Antibacterial and Antiviral Activities of Silver Nanocluster/Silica Composite Coatings Deposited onto Air Filters.

The indoor air quality should be better controlled and improved to avoid numerous health issues. Even if different devices are developed for air filtration, the proliferation of microorganisms under certain conditions must be controlled. For this purpose, a silver nanocluster/silica composite coating was deposited via a cosputtering technique onto fiber glass and polymeric based substrates. The aim of this work is focused on the evaluation of the antibacterial and antiviral effects of the developed coating. The preliminary results of the compositional and morphological tests showed an evenly distributed coating on filters surfaces. Several antibacterial tests were performed, confirming strong effect both in qualitative and quantitative methods, against S. epidermidis and E. coli. To understand if the coating can stop the proliferation of bacteria colonies spread on it, simulation of everyday usage of filters was performed, nebulizing bacteria solution with high colonies concentration and evaluating the inhibition of bacteria growth. Additionally, a deep understanding of the virucidal action and mechanism of Ag nanoclusters of the coating was performed. The effect of the coating both in aqueous medium and in dry methods was evaluated, in comparison with analysis on ions release. The virucidal performances are assessed against the human coronavirus OC43 strain (HCoV-OC43).

Silver Nanoparticles: Review of Antiviral Properties, Mechanism of Action and Applications.

New antiviral drugs and new preventive antiviral strategies are a target of intense scientific interest. Thanks to their peculiar properties, nanomaterials play an important role in this field, and, in particular, among metallic materials, silver nanoparticles were demonstrated to be effective against a wide range of viruses, in addition to having a strong antibacterial effect. Although the mechanism of antiviral action is not completely clarified, silver nanoparticles can directly act on viruses, and on their first steps of interaction with the host cell, depending on several factors, such as size, shape, functionalization and concentration. This review provides an overview of the antiviral properties of silver nanoparticles, along with their demonstrated mechanisms of action and factors mainly influencing their properties. In addition, the fields of potential application are analyzed, demonstrating the versatility of silver nanoparticles, which can be involved in several devices and applications, including biomedical applications, considering both human and animal health, environmental applications, such as air filtration and water treatment, and for food and textile industry purposes. For each application, the study level of the device is indicated, if it is either a laboratory study or a commercial product.

Life cycle assessment for the production of MSWI fly-ash based porous glass-ceramics: Scenarios based on the contribution of silica sources, methane aided, and energy recoveries.

Municipal solid waste (MSW) production in the world has increased by 60 % in recent years. Incineration of MSW reduces their volume in conjunction with energy recovery. Incineration produces two residues, namely bottom ash (BA) and fly ash (FA), with high concentration of heavy metals and organic pollutants, especially for FA, making them an environmental concern. Vitrification is a costly, highly safe high temperature treatment, ensuring encapsulation of heavy metals. FA vitrification requires a source of silica to be able to get vitrified. In this study, we have proposed valorizing treated (vitrified) FA through the production of porous glass-ceramics, subsequently to MSWI. The entire process, from incineration to glass-ceramics production, was evaluated for several scenarios by Life Cycle Assessment (LCA) using Sima Pro 9.0. Three main scenarios were analysed; each one considering a different silica source: bottom ash (BA), glass cullet (G) and silica sand (S), and for each scenario, three thermal recovery subscenarios were assumed: no thermal recovery used to heat FA prior to vitrification (N), heating FA prior to vitrification using incineration gases thermal recovery (T) and methane-combustion-aided thermal recovery, which exploits methane combustion to further increase the gases temperature (M). Results proved that vitrification was a technically feasible and environmentally-energetically sustainable technology. The result indicates that the most eco-sustainable scenario was using bottom ashes as a silica source together with methane-combustion-aided recovery: 0.467 kgCO2,eq, 5.83 × 10-8 carcinogenic-CTUh and 9.26 MJ required per kg of glass-ceramics produced.

Development of a Membrane Module Prototype for Oxygen Separation in Industrial Applications.

