Silver Release Research Articles

Optimum coating layer thicknesses of a TRISO having an 800-μm UO2 kernel under normal operation conditions of a 10-MWth block-type HTGR

The study evaluates the optimal thicknesses of the coating layers of an 800-μm UO2 tri-structural isotropic coated fuel particle (TRISO) for a 10-MWth block-type micro modular high temperature gas-cooled reactor (HTGR) using a response surface methodology (RSM) and an HTGR fuel performance analysis code, COPA. The objective function to be minimized in the optimal design of a TRISO consists of the product of the packing fraction of TRISO particles in a compact, the fractional releases of major metallic fission products from a TRISO and the failure probability of the silicon carbide (SiC) layers. A constraint on the sum of the coating layer thicknesses was made using a maximum packing fraction. Two fuel performance analyses such as a failure fraction analysis and a fission product release analysis are applied to the optimal designs of a TRISO that the RSM produced. An 800-μm UO2 TRISO having buffer, inner high-density pyrocarbon (IPyC), SiC, outer high-density pyrocarbon (OPyC), each with a thickness of 110, 40, 57, 35 μm, or 120, 35, 60, 27 μm is suitable for the operation of a 10-MWth block-type micro modular HTGR within 7600 days when both the SiC and through-coatings failure fractions do not occur and the fractional release of silver, cesium, strontium and krypton are below 1 × 10−9. The packing fraction of the optimal TRISOs in a compact is 40%.

Speciation, controlling steps and pathways of silver release from the sludge generated from coagulation of wastewater spiked with silver nanoparticles

Sludge generated in wastewater treatment facilities is an integral part for the introduction of silver nanoparticles (AgNPs) to the terrestrial environment, which would cause some adverse ecosystem responses. The understanding of silver release process from the sludge is important to evaluate their risks. In this study, the amount and speciation of the released silver were investigated by taking the sludge generated by wastewater coagulation with AgNPs added (denoted as sludgeC-AgNPs) an example, and kinetic analysis and density functional theory (DFT) calculations were first used to explore the controlling steps and pathways about the silver release. The results showed that sludgeC-AgNPs could release the dissolved silver and the colloidal silver. Beside Cl−, Ca2+ in the leaching solution could enhance the silver release of sludgeC-AgNPs, especially for the colloidal silver. The released colloidal silver restricted in size from 40 nm to 100 nm with irregular shape. Although the oxidative dissolution of Ag0 was the origin of the silver release pathways from the sludgeC-AgNPs, the silver diffusion was the controlling step due to the spontaneous binding between silver and the hydrolysates of polyaluminium chloride in sludgeC-AgNPs. However, Ca2+ in the leaching solution could occupy the binding site of silver on sludgeC-AgNPs, which would increase the diffusion rate of silver over the oxidative rate of Ag0. With this condition, the controlling step of silver release from sludgeC-AgNPs turned to the oxidative dissolution of Ag0. Our findings are important to assess the fate of AgNPs in wastewater treatment as well as sludge applications.

Exploring hierarchical porous silica-supported Ag3PO4 as high-efficient and environmental-friendly photocatalytic disinfectant

Silver orthophosphate (Ag3PO4) is an attractive photocatalytic catalyst for disinfection and degradation, but its instability arising from silver release generates significant environmental issue. Aiming to develop a highly efficient and environmental-friendly catalyst, we synthesized Ag3PO4 nanoparticle incorporated hierarchical porous silica (Ag3PO4@h-SiO2) as a novel high-performance photocatalytic catalyst without observed silver release. Brain-like hierarchical porous SiO2 (h-SiO2) brings a scaffold support with high surface areas, and the h-SiO2 surface modified thiols are able to anchor in situ formed 10 nm Ag3PO4 to eliminate silver release. Systematic investigations revealed that because of its structural advantages, Ag3PO4@h-SiO2 show excellent disinfection and degradation ability under visible-light irradiation and stable characteristics without obviously observed silver leaching during photo-oxidation operation. In-depth scavenger study reveals Ag3PO4@h-SiO2 as an effective semiconducting photocatalyst stimulates the production of photo-generated reactive species, which dominate its distinguished disinfection performance via photo-oxidation.Graphical abstractAg3PO4 are anchored to thiol modified hierarchical porous SiO2 to produce a visible-light responsive photocatalyst of Ag3PO4@h-SiO2. The enhanced catalytic sites and surface areas promote pathogen disinfection, and the structure advantages minimize silver release to environment. Both H2O2 and holes being generated in photocatalysis dominate overall disinfection activity.

