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Polyphenols are actually achieving an increasing interest due to their potential health benefits, such as antioxidant, anticancer, antibacterial and bone stimulation abilities. However their poor bioavailability and stability hamper an effective clinical application as therapeutic principles. The opportunity to couple these biomolecules with synthetic biomaterials, in order to obtain local delivery at the site of interest, improve their bioavailability and stability and combine their properties with the ones of the substrate, is a challenging opportunity for the biomedical research. A silica based bioactive glass, CEL2, has been successfully coupled with gallic acid and natural polyphenols extracted from red grape skins and green tea leaves. The effectiveness of grafting has been verified by means of XPS analyses and the Folin&Ciocalteu tests. In vitro bioactivity has been investigated by soaking in simulated body fluid (SBF). Surface modification after functionalization and early stage reactivity in SBF have been studied by means of zeta potential electrokinetic measurements in KCl and SBF. Finally the antioxidant properties of bare and modified bioactive glasses has been investigated by means of the evaluation of free radical scavenging activity by Electron Paramagnetic Resonance (EPR)/spin trapping technique after UV photolysis of H2O2 highlighting scavenging activity of the bioactive glass.

Bacterial contamination and bone tissue overgrowth are currently the main issues for temporary fixation devices. The aim of this research is the development of innovative inorganic coatings able to reduce bacterial adhesion and bone tissue overgrowth without hampering cytocompatibility. 316L stainless-steel, Titanium grade4 and Titanium grade5 were selected as substrates, as currently used in temporary fixation devices. Starting from previous results on silica, alumina and zirconia were selected as coating matrices, according to their higher chemical stability, reduced bacterial adhesion and possible reduction of tissue overgrowth. Coatings were produced by co-sputtering. Coating adhesion was evaluated by tape test. Samples were immersed in ultrapure water up to 28 days to investigate silver release and chemical stability in fluids. Surface roughness was measured by contact profilometry. Surface wettability was determined by contact angle measurements and antibacterial activity was studied against antibiotic resistant S aureus. The research demonstrates the possibility to obtain coatings with roughness lower than the critical threshold for the increase of bacterial adhesion (0.2 µm) and optimal mechanical adhesion to metallic substrates. Coating chemical stability in water is strongly affected by the coating matrix composition. Silver release can be tailored to obtain antibacterial and biocompatible surfaces.

In this work, the bioactive glass 45S5 (also known by its commercial name Bioglass®) was successfully dip-coated by a natural derived biopolymer, increasing its apatite-forming ability. The biopolymer was shown to accelerate the first stages of bioactivity, inducing a fast transition to step 4 (formation of amorphous Ca P layer) in the apatite-forming ability mechanism. The faster precipitation of Ca/P crystals in the coated samples resulted in the formation of an intermediate amorphous octacalcium phosphate, which later transforms into an apatite layer with high thickness. The effect of the thickness of the coating was also studied on samples coated with polymer suspensions of different concentrations (0.15% and 1.5%, w/v), revealing that the kinetics of formation of the final hydroxycarbonate apatite layer increases with the thickness of the coating. The mechanism by which this apatite-forming ability is accelerated was also investigated, revealing that certain functional groups present in the structure of the polymer allow it to act as an organic matrix and preferential nucleation site for the growth of the hydroxycarbonate apatite layer.

This work describes the chemical, mechanical and antibacterial properties of a novel silver nanocluster/silica composite coating, obtained by sputtering, on textiles for use in nuclear bacteriological and chemical (NBC) protection suites and for aerospace applications. The properties of the coated textiles were analyzed in terms of surface morphology, silver concentration and silver release in artificial sweat and synthetic tap water, respectively. No release of silver nanoparticles was observed at given conditions. The water repellency, permeability, flammability and mechanical resistance of the textiles before and after sputtering demonstrated that the textile properties were not negatively affected by the coating. The antibacterial effect was evaluated at different experimental conditions using a standard bacterial strain of Staphylococcus aureus and compared with the behavior of uncoated textiles. The coating process conferred all textiles a good antibacterial activity. Optimal deposition conditions were elaborated to obtain sufficient antibacterial action without altering the aesthetical appearance of the textiles. The antibacterial coating retained its antibacterial activity after one cycle in a washing machine only for the Nylon based textile. QC 20141205 NASLA

Surface functionalization of bioactive glasses with the enzyme alkaline phosphatase (ALP) was studied in order to combine the inorganic properties of bioactive glass (bioactivity) with the biological properties of the biomolecule (mineralization). Two different bioactive glasses (SCNA and CEL2), with different degree of bioactivity, were used as substrates for the functionalization. ALP was grafted either by direct bonding or via an organic coupling agent. The cellular response to surface-modified bioactive glass was investigated using human osteosarcoma cells (MG63, osteoblast-like). Biocompatibility of all modified surfaces was verified. Of note, the more reactive glass (CEL2), modified with ALP, showed improved mineralization ability.

In this work silica-based bioactive glass powders were doped with Cu++ ions by means of ion-exchange process and subsequently they were exposed to different chemical (tannic acid, ascorbic acid and NaOH) and physical processes (UV irradiation, thermal treatment in air or argon atmosphere) to promote the in situ reduction of Cu++ ions to Cu+ or Cu0. The obtained glasses were investigated by means of structural (X-Ray diffraction – XRD), morphological and compositional analyses (scanning-transmission electron microscopy equipped with energy dispersive spectroscopy (FESEM/STEM-EDS); moreover, glasses were subjected to in vitro bioactivity test in simulated body fluid up to 14 days to investigate the influence of the performed chemical and physical treatments on glass bioactivity. At the end of incubation time glasses were analyzed by means of FESEM-EDS and Fourier transformation infrared spectroscopy (FT-IR). The obtained results evidenced that, in general, the chemical treatments are useful to induce the formation of Cu0, while thermal treatment induce the nucleation of CuO (in air) or Cu2O (in argon). All samples maintained a bioactive behavior. At least, preliminary antibacterial effect evaluation by inhibition halo test evidenced that samples containing free Cu++ ions or Cu0 nanoparticles possess the best antibacterial effect.