution of zinc oxide (ZnO) decorated with silver nanoparticles (AgNPs) within poly(methyl methacrylate) (PMMA) films impacts their antimicrobial activity. Various PMMA multilayer films were prepared, with the antimicrobial additive intentionally placed in the outer, core, bottom, or throughout all layers. Their efficacy was tested against gram‐negative (Escherichia coli) and gram‐positive (Staphylococcus aureus) bacteria. Results indicate that E. coli was the strain with the highest sensitivity to the system because it is a gram (−) bacterium, which could generate a lower resistance to AgNPs. On the other hand, S. aureus, being gram (+), presents a thicker lipid membrane, and peptidoglycan wall, which makes it difficult for AgNPs to enter. Films with uniform distribution throughout thickness exhibited the most sustained antimicrobial activity due to high antimicrobial concentration. This study demonstrated that the distribution of the AgNPs/ZnO system in different layers of a PMMA film influences its antimicrobial capacity. Finally, a mechanism for migrating silver ions released from the AgNPs/ZnO system in PMMA films is proposed, highlighting their interactions with bacterial cells and the subsequent antimicrobial effects.Highlights Interlayer distribution influences antimicrobial activity. Outer placement leads to rapid silver ion release. Core distribution controls antimicrobial kinetics. Uniform distribution ensures sustained activity.

Increased Cytotoxicity of Bimetallic Ultrasmall Silver-Platinum Nanoparticles (2 nm) on Cells and Bacteria in Comparison to Silver Nanoparticles of the Same Size.

Ultrasmall nanoparticles (diameter 2 nm) of silver, platinum, and bimetallic nanoparticles (molar ratio of Ag:Pt 0:100; 20:80; 50:50; 70:30; 100:0), stabilized by the thiolated ligand glutathione, were prepared and characterized by transmission electron microscopy, differential centrifugal sedimentation, X-ray photoelectron spectroscopy, small-angle X-ray scattering, X-ray powder diffraction, and NMR spectroscopy in aqueous dispersion. Gold nanoparticles of the same size were prepared as control. The particles were fluorescently labeled by conjugation of the dye AlexaFluor-647 via copper-catalyzed azide-alkyne cycloaddition after converting amine groups of glutathione into azide groups. All nanoparticles were well taken up by HeLa cells. The cytotoxicity was assessed with an MTT test on HeLa cells and minimal inhibitory concentration (MIC) tests on the bacteria Escherichia coli and Staphylococcus xylosus. Notably, bimetallic AgPt nanoparticles had a higher cytotoxicity against cells and bacteria than monometallic silver nanoparticles or a physical mixture of silver and platinum nanoparticles. However, the measured release of silver ions from monometallic and bimetallic silver nanoparticles in water was very low despite the ultrasmall size and the associated high specific surface area. This is probably due to the surface protection by a dense layer of thiolated ligand glutathione. Thus, the enhanced cytotoxicity of bimetallic AgPt nanoparticles is caused by the biological environment in cell culture media, together with a polarization of silver by platinum.

Preparation and Performance Study of a Hydrophobic Antimicrobial Nanoscale Aqueous Paint

This study involved the synthesis of core–shell nanostructured Ag@SiO2 materials, and based on these materials, a novel nanoscale water-based paint with excellent water resistance and antimicrobial properties was developed. The obtained samples were characterized using transmission electron microscopy (TEM), contact angle measurements, and antimicrobial testing. The experimental results indicate that in the nanoscale water-based paint, SiO2 nanoparticles effectively bond with acrylic ester (HBP). The high-strength SiO2 nanoparticles play a crucial role in improving the coating’s abrasion resistance. The nanoscale silver (Ag@SiO2) continuously releases silver ions, thereby inhibiting the formation of bacterial biofilms on the coating surface and preventing subsequent biofouling, thus enhancing the coating’s antimicrobial and anti-fouling capabilities. Based on these unique characteristics, this water-based paint holds promise for applications in architectural coatings and marine anti-fouling coatings.