Ag- and Sr-enriched nanofibrous titanium phosphate phases as potential antimicrobial cement and coating for a biomedical alloy

Biomaterials and their surfaces regulate the biological response and ultimately the quality of healing at a possible site of implantation. The physical, chemical and topographical properties of implants' surfaces play a decisive role in the biological integration process for their immediate loading and long-term success. Since at this level of biological interaction nano-dimensionality is basically entailed, bio-functional nanostructured composites either as filling/cement or coating to metallic implants are required. This study shows the possibility of synthesizing two phases of nanostructured titanium phosphate (π and ρ polymorphs) and enriching them with silver nanoparticles and strontium. More importantly, Ag-Sr-enriched nanostructured π‑titanium phosphate is induced to grow on a commercially available titanium alloy (Ti-6Al-4V), widely used in orthopedic and dental implants, under highly controlled conditions. Structural and microscopic studies, using XRD, HRTEM and SEM altogether confirm the resultant phases and their enrichment with strontium and silver nanoparticles with an average particle size around 6 nm. Using confocal laser scanning microscopy, the surface roughness was measured and is found to lay at the interface between the nanosized and microsized topologies. Ion release assessments showed that the presence of strontium controlled the release rate of silver ions and this could be beneficial in terms of decreasing the accompanied cytotoxicity that is usually encountered at high concentrations of silver release. Antimicrobial and cell proliferation assays have proved that enriching titanium phosphate with strontium and silver nanoparticles has improved their antimicrobial properties, while the cytotoxicity could be controlled.

Formulation of inherently antimicrobial magnesium oxychloride cement and the effect of supplementation with silver phosphate

The growing threat of bacterial resistance to antibiotics is driving an increasing need for new antimicrobial strategies. This work demonstrates the potential of magnesium oxychloride cements (MOC) to be used as inorganic antimicrobial biomaterials for bone augmentation. An injectable formulation was identified at a powder to liquid ratio of 1.4 g mL−1, with an initial setting time below 30 mins and compressive strength of 35 ± 9 MPa. Supplementation with Ag3PO4 to enhance the antimicrobial efficacy of MOC was explored, and shown via real time X-ray diffraction to retard the formation of hydrated oxychloride phases by up to 30%. The antimicrobial efficacy of MOC was demonstrated in vitro against Staphylococcus aureus and Pseudomonas aeruginosa, forming zones of inhibition and significantly reducing viability in broth culture. Enhanced efficacy was seen for silver doped formulations, with complete eradication of detectable viable colonies within 3 h, whilst retaining the cytocompatibility of MOC. Investigating the antimicrobial mode of action revealed that Mg and Ag release and elevated pH contributed to MOC efficacy. Sustained silver release was demonstrated over 14 days, suggesting the Ag3PO4 modified formulation offers two mechanisms of infection treatment, combining the inherent antimicrobial properties of MOC with controlled release of inorganic antimicrobials.

Two‐step ion‐exchanged soda lime silicate glass: Effect of surface compression on silver ion release

AbstractAlthough glass plays an important role in medical facilities such as countertops or interfaces of medical equipment, where chemical and mechanical durability is of great concern, less attention has been paid to developing durable anti‐microbial surfaces. In the present work, silver‐containing surfaces were produced by ion exchange in soda‐lime silicate float glass, and the effects of residual surface compression produced by ion‐exchange on the release of silver ions were investigated. Silver‐doped surfaces were prepared by a sequential two‐stage ion‐exchange process in pure potassium nitrate, at 450°C for 4‐24 hours, and subsequently in KNO3+ 1 wt% AgNO3, at 400°C for 10‐30 minutes. Silver ions were found to penetrate 3‐5 µm into the glass surface, causing only a limited decrease in surface compression induced by potassium ions. The silver‐rich layer provides the required Ag+ leaching essential for anti‐microbial applications, as confirmed by Ag+ ion leaching tests. The silver release can be altered by surface compression.