The integration of oxygen transport membranes in industrial processes can lead to energy and economic advantages, but proof of concept membrane modules are highly necessary to demonstrate the feasibility of this technology. In this work, we describe the development of a lab-scale module through a comprehensive study that takes into consideration all the relevant technological aspects to achieve a prototype ready to be operated in industrial environment. We employed scalable techniques to manufacture planar La0.6Sr0.4Co0.2Fe0.8O3-δ membrane components suitable for the application in both 3- and 4-end mode, designed with a geometry that guarantees a failure probability under real operating conditions as low as 2.2 × 10-6. The asymmetric membranes that act as separation layers showed a permeation of approx. 3 NmL/min/cm2 at 900 °C in air/He gradient, with a remarkable stability up to 720 h, and we used permeation results to develop a CFD model that describes the influence of the working conditions on the module performance. The housing of the membrane component is an Inconel 625 case joined to the membrane component by means of a custom-developed glass-ceramic sealant that exhibited a remarkable thermo-chemical compatibility both with metal and ceramic, despite the appearance of chemical strain in LSCF at high temperature. The multi-disciplinary approach followed in this work is suitable to be adapted to other module concepts based on membrane components with different dimensions, layouts or materials.

Modelling, additive layer manufacturing and testing of interlocking structures for joined components.

In this study, authors explore the application of modelling and additive layer manufacturing (ALM) for creating and testing materials with interlocking structures aimed to reduce the stress concentration along the edges of a typical lap joint. The effectiveness of this approach is discussed by means of modelling and experimental validation of joints with interlocking structures obtained by ALM. Considering the achieved results, ALM of interlocking structures constitutes an interesting alternative or complement to traditional joining processes, as it may help to minimize stress mismatches in the joining region. It may also prevent the use of adhesive or joining post processes, because the joint is created together with the joined components.

High-Performance SiC-Based Solar Receivers for CSP: Component Manufacturing and Joining.

Concentrated solar power (CSP) is an important option as a competitive, secure, and sustainable energy system. At the moment, cost-effective solutions are required for a wider-scale deployment of the CSP technology: in particular, the industrial exploitation of CSP has been so far hindered by limitations in the materials used for the central receiver-a key component in the system. In this context, the H2020 NEXTOWER project is focused on next-generation CSP technologies, particularly on advanced materials for high temperatures (e.g., >900 °C) and extreme applications environments (e.g., corrosive). The research activity described in this paper is focused on two industrial solutions for new SiC ceramic receivers for high thermal gradient continued operations: porous SiC and silicon-infiltrated silicon carbide ceramics (SiSiC). The new receivers should be mechanically tough and highly thermally conductive. This paper presents the activity related to the manufacturing of these components, their joining, and characterization.

Brazing of Mo to Glidcop Dispersion Strengthened Copper for Accelerating Structures.

Alumina dispersion-strengthened copper, Glidcop, is used widely in high-heat-load ultra-high-vacuum components for synchrotron light sources (absorbers), accelerator components (beam intercepting devices), and in nuclear power plants. Glidcop has similar thermal and electrical properties to oxygen free electrical (OFE) copper, but has superior mechanical properties, thus making it a feasible structural material; its yield and ultimate tensile strength are equivalent to those of mild-carbon steel. The purpose of this work has been to develop a brazing technique to join Glidcop to Mo, using a commercial Cu-based alloy. The effects of the excessive diffusion of the braze along the grain boundaries on the interfacial chemistry and joint microstructure, as well as on the mechanical performance of the brazed joints, has been investigated. In order to prevent the diffusion of the braze into the Glidcop alloy, a copper barrier layer has been deposited on Glidcop by means of RF-sputtering.

Antibacterial and Bioactive Coatings Based on Radio Frequency Co-Sputtering of Silver Nanocluster-Silica Coatings on PEEK/Bioactive Glass Layers Obtained by Electrophoretic Deposition.

Bioactive and antibacterial coatings on stainless steel substrates were developed and characterized in this study. Silver nanocluster-silica composite coatings of 60-150 nm thickness were deposited using radio frequency (RF) co-sputtering on PEEK/bioactive glass (BG) layers (of 80-90 µm thickness) which had been electrophoretically deposited onto stainless steel. Two sputtering conditions were used by varying the deposition time (15 and 40 min); the resulting microstructure, composition, adhesion strength, in vitro bioactivity, and antibacterial activity were investigated. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDX) confirmed the presence of silver nanoclusters, which were homogeneously embedded in the silica matrix. The isoelectric point of the coatings and their charge at physiological pH were determined by zeta potential measurements. The presence of BG particles in the PEEK/BG layer allows the coatings to form apatite-like crystals upon immersion in simulated body fluid (SBF). Moreover, silver nanoclusters embedded in the silica matrix as a top layer provided an antibacterial effect against Escherichia coli and Staphylococcus carnosus.

Salmonella serovar-specific interaction with jejunal epithelial cells.