Silver phosphate-modified carbonate apatite honeycomb scaffolds for anti-infective and pigmentation-free bone tissue engineering

Bone regeneration using synthetic materials has a high rate of surgical site infection, resulting in severe pain for patients and often requiring revision surgery. We propose Ag3PO4-based surface modification and structural control of scaffolds for preventing infections in bone regeneration. We demonstrated the differences in toxicity and antibacterial activity between in vitro and in vivo studies and determined the optimal silver content in terms of overall anti-infection effects, bone regeneration, toxicity, and pigmentation. A honeycomb structure comprising osteoconductive and resorbable carbonate apatite (CAp) was used as the base scaffold. CAp in the scaffold surface was partially replaced with different concentrations of Ag3PO4 via controlled dissolution-precipitation reactions in an AgNO3 solution. Both bone regeneration and infection prevention were achieved at 860–2300 ppm of silver. Despite the absence of Ag3PO4, honeycomb scaffolds were less susceptible to infection, even under conditions where infection occurs in clinically used three-dimensional porous scaffolds. Regardless of in vitro cytotoxicity at >5200 ppm of silver, increasing the silver content to 21,000 ppm did not adversely affect in vivo bone formation and scaffold resorption or cause acute systemic toxicity. Rather, bone formation was enhanced with 5200 ppm of silver. However, pigmentation was observed at that concentration. Hence, we concluded that the optimal silver concentration range is 860–2300 ppm for anti-infective and pigmentation-free bone regeneration. Bone regeneration was achieved via surface modification, resulting in the rapid release of silver ions immediately after implantation, followed by gradual release over several months. The scaffold structure may also aid in preventing bacterial growth within the scaffolds.

Long-Term Prevention of Biofilm Formation by Polycatechol-Based Supramolecular Assemblies with Low Molecular Weight Polymers on Surfaces.

Achievement of a stable surface coating with long-term resistance to biofilm formation remains a challenge. Catechol-based polymerization chemistry and surface deposition are used as tools for surface modification of diverse materials. However, the control of surface deposition of the coating, surface coverage, coating properties, and long-term protection against biofilm formation remain to be solved. We report a new approach based on supramolecular assembly to generate long-acting antibiofilm coating. Here, we utilized catechol chemistry in combination with low molecular weight amphiphilic polymers for the generation of such coatings. Screening studies with diverse low molecular weight (LMW) polymers and different catechols are utilized to identify lead compositions, which resulted in a thick coating with high surface coverage, smoothness, and antibiofilm activity. We have identified that small supramolecular assemblies (∼10 nm) formed from a combination of polydopamine and LMW poly(N-vinyl caprolactam) (PVCL) resulted in relatively thick coating (∼300 nm) with excellent surface coverage in comparison to other polymers and catechol combinations. The coating properties, such as thickness (10-300 nm) and surface hydrophilicity (with water contact angle: 20-60°), are readily controlled. The optimal coating composition showed excellent antibiofilm properties with long-term (>28 days) antibiofilm activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) strains. We further utilized the combination of optimal binary coating with silver to generate a coating with sustained release of silver ions, resulting in killing both adhered and planktonic bacteria and preventing long-term surface bacterial colonization. The new coating method utilizing LMW polymers opens a new avenue for the development of a novel class of thick, long-acting antibiofilm coatings.

Evaluation of the immunotoxicity potential of nanomaterials using THP-1 cells.

With the expansion of nanomaterials (NMs) usage, concerns about their toxicity are increasing, and the wide variety of NMs makes it difficult to assess their toxicity. Therefore, the development of a high-throughput, accurate, and certified method to evaluate the immunotoxicity of NMs is required. In this study, we assessed the immunotoxicity potential of various NMs, such as nanoparticles of silver, silica, and titanium dioxide, using the human Cell Line Activation Test (h-CLAT) at the cellular level. After exposure to silver nanoparticle dispersions, the expression levels of CD86 and CD54 increased, suggesting the activation of antigen-presenting cells (APCs) by silver nanoparticles. Quantification of silver ions eluted from silver nanoparticles and the activation of APCs by silver ions suggested that it was due to the release of silver ions. Silica nanoparticles also increased the expression of CD86 and/or CD54, and their activation ability correlated with the synthesis methods and hydrodynamic diameters. The ability of titanium dioxide to activate APCs differed depending on the crystal type and hydrodynamic diameter. These results suggest a potential method to evaluate the immunotoxicity potential of various NMs based on their ability to activate APCs using human monocytic THP-1 cells. This method will be valuable in assessing the immunotoxicity potential and elucidating the immunotoxic mechanisms of NMs.