Antibacterial Electrospun Polycaprolactone Membranes Coated with Polysaccharides and Silver Nanoparticles for Guided Bone and Tissue Regeneration.

Electrospun polycaprolactone (PCL) membranes have been widely explored in the literature as a solution for several applications in tissue engineering and regenerative medicine. PCL hydrophobicity and its lack of bioactivity drastically limit its use in the medical field. To overcome these drawbacks, many promising strategies have been developed and proposed in the literature. In order to increase the bioactivity of electrospun PCL membranes designed for guided bone and tissue regeneration purposes, in the present work, the membranes were functionalized with a coating of bioactive lactose-modified chitosan (CTL). Since CTL can be used for the synthesis and stabilization of silver nanoparticles, a coating of this compound was employed here to provide antibacterial properties to the membranes. Scanning electron microscopy imaging revealed that the electrospinning process adopted here allowed us to obtain membranes with homogeneous fibers and without defects. Also, PCL membranes retained their mechanical properties after several weeks of aging in simulated body fluid, representing a valid support for cell growth and tissue development. CTL adsorption on membranes was investigated by fluorescence microscopy using fluorescein-labeled CTL, resulting in a homogeneous and slow release over time. Inductively coupled plasma-mass spectrometry was used to analyze the release of silver, which was shown to be stably bonded to the CTL coating and to be slowly released over time. The CTL coating improved MG63 osteoblast adhesion and proliferation on membranes. On the other hand, the presence of silver nanoparticles discouraged biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus without being cytotoxic. Overall, the stability and the biological and antibacterial properties make these membranes a valid and versatile material for applications in guided tissue regeneration and in other biomedical fields like wound healing.

Comparative Analysis of Electrospun Uniaxial and Coaxial Nanofibers Properties

Coaxial electrospinning, which is a modified electrospinning technique involving an arrangement of multiple solution feed systems, enable the production of multilayered nanofibers. In this study, multilayered nanofibers of polyamide 6 (core) / polycaprolactone (shell) containing silver nanoparticles in the core were produced by coaxial electrospinning method. UV-Visible spectra showed that the size of nanoparticles were about 10 nm and the content of nanoparticles were observed to be proportional to the precursor content added to the solvent. The obtained multilayered nanofibers were characterized in terms of morphology, chemical structure, and silver release properties. The multilayered nanofiber structure was confirmed by the selective dissolution and removal of shell layer. The increase in the PCL content of the multilayered nanofibers with the increase in the flow rate of the shell solution was confirmed by FTIR. The silver release profiles of the nanofibers were observed to be dependent on the nanofiber configuration, and silver content. Shell thickness was also an important parameter affecting the silver release properties for multilayered nanofibers.

Effects of M2O3 (M = Bi, Al) on silver vanadate glass for radioactive iodine immobilization

This study investigated the effects of Bi2O3 and Al2O3 on silver vanadate glasses for iodine immobilization. An iodine immobilization matrix was developed and examined with M2O3 (M = Bi, Al) as additives for a AgI-Ag2O-V2O5 glass system. Immobilization was confirmed at 800 °C after 1 h of melting without significant loss of the elements that constituted the glass, excluding aluminum. The loading of iodine in the matrix was approximately 30–36% by weight, excluding oxygen. Normalized releases of all elements obtained were below the order of 10−1 g/m2, which satisfies the USA regulation (2 g/m2). The structural factors that influenced the chemical durability of the glass and suppressed iodine release were discussed. The addition of M2O3 (M = Bi, Al) suppressed iodine release by the formation of a VO4 tetrahedron from the V2O5 glass matrix. The release of silver was not as suppressed as that of iodine.