Gut is often a receptacle for many different pathogens in feed and/or the environment, such as Salmonella spp. The current knowledge about pathogenicity of Salmonella is restricted to few serotypes, whereas other important ones like S. Coeln, S. Thompson, S. Veneziana, have not been investigated yet in human and animal models. Therefore, the aim of our work was to verify the ability of widespread environmental Salmonella strains to penetrate and modulate innate immunity in pig intestinal IPEC-J2 cells. Our results outline the different ability of Salmonella strains to modulate innate immunity; the expression of the IFN-ß gene was increased by S. Typhimurium, S. Ablogame and S. Diarizonae 2, that also caused an inflammatory response in terms of Interleukin (IL)-1ß and/or IL-8 gene espression. In particular, IL-8 gene expression and protein release were significantly modulated by 5 Salmonella strains out of 7. Interestingly, S. Typhimurium, S. Coeln and S. Thompson strains, characterized by a peculiar ability to penetrate into IPEC-J2 cells, up-regulated both IL-8 and TNF-α gene expression. Accordingly, blocking IL-8 was shown to decrease the penetration of S. Typhimurium. On the contrary, S. Diarizonae strain 1, showing lesser invasion of IPEC-J2 cells, down-regulated the p38-MAPK pathway, and it did not induce an inflammatory response. Our results confirm that IPEC-J2 cells are a useful model to evaluate host-gut pathogen interaction and indicate IL-8 and TNF-α as possible predictive markers of invasiveness of Salmonella strains in enterocytes.

Biocompatibility versus peritoneal mesothelial cells of polypropylene prostheses for hernia repair, coated with a thin silica/silver layer.

Hernias are generally repaired using synthetic prostheses. Infection may already be present or develop during implantation. Based on the increasing resistance to antibiotics, and the well-known antimicrobial properties of silver (Ag), the possibility of coating hernia prostheses with a nanostructured layer containing Ag was explored. Prostheses (Clear Mesh Composite [CMC]) made up of two polypropylene layers (macroporous light mesh and thin transparent film) were tested with human mesothelial cells from omentum biopsies. Mesotheliocytes modulate abdominal wall healing producing cytokines, growth factors, and adhesion molecules. Evaluating the growth of these cells on CMC or film alone showed that cell numbers on CMC increased over time, and were higher than those on film alone. Vimentin immunostaining confirmed the cells to be mesotheliocytes. Subsequently, the biocompatibility of mesh layer, coated or not with a thin layer of Ag/SiO2 -nanoclusters, was analyzed, showing no difference in absence or presence of Ag/SiO2 . Differently, TGF-ß2 production, involved in tissue repair and fibrosis, increased in the presence of Ag/SiO2 . Moreover, Ag/SiO2 -coated mesh showed antibacterial properties. In conclusion, the mesh layer coated with Ag/SiO2 afforded cell growth, and showed antibacterial activity. Coating only the mesh layer did not decrease film transparency, and did not favor the formation of adhesions on the visceral side. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1586-1593, 2017.

Novel antibacterial ocular prostheses: Proof of concept and physico-chemical characterization.

Discouraging bacterial colonization of ocular biomaterials and implants is a significant challenge in ophthalmology as infections often lead to the need for secondary surgery, with associated risks and additional stress to patients. In this work we demonstrate for the first time the feasibility of an innovative antibacterial ocular prosthesis produced by depositing a silver nanocluster/silica composite layer on the poly(methyl methacrylate) implant surface via radio-frequency sputtering. Tape test performed according to relevant ASTM standard provided a preliminary evidence of the mechanical stability and good adhesion of the coating to the substrate (absence of macroscopic damage after tape removal). Coating integrity was maintained after prolonged soaking in aqueous medium (1 month). The antibacterial effect of the coating, associated to silver ion release upon contact with aqueous fluid, was confirmed by the in vitro formation of a 5-mm inhibition halo test against Staphylococcus aureus that is one of the most common bacteria involved in ocular infections. The approach proposed in the present study for facing implant-related ocular infections can have a significant impact in the field of ophthalmic biomaterials, suggesting a valuable alternative to the administration of antibiotics that may become ineffective due to bacterial resistance.

Differential Biological Activities of Swine Interferon-α Subtypes.

