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.

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In this study, multifunctional stratified antibacterial and bioactive coatings were deposited and characterised. Initially, PEEK/bioactive glass (BG)/ mesoporous bioactive glass nanoparticle (MBGN) layers with a thickness of 110–120 μm were deposited on stainless steel substrates using electrophoretic deposition (EPD). Thin silver nanocluster-silica composite layers with a thickness of 70–155 nm were then deposited by radio frequency (RF) co-sputtering on the previously deposited EPD coatings. The deposition was carried for two different sputtering times (20 min and 40 min), which led to different layer thicknesses. PEEK/BG/MBGNs coatings were also deposited via single-step EPD. A comparison between the physicomechanical and biological characteristics of single layer PEEK/BG/MBGNs composite coating and bilayer Ag-PEEK/BG/MBGNs is presented. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX) indicated that silver nanoclusters were homogeneously distributed in the multilayered EPD/RF coatings. An apatite-like structure was formed on the surface of the coatings upon immersion in simulated body fluid (SBF) after 1 day. Silver nanoclusters embedded in the silica matrix as a top layer provided controlled release of silver ions which led to a potent antibacterial effect against E. coli and S. carnosus. Single layer coatings exhibited a burst release of Ag ions, which led to antibacterial effects but were toxic to osteoblast cells. Finally, the results of WST-8 assays confirmed that the multi-structured coatings allow osteoblast-like cells to proliferate and attach strongly on the surface of the coatings.

Porous glass-ceramics were produced by sponge replication for possible use as orbital implant materials, characterized from a morphological viewpoint, and compared to commonly used devices. Favorable characteristics of these new materials for ocular applications include total porosity above 50 vol.%, presence of open and large macropores (>200 lm) that could potentially allow fibrovascular tissue ingrowth, and submicronic surface roughness which is significantly lower than that of commercial "gold standard" alumina implants. The last feature is key to limit the risk of postoperative conjunctival abrasion and to achieve clinical success. Therefore, these glass-ceramic porous materials are highly promising alternatives to existing ceramic orbital implants.

Nowadays, the drive for green products has undergone a rapid increase following the global ecoawareness and the severe regulations aimed at preventing the environment from further damage. The use of ecosafe constituents in materials for harsh applications, such as brake pad systems, can be a possible solution for reducing health hazards arising from particle release during braking. Based on this, the present study provides a bibliographic review of green alternative constituents for friction material formulation, focusing the attention on their influence on the tribological properties of the final composites. The traditional materials still used in commercial brake pads are shortly described, with the aim to provide an overview of the current situation. In the final part of the review, following the trend of circular economy, works dealing with the use of waste as an ingredient of friction materials are also reported. The whole literature screening points out that much work is still required to obtain completely green friction materials. Indeed, few works dealing with the phenolic resin replacement, proposing inorganic ecosafe materials such as geopolymers, are present. On the contrary, the use of natural fibers is widely investigated: palm kernel, flax, agave and aloe can be identified as promising constituents based on the literature results and the generated patents.