Monitoring the Release of Silver from a Supramolecular Fullerene C60-AgNO3 Nanomaterial

Abstract Release of silver from the supramolecular fullerene-silver(I) nitrate complex C60(AgNO3)5 was investigated. Silver(I) nitrate release from the complex on treatment with solvent was monitored using the small molecule organo-supergelator 1-phenyl-3-(quinolin-5-yl)urea, which interacts selectively with AgNO3 yielding a stable gel whose extent (i.e. volume fraction of solvent gelated) and persistence indicate that Ag+ cations are continuously released from the complex when immersed in 2-propanol over extended periods of time. The effect of AgNO3 release on the morphology of the C60(AgNO3)5 complex crystals was evaluated using scanning electron microscopy showing that AgNO3 is concurrently deposited as silver nanoparticles at the crystal-solution interface onto an insoluble C60 crystalline framework. Silver release was also monitored potentiometrically revealing emergence of Ag nanoparticles. Initial intense release of Ag+ (in the form of AgNO3) is followed by reductive fixing of silver in nanoparticulate form for longer term bactericidal activity. The latter was established by observing viability of bacterial colonies in aqueous medium where their growth was essentially arrested when C60(AgNO3)5 crystals were present in the medium in contrast to the case for pristine C60 where colony growth proceeded unhindered. Cell proliferation studies using HeLa cell line revealed that C60(AgNO3)5 crystals also exhibit antiproliferative properties in aqueous media.

The role of silver coating for arthroplasty components.

Periprosthetic joint infection (PJI) is one of the most dreaded complications after arthroplasty surgery; thus numerous approaches have been undertaken to equip metal surfaces with antibacterial properties. Due to its antimicrobial effects, silver is a promising coating for metallic surfaces, and several types of silver-coated arthroplasty implants are in clinical use today. However, silver can also exert toxic effects on eukaryotic cells both in the immediate vicinity of the coated implants and systemically. In most clinically-used implants, silver coatings are applied on bulk components that are not in direct contact with bone, such as in partial or total long bone arthroplasties used in tumour or complex revision surgery. These implants differ considerably in the coating method, total silver content, and silver release rates. Safety issues, such as the occurrence of argyria, have been a cause for concern, and the efficacy of silver coatings in terms of preventing PJI is also controversial. The application of silver coatings is uncommon on parts of implants intended for cementless fixation in host bone, but this option might be highly desirable since the modification of implant surfaces in order to improve osteoconductivity can also increase bacterial adhesion. Therefore, an optimal silver content that inhibits bacterial colonization while maintaining osteoconductivity is crucial if silver were to be applied as a coating on parts intended for bone contact. This review summarizes the different methods used to apply silver coatings to arthroplasty components, with a focus on the amount and duration of silver release from the different coatings; the available experience with silver-coated implants that are in clinical use today; and future strategies to balance the effects of silver on bacteria and eukaryotic cells, and to develop silver-coated titanium components suitable for bone ingrowth. Cite this article: Bone Joint J2021;103-B(3):423-429.

Effect of ionising irradiation on silver release from polyolefin/silver nanocomposite films into food simulants

ABSTRACT Two types of nanocomposite films, polyethylene/silver (PE/Ag) and polypropylene/silver (PP/Ag), were prepared and characterised. Assessment of silver released under the effect of ionising irradiation was performed on the nanocomposite films. The release experiment was carried out by immersing the nanocomposite films in water, 3% acetic acid or 95% ethanol as food simulants and measuring the Ag release from nanocomposite films treated with and without gamma or electron beam irradiation at a dose of 10 kGy. In general, irradiation treatment increased the Ag release regardless of the type of polymer and food simulant. One reason could be radiation-induced metal oxidation at the surface which in turn promoted ion release into food simulants. The oxidising radicals produced by radiation in solution could be another factor speeding up metal oxidation and subsequent ion release. When comparisons were made between the two types of irradiation, greater Ag release into water and 3% acetic acid was observed after electron beam irradiation, while gamma irradiation was likely to induce greater Ag release into 95% ethanol. Such phenomena reveal the influence of different types of radiation on the solutions which in turn affect the Ag release.