Interferons (IFNs) play a crucial role in the host's immune response and other homeostatic control actions. Three IFN types and several IFN families within the types allow for a plethora of regulatory actions. The number of distinct IFN molecules is highest among type I IFNs and, in particular, within the IFN-α family. In pigs, there are 17 IFN-α subtypes with different antiviral activities and different expression profiles; however, no data are available about biological properties other than the antiviral effector activities. Therefore, 16 porcine IFN-α genes were cloned, expressed in mammalian Chinese hamster ovary cells, and characterized for antiviral, anti-inflammatory, and MHC-modulating activities at a pre-established level of 10 IU/mL. Antiviral activity: IFN-α2, -α5, -α9, and -α10 showed the highest level of activity in a pseudorabies virus yield reduction assay. On the contrary, little, if any, activity was shown by IFN-α3, -α7, -α13, -α4, and -α15. Anti-inflammatory activity: With the exception of IFNs-α2, -α7, -α9, and -α11, all IFN-α subtypes had significant anti-inflammatory control activity in an interleukin-8 (IL-8) yield reduction assay. Gene expression analyses showed that some IFN-α subtypes can significantly downregulate the expression of IL-8, tumor necrosis factor α (TNF-α), IL-6, Toll-like receptor 4 (TLR4), ßD1, and nuclear factor-κB (NF-kB) genes, while maintaining or upregulating the expression of ßD4. Immunomodulation: A significant upregulation of class I and/or class II MHC was induced by all the IFNs under study, with the exception of IFNs-α11, -α15, and -α16, which instead significantly downregulated class I MHC. Our results indicate that gene duplications in the porcine IFN-α family underlie diverse effector and regulatory activities, being therefore instrumental in host survival and environmental adaptation. This role of IFN-α could be founded on fine-tuning and regulation of pro- and anti-inflammatory control actions after exposure to both infectious and noninfectious environmental stressors.

Biomaterials for orbital implants and ocular prostheses: overview and future prospects.

The removal of an eye is one of the most difficult and dramatic decisions that a surgeon must consider in case of severe trauma or life-threatening diseases to the patient. The philosophy behind the design of orbital implants has evolved significantly over the last 60 years, and the use of ever more appropriate biomaterials has successfully reduced the complication rate and improved the patient's clinical outcomes and satisfaction. This review provides a comprehensive picture of the main advances that have been made in the development of innovative biomaterials for orbital implants and ocular prostheses. Specifically, the advantages, limitations and performance of the existing devices are examined and critically compared, and the potential of new, smart and suitable biomaterials are described and discussed in detail to outline a forecast for future research directions.

Optimization of composition, structure and mechanical strength of bioactive 3-D glass-ceramic scaffolds for bone substitution.

Fabrication of 3-D highly porous, bioactive, and mechanically competent scaffolds represents a significant challenge of bone tissue engineering. In this work, Bioglass®-derived glass-ceramic scaffolds actually fulfilling this complex set of requirements were successfully produced through the sponge replication method. Scaffold processing parameters and sintering treatment were carefully designed in order to obtain final porous bodies with pore content (porosity above 70 %vol), trabecular architecture and mechanical properties (compressive strength up to 3 MPa) analogous to those of the cancellous bone. Influence of the Bioglass® particles size on the structural and mechanical features of the sintered scaffolds was considered and discussed. Relationship between porosity and mechanical strength was investigated and modeled. Three-dimensional architecture, porosity, mechanical strength and in vitro bioactivity of the optimized Bioglass®-derived scaffolds were also compared to those of CEL2-based glass-ceramic scaffolds (CEL2 is an experimental bioactive glass originally developed by the authors at Politecnico di Torino) fabricated by the same processing technique, in an attempt at understanding the role of different bioactive glass composition on the major features of scaffolds prepared by the same method.

Use of vitrified MSWI bottom ashes for concrete production.

Bottom ashes from a north Italian municipal solid waste incinerator (MSWI) were vitrified at 1450 degrees C without adding any vitrifying agent, then ground and sieved to different granulometry (ranging from 50 microm to 20mm), and used as filler, sand, or aggregate for concrete. Samples were characterized via slump tests (UNI 9418), alkali-silica reactivity (UNI 8520/22 and ASTM C 298), and compression strength tests (UNI 6132, 6132/72, 6686/72), and compared to reference samples obtained without vitrified bottom ashes (VBA). Our results show that vitrified bottom ashes are unsuitable as a sand substitute; however, concrete containing up to 20 wt.% of VBA filler used as a substitute for cement and up to 75 vol.% of VBA as a substitute for natural aggregate retains the same mechanical properties as reference samples. Alkali-silica or other detrimental reactions were not observed in VBA-containing concrete samples after a period of two years. The results of this work demonstrate that vitrified bottom ashes from MSWI can be used instead of natural aggregates in mortar and concrete production.