Synthesis of Silver Modified Bioactive Glassy Materials with Antibacterial Properties via Facile and Low-Temperature Route

Innovative Codeposition of a Ag-Al2O3 Layer: An Attractive Combination of High Durability and Lack of Cytotoxicity for Public Space Applications

Today, the use of silver in surfaces for public environments is very frequent, as it ensures high antimicrobial activities, avoiding the continuous disinfection of the surfaces themselves. Similarly, thanks to its interesting combination of technological properties, anodized aluminum is widely employed in the production of components for applications in public spaces. Therefore, this work describes a simple method of the codeposition of silver and anodized aluminum to combine the remarkable properties of Al₂O₃ layers with the antibacterial performances of silver. The effect of silver in modifying the durability features of the anodized aluminum layer was evaluated by means of various accelerated degradation techniques, such as the exposure in a climatic chamber to UV-B radiation or an aggressive atmosphere simulated by the Kesternich test. These analyses showed the good compatibility between Ag and the alumina matrix, whose durability performances were not particularly influenced by silver. Furthermore, the composite layers did not express relevant cytotoxicity activity, as evidenced by Trypan blue flow cytometry analysis and microscopy observations, ensuring the possible use of this material in applications in close contact with humans. This same conclusion was reached by observing an almost negligible ionic release of Ag by the composite layers, even following severe degradation of the alumina matrix due to exposure to a particular acid solution. In conclusion, this work presents an innovative material that can be used in public spaces, thanks to its interesting combination of high durability and low cytotoxicity.

Durability of Acrylic Cataphoretic Coatings Additivated with Colloidal Silver

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

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

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