Cysteamine: A key to trigger aggregation-induced NIR-II photothermal effect and silver release booming of gold-silver nanocages for synergetic treatment of multidrug-resistant bacteria infection

Gold silver nanocages (GSNCs) have been applied as an excellent nano-cargo for drug delivery and near infrared (NIR) photothermal therapy due to their tunable optical properties and biocompatibility. However, a dilemma is that GSNCs with NIR adsorption normally have a highly-hollow silver core and thick gold coating, which largely mitigates the antibacterial activity because of the limited use of contained silver species. Here we have proposed an alternative strategy on basis of the aggregation induced photothermal (AIP) effect by the combination of high silver-loading GSNCs and thiolates. Interestingly, a typical thiolate, cysteamine, was found to rapidly induce the release of ultrasmall silver alloy species from GSNCs, with at least 4 fold amount compared with that by other thiolates. The booming silver release from GSNCs and NIR photothermal effect synergistically allow the removal of the biofilm secreted by multidrug resistant (MDR) bacteria in vitro and the eradication of MDR S. aureus in infection wound of mice. This strategy may provide a promising method for effective treatment of intractable MDR bacterial infection.

Cytotoxic and genotoxic effects in human gingival fibroblast and ions release of endodontic sealers incorporated with nanostructured silver vanadate.

The cytotoxic and genotoxic effects of commercial endodontic sealers (AH Plus, Sealer 26 and Endomethasone N) incorporated with nanostructured silver vanadate decorated with silver nanoparticles (AgVO3 - at concentrations 2.5, 5, and 10%) on human gingival fibroblast (HGF), and the silver (Ag+ ) and vanadium (V4+ /V5+ ) ions release were evaluated. Cytotoxicity, cell death, and genotoxicity tests were carried out with extract samples of 24-hr and 7-days. The release of Ag+ and V4+ /V5+ was evaluated. Cytotoxicity in HGF was caused by AH Plus (AP) with 5 and 10% of AgVO3 (83.84 and 67.49% cell viability, respectively) with 24-hr extract (p < 0.05), as well as all concentrations of AP with 7-days extract (p < 0.05 -AP 0%=73.17%; AP 2.5%=75.07%; AP 5%=70.62%; AP 10%=68.46% cell viability). The commercial sealers Sealer 26 (S26) and Endomethasone N (EN) were cytotoxic (p < 0.05 - S26 0%=34.81%; EN 0%=20.99% cell viability with 7-days extract). AP 10% with 7-days extract induced 32% apoptotic cells in HGF (p < 0.05). Genotoxic effect was not observed. The AP groups released more Ag+ , while S26 and EN released more V4+ /V5+ in 24 hr. The Ag+ can be cytotoxic. In conclusion, the cytotoxicity caused to HGF can be attributed by the commercial sealers and enhanced by incorporation of AgVO3 , was not observed genotoxic effect, and apoptosis was induced only by AH Plus 10% 7-days extract. Ag+ can influence cell viability.

Incorporation of Hybrid Nanomaterial in Dental Porcelains: Antimicrobial, Chemical, and Mechanical Properties.

Biofilm formation on biomaterials is a challenge in the health area. Antimicrobial substances based on nanomaterials have been proposed to solve this problem. The aim was to incorporate nanostructured silver vanadate decorated with silver nanoparticles (β-AgVO3) into dental porcelains (IPS Inline and Ex-3 Noritake), at concentrations of 2.5% and 5%, and evaluate the surface characteristics (by SEM/EDS), antimicrobial activity (against Streptococcus mutans, Streptococcus sobrinus, Aggregatibacter actinomycetemcomitans, and Pseudomonas aeruginosa), silver (Ag+) and vanadium (V4+/V5+) ions release, and mechanical properties (microhardness, roughness, and fracture toughness). The β-AgVO3 incorporation did not alter the porcelain’s components, reduced the S. mutans, S. sobrinus and A. actinomycetemcomitans viability, increased the fracture toughness of IPS Inline, the roughness for all groups, and did not affect the microhardness of the 5% group. Among all groups, IPS Inline 5% released more Ag+, and Ex-3 Noritake 2.5% released more V4+/V5+. It was concluded that the incorporation of β-AgVO3 into dental porcelains promoted antimicrobial activity against S. mutans, S. sobrinus, and A. actinomycetemcomitans (preventing biofilm formation), caused a higher release of vanadium than silver ions, and an adequate mechanical behavior was observed. However, the incorporation of β-AgVO3 did not reduce P. aeruginosa viability and increased the surface roughness of dental porcelains.

