Bioeutectic® ceramics for biomedical application obtained by laser floating zone method. In vivo evaluation

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license.In this study, the Bioeutectic® blocks were inserted into the critical size defects of eight rabbits, using both tibiae, and the physical and chemical nature of the remodeled interface between the Bioeutectic® implants and the surrounding bone were performed at four and 15 months. The results showed a new fully mineralized bone growing in direct contact with the implants. The ionic exchange, taking place at the implant interface with the body fluids was essential in the process of the implant integration through a dissolution-precipitation-transformation mechanism. The study found the interface biologically and chemically active over the 15 months implantation period. The osteoblastic cells migrated towards the interface and colonized the surface at the contact areas with the bone. The new developed apatite structure of porous morphology mimics natural bone. © 2014 by the authors.The authors wish to acknowledge funding from the European Community at the 7th Framework Program EU No. 314630-UV Marking and Generalitat Valenciana (GVA) within the Project ACOMP/2009/173.Peer Reviewe

LptO (PG0027) is required for lipid A 1-phosphatase activity in Porphyromonas gingivalis W50

ABSTRACT Porphyromonas gingivalis produces outer membrane vesicles (OMVs) rich in virulence factors, including cysteine proteases and A-LPS, one of the two lipopolysaccharides (LPSs) produced by this organism. Previous studies had suggested that A-LPS and PG0027, an outer membrane (OM) protein, may be involved in OMV formation. Their roles in this process were examined by using W50 parent and the Δ PG0027 mutant strains. Inactivation of PG0027 caused a reduction in the yield of OMVs. Lipid A from cells and OMVs of P. gingivalis W50 and the Δ PG0027 mutant strains were analyzed by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS). Lipid A from W50 cells contained bis-P-pentaacyl, mono-P-pentaacyl, mono-P-tetraacyl, non-P-pentaacyl, and non-P-tetraacyl species, whereas lipid A from Δ PG0027 mutant cells contained only phosphorylated species; nonphosphorylated species were absent. MALDI-TOF/TOF tandem MS of mono-P-pentaacyl ( m / z 1,688) and mono-P-tetraacyl ( m / z 1,448) lipid A from Δ PG0027 showed that both contained lipid A 1-phosphate, suggesting that the Δ PG0027 mutant strain lacked lipid A 1-phosphatase activity. The total phosphatase activities in the W50 and the Δ PG0027 mutant strains were similar, whereas the phosphatase activity in the periplasm of the Δ PG0027 mutant was lower than that in W50, supporting a role for PG0027 in lipid A dephosphorylation. W50 OMVs were enriched in A-LPS, and its lipid A did not contain nonphosphorylated species, whereas lipid A from the Δ PG0027 mutant (OMVs and cells) contained similar species. Thus, OMVs in P. gingivalis are apparently formed in regions of the OM enriched in A-LPS devoid of nonphosphorylated lipid A. Conversely, dephosphorylation of lipid A through a PG0027-dependent process is required for optimal formation of OMVs. Hence, the relative proportions of nonphosphorylated and phosphorylated lipid A appear to be crucial for OMV formation in this organism. IMPORTANCE Gram-negative bacteria produce outer membrane vesicles (OMVs) by “blebbing” of the outer membrane (OM). OMVs can be used offensively as delivery systems for virulence factors and defensively to aid in the colonization of a host and in the survival of the bacterium in hostile environments. Earlier studies using the oral anaerobe Porphyromonas gingivalis as a model organism to study the mechanism of OMV formation suggested that the OM protein PG0027 and one of the two lipopolysaccharides (LPSs) synthesized by this organism, namely, A-LPS, played important roles in OMV formation. We suggest a novel mechanism of OMV formation in P. gingivalis involving dephosphorylation of lipid A of A-LPS controlled/regulated by PG0027, which causes destabilization of the OM, resulting in blebbing and generation of OMVs. </jats:p

Structural changes during crystallization of apatite and wollastonite in the eutectic glass of Ca3(PO4)2-CaSiO3 system

In this study, a bioactive glass of eutectic composition based on Ca(PO)-CaSiO system was prepared and investigated. It was found that by controlling the nucleation and growth of crystals, a glass-ceramics free from cracks, containing one or two crystalline phases, and of controlled nano- to microscale microstructure can be obtained. Heat treatment of the parent glass produces various calcium phosphates (Ca-deficient apatite and α-tricalcium phosphate) and calcium silicates (pseudo-wollastonite and/or wollastonite-2M) plus amorphous phases. By combining a number of experimental techniques like P and Si magic angle spinning nuclear magnetic resonance spectroscopy, scanning and transmission electron microscopy, energy-dispersive X-ray spectrometry, and Rietveld analysis of X-ray diffraction patterns, a crystallization model was derived, capable of explaining the observed structural and microstructural changes. The determination of amorphous or crystalline phases enabled to produce time-temperature-transformation plots. The structural role on the behavior of these materials and its impact on their in vitro bioactivity are also discussed.The authors acknowledge support of the E.U. COST Action MP 1301 Newgen (http://www.cost-newgen.org/)

Preparation of silicon carbide by electrospraying of a polymeric precursor

Silicon carbide (SiC) coatings and films have been prepared for the first time by electrostatic atomization of a solution of a polymeric precursor and deposition on to alumina and zirconia substrates. The deposits were heated to 13008C prior to their examination by X-ray energy-dispersive spectra and selected-area diffraction in scanning and transmission electron microscopes. The results show that these coatings and films are crystalline and probably consist of co-existing a- SiC and b-SiC phases

The origin of long-period lattice spacings observed in iron-carbide nanowires encapsulated by multiwall carbon nanotubes

Structures comprising single-crystal, iron-carbon-based nanowires encapsulated by multiwall carbon nanotubes self-organize on inert substrates exposed to the products of ferrocene pyrolysis at high temperature. The most commonly observed encapsulated phases are Fe3C, α-Fe, and γ-Fe. The observation of anomalously long-period lattice spacings in these nanowires has caused confusion since reflections from lattice spacings of �0.4 nm are kinematically forbidden for Fe3C, most of the rarely observed, less stable carbides, α-Fe, and γ-Fe. Through high-resolution electron microscopy, selective area electron diffraction, and electron energy loss spectroscopy we demonstrate that the observed long-period lattice spacings of 0.49, 0.66, and 0.44 nm correspond to reflections from the (100), (010), and (001) planes of orthorhombic Fe3C (space group Pnma). Observation of these forbidden reflections results from dynamic scattering of the incident beam as first observed in bulk Fe3C crystals. With small amounts of beam tilt these reflections can have significant intensities for crystals containing glide planes such as Fe3C with space groups Pnma or Pbmn. © Microscopy Society of America 2013