Microbial adhesion on novel yttria-stabilized tetragonal zirconia (Y-TZP) implant surfaces with nitrogen-doped hydrogenated amorphous carbon (a-C:H:N) coatings

cited By 2International audienceObjectives: Biomaterial surfaces are at high risk for initial microbial colonization, persistence, and concomitant infection. The rationale of this study was to assess the initial adhesion on novel implant surfaces of Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans upon incubation. Materials and methods: The tested samples were 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) samples with nitrogen-doped hydrogenated amorphous carbon (a-C:H:N) coating (A) and 3Y-TZP samples coated with ceria-stabilized zirconia-based (Ce-TZP) composite and a-C:H:N (B). Uncoated 3Y-TZP samples (C) and bovine enamel slabs (BES) served as controls. Once the surface was characterized, the adherent microorganisms were quantified by estimating the colony-forming units (CFUs). Microbial vitality was assessed by live/dead staining, and microbial-biomaterial surface topography was visualized by scanning electron microscopy (SEM). Results: Overall, A and B presented the lowest CFU values for all microorganisms, while C sheltered significantly less E. faecalis, P. aeruginosa, and C. albicans than BES. Compared to the controls, B demonstrated the lowest vitality values for E. coli (54.12 %) and C. albicans (67.99 %). Interestingly, A (29.24 %) exhibited higher eradication rates for S. aureus than B (13.95 %). Conclusions: Within the limitations of this study, a-C:H:N-coated 3Y-TZP surfaces tended to harbor less initially adherent microorganisms and selectively interfered with their vitality. Clinical relevance: This could enable further investigation of the new multi-functional zirconia surfaces to confirm their favorable antimicrobial properties in vivo. © 2015, Springer-Verlag Berlin Heidelberg

Rhodium phosphine-phosphite catalysts in the hydrogenation of challenging N-(3,4-dihydronaphthalen-2-yl) amide derivatives

The enantioselective catalytic hydrogenation of N-(3,4-dihydronaphthalen-2- yl) amides (1) with rhodium catalysts bearing phosphine-phosphite ligands 4 has been studied. A wide catalyst screening, facilitated by the modular structure of 4, has found a highly enantioselective catalyst for this reaction. This catalyst gives a 93% ee in the hydrogenation of 1a and also produces high enantioselectivities, ranging from 83 to 93% ee, in the hydrogenation of several OMe- and Br-substituted substrates. In contrast, the structurally related enol esters 2 are very reluctant to undergo hydrogenation. A coordination study of the representative enamide 1d has shown an unusual η6-arene coordination mode, over the typical O,C,C chelating mode for enamides, as the preferred one for this substrate in a Rh(I) complex. Deuteration reactions of 1c,d indicate a clean syn addition of deuterium to the double bond without an isotopic effect on the enantioselectivity. © 2013 American Chemical Society.Peer Reviewe

Analytical criteria for use of MS/MS for determination of dioxins and dioxin-like PCBs in feed and food

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