Antibacterial Synergism of Electrospun Nanofiber Mats Functioned with Silver Nanoparticles and Pulsed Electromagnetic Waves.

The over-reliance on antibiotics and their enormous misuse has led to warnings of a future without effective medicines and so, the need for alternatives to antibiotics has become a must. Non-traditional antibacterial treatment was performed by using an aray of nanocomposites synergised with exposure to electromagnetic waves. In this manuscript, electrospun poly(vinyl alcohol) (PVA) nanofiber mats embedded with silver nanoparticles (Ag NPs) were synthesized. The nanocomposites were characterized by Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), Current-Voltage (I-V) curves, and Thermogravimetric analysis (TGA) along with analysis of antibacterial impact against E. coli and S. aureus bacteria, studied by bacterial growing analysis, growth kinetics, and cellular cytotoxicity. The results indicated a spherical grain shape of silver of average size 20 nm and nanofibers’ mean diameter of less than 100 nm. The nanocomposite mats showed good exposure to bacteria and the ability to sustain release of silver for a relatively long time. Moreover, the applied electromagnetic waves (EMWs) were shown to be a synergistic co-factor in killing bacteria even at low concentrations of Ag NPs. This caused pronounced alterations of the bacterial preserved packing of the cell membrane. Thereby, the treatment with nanocomposite mats under EM wave exposure elucidated maximum inhibition for both bacterial strains. It was concluded that the functioning of nanofiber with silver nanoparticles and exposure to electromagnetic waves improved the antibacterial impact compared to each one alone.

The Development of Solvent Cast Films or Electrospun Nanofiber Membranes Made from Blended Poly Vinyl Alcohol Materials with Different Degrees of Hydrolyzation for Optimal Hydrogel Dissolution and Sustained Release of Anti-Infective Silver Salts.

Introduction: We previously described the manufacture and characterization of hydrogel forming, thin film, anti-infective wound dressings made from Poly Vinyl Alcohol (PVA) and silver nanoparticles, crosslinked by heat. However, these films were designed to be inexpensive for simple manufacture locally in Africa. In this new study, we have further developed PVA dressings by manufacturing films or electrospun membranes, made from blends of PVA with different degrees of hydrolyzation, that contain silver salts and degrade in a controlled manner to release silver in a sustained manner over 12 days. Methods: Films were solvent cast as films or electrospun into nanofibre membranes using blends of 99 and 88% hydrolyzed PVA, containing 1% w/w silver sulphadiazine, carbonate, sulphate, or acetate salts. Dissolution was measured as weight loss in water and silver release was measured using inductively coupled plasma (ICP) analysis. Results: Cast films generally stayed intact at PVA 99: PVA 88% ratios greater than 40:60 whereas electrospun membranes needed ratios greater than 10:90. Films (40:60 blend ratio) and membranes (10:90) all released silver salts in a sustained fashion but incompletely and to different extents. Electrospun membranes gave more linear release patterns in the 2–12 day period and all salts released well. Conclusion: Blended PVA cast films offer improved control over hydrogel dissolution and silver release without the need for high temperature crosslinking. Blended PVA electrospun membranes further improve membrane dissolution control and silver release profiles. These blended PVA films and membranes offer improved inexpensive systems for the manufacture of long lasting anti-infective hydrogel wound dressings.

Release of gold (Au), silver (Ag) and cerium dioxide (CeO2) nanoparticles from sewage sludge incineration ash.