The Influence of Different Sera on the Anti-Infective Properties of Silver Nitrate in Biopolymer Coatings.

The widespread prevalence of periprosthetic joint infections (PJIs) poses significant challenges in orthopedic surgeries, with pathogens such as Staphylococcus epidermidis being particularly problematic due to their capability to form biofilms on implants. This study investigates the efficacy of an innovative silver nitrate-embedded poly-L-lactide biopolymer coating designed to prevent such infections. The methods involved applying varying concentrations of silver nitrate to in vitro setups and recording the resultant bacterial growth inhibition across different serum environments, including human serum and various animal sera. Results highlighted a consistent and significant inhibition of S. epidermidis growth at all tested concentrations in each type of serum without adverse interactions with serum proteins, which commonly compromise antimicrobial efficacy. This study concludes that the silver nitrate-embedded biopolymer coating exhibits potent antibacterial properties and has potential for use in clinical settings to reduce the incidence of PJIs. Furthermore, the findings underscore the importance of considering serum interactions in the design and testing of antimicrobial implants to ensure their effectiveness in actual use scenarios. These promising results pave the way for further research to validate and refine this technology for clinical application, focusing on optimizing silver ion release and assessing biocompatibility in vivo.

In Vitro Efficacy of Silver Carbene Complexes, SCC1 and SCC22, Against Some Enteric Animal Pathogens

Silver carbene complexes (SCCs), a group of novel silver-based compounds capable of gradually releasing silver ions, have shown significant antimicrobial activity against a wide range of bacterial pathogens mainly isolated from human cases. The antimicrobial activity against animal isolated pathogens has yet been done. The in vitro efficacy of two SCCs with different carrier molecules (SCC1 with a methylated caffeine backbone and SCC22 with a dichloroimidazolium backbone) was investigated against three important animal and human pathogen species. SCC1 and SCC22 exhibited bacteriostatic and bactericidal effects against multidrug resistant Salmonella Typhimurium (poultry isolate), E. coli 843 and E. coli 1568 (swine isolates), and the poultry field isolates Salmonella Heidelberg, Salmonella Enteritidis, and Salmonella Montevideo with MICs and MBCs ranged from 16-21 µM (6-8 µg/mL) and 16-32 µM (6-12 µg/mL), respectively. Clostridium perfringens type A was sensitive to both SCC1 and SCC22 with the MICs being 11 (4 µg/mL) and 21 µM (8 µg/mL), respectively. These values were comparable to the MICs and MBCs for silver acetate. The MBCs against C. perfringens was >85 µM for SCCs and >192 µM for silver acetate (>32 µg/mL for all compounds). Ten hours incubation of C. perfringens with 40 µg/mL of all three products showed down regulation of virulence genes plc and netB, suggesting viable cells and silver can modulate the virulence. Treating the C. perfringens with higher concentration (100 µg/mL) of each SCC for 10 hours inhibited more bacteria compared to the untreated bacterial cells, however, no differences in the ultrastructure of lysed bacteria were seen and this concentration might not induce viable but non-culturable (VBNC) state as suggested by transmission electron microscopy findings. SCCs showed a broad antimicrobial activity against all bacterial species tested including multidrug resistant pathogens. Both SCCs demonstrated inhibitory effect against the Gram-positive anaerobic C. perfringens type A which could have a high accumulation capacity for silver ion. These data suggest that SCCs may represent a novel class of broad-spectrumantimicrobial agents, which may be used to reduce the burden of pathogenic bacteria in the gastrointestinal tract of poultry.