Engineered nanoparticles (NPs) that are released into wastewater are retained by wastewater treatment plants (WWTPs) and accumulate in sewage sludge. Increasing shares of sludge are incinerated and landfilled, especially in industrialized countries. It is debated whether certain types of NPs can outlive the incineration process and subsequently be released from sewage sludge ash (SSA) landfills. To investigate the release of different types of NPs from SSA, we spiked gold (Au), silver (Ag) and cerium dioxide (CeO2) NPs to a pilot WWTP increasing the Au, Ag and Ce concentrations to 30, 43 and 389 mg kg−1 (dry matter basis) in the digested sludge. The spiked sludge was incinerated in a pilot fluidized bed reactor resulting in SSA with Au, Ag and Ce concentrations of 61, 103 and 854 mg kg−1. In addition, two sludge samples from a full-scale WWTP with Au concentrations of 5 and 16 mg kg−1 were incinerated, resulting in SSA with 9 mg kg−1 and 30 mg kg−1 Au. The spiked Au-NPs remain largely unaltered during the wastewater treatment and incineration process, whereas Ag-NPs and CeO2-NPs undergo transformation. During simulated landfill leaching in columns flushed with 400 to 500 pore volumes of artificial rainwater, Ag and Ce were retained in the ash, whereas about 17% of the spiked Au was released, mainly in particulate form. Lower fractions of mostly particulate Au were released from the ashes (3 and 9%) of unspiked SSA. In conclusion, unaltered Au-NPs significantly leach from landfilled SSA, whereas the incorporation of Ag-NPs and CeO2-NPs as transformed species into the SSA matrix limits the leaching of (nano)particulate and dissolved Ag and Ce compounds.

Nanostructured Carbon Fiber Modified by Silver Nanoparticles for the Medical Application

In this work, the feasibility of synthesizing new composite system for the medical application using an activated carbon fiber nanostructured materials with silver nanoparticles through immobilization by adsorption from solutions (ACFNM/AgNP) has been studied. The stability of the obtained composite system in physiological solutions as a modern sorption application form has been examined. Optimal modes of carbonized fabric activation are proposed for synthesis of nanostructured carbon fiber with high sorption capacity. The size distribution of silver nanoparticles after the ultrasonic treatment of the original silver solution in glycerol was proved to significantly decrease in the size of the agglomerates formed in the solution. It has been shown that after ultrasonic treatment, the silver nanoparticles were actively adsorbed by the porous structure of the carbon matrix. Treatment of carbon fiber with silver nanoparticles showed their uniform adsorption on the surface of the carbon matrix to form silver agglomerates with sizes of ~90–120 nm and 250– 300 nm. When studying the physicochemical stability of the obtained composite systems in biological solutions it was revealed that the intensity of silver release from the surface of the ACFNM/AgNP composite depends on the volumetric capacity of the carbon matrix, the initial concentration of silver in the solution, and the chemical composition of biological media. At that, the amount of silver in the water filtrate was established to be greater than in physiological solutions after the interaction. It was shown that the initial silver concentration of 25 mg/L in a suspension of glycerol is most optimal for creating of stable ACFNM/AgNP composite systems. Besides, the slower release of silver from the surface of carbon matrices into physiological solutions of different salt composition ensures a prolonged effect of silver in modern sorption application forms for medical purposes. The ACFNM/AgNP composite system with a capacity of carbon matrix of 1.0 cm3/g and an initial concentration of silver in a solution of 25 mg/L was recommended for the future development of modern application materials.

Bioactive glass doped with noble metal nanoparticles for bone regeneration: in vitro kinetics and proliferative impact on human bone cell line.

This work investigates the bioactivity of novel silver-doped (BG-Ag) and gold-doped (BG-Au) quaternary 46S6 bioactive glasses synthesized via a semi-solid-state technique. A pseudo-second-order kinetic model successfully predicted the in vitro uptake kinetic profiles of the initial ion-exchange release of Ca in simulated body fluid, the subsequent Si release, and finally, the adsorption of Ca and P onto the bioactive glasses. Doping with silver nanoparticles enhanced the rate of P uptake by up to approximately 90%; whereas doping with gold nanoparticles improved Ca and P uptake rates by up to about 7 and 2 times, respectively; as well as Ca uptake capacity by up to about 19%. The results revealed that the combined effect of Ca and Si release, and possibly the release of silver and gold ions into solution, influenced apatite formation due to their effect on Ca and P uptake rate and capacity. In general, gold-doped bioactive glasses are favoured for enhancing Ca and P uptake rates in addition to Ca uptake capacity. However, silver-doped bioactive glasses being less expensive can be utilized for applications targeting rapid healing. In vitro studies showed that BG, BG-Ag and BG-Au had no cytotoxic effects on osteosarcoma MG-63 cells, while they exhibited a remarkable cell proliferation even at low concentration. The prepared bioactive glass doped with noble metal nanoparticles could be potentially used in bone regeneration applications.