Papers by Author: Pio González

Abstract: In this research, bioactive glass powders were electrophoretically deposited on biomorphic SiC ceramic substrates. A post-deposition thermal treatment was carried out to improve the properties of the coatings. Particle size, surface morphology, composition and thickness of the coatings have been studied by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and interferometric profilometry respectively. The analysis demonstrated that the electrophoresis parameters, such as the voltage, the distance between the electrodes and the deposition time, play an important role on the thickness of the coatings. The post-deposition thermal treatment produces glass particles cohesion and leads to obtaining a homogeneous microstructure. The excellent coverage of the porous SiC surface morphology is also demonstrated. Finally, in order to assess the bioactive character of the glass coatings, in vitro test by immersion in simulated body fluid (SBF) was carried out.

Abstract: Biomorphic silicon carbide ceramics is very promising as a natural base material for biomedical applications due to their excellent mechanical-biochemical properties and biocompatible behaviour. This innovative material is produced by molten-Si infiltration of carbon templates obtained by controlled pyrolysis of biological precursors. The final product is a light, tough and high-strength material with predictable microstructure. In this study the possibility to produce biomorphic silicon carbide ceramics using marine precursors is demonstrated. Due to the great biodiversity offered by the marine medium, a previous selection of algae (Laminaria ochroleuca Bachelot de la Pylaie, Undaria pinnatifida (Harvey) Suringar, Saccorhiza polyschides (Lightfoot) Batters and Cystoseira baccata (Gmelin) Silva) and marine plants (Zostera marina L. and Juncus maritimus L.) was carried out, taking into account its microstructure, porosity and interconnectivity of each species. The bioceramization process was evaluated in three phases: original material analysis, pyrolysis process and reactive melt Si-infiltration. For each marine precursor, a detailed study by Scanning Electron Microscopy (SEM) of the natural material, the carbon preform and the final SiC biomorphic product is described. The viability to obtain biomorphic SiC ceramic material for all the selected marine precursors is discussed.

Abstract: In the present work two different hydroxyapatite nanofilms (50 and 100 nm thick) have been successfully deposited on titanium implants that were previously laser macrostructured in order to assess the influence of the thickness of nanometric calcium phosphate coatings on the osseointegration. Cylindrical implants were tested in a sheep tibia model together with titanium alloy controls achieving very good osseointegration results. Laser macrostructured titanium alloy implants have shown improved bone regeneration when coated with nanometric films of carbonated HA. The pulsed laser deposited nanofilm has promoted bone in-growth deep into the laser ablated craters. There were no significant differences between the two coating thicknesses, neither when assessed with electron microscopy or classical optical methods. This result suggests that the 50 nm coating is as effective as the 100 nm one, therefore implying that the thickness limit for such a bioactive layer to stimulate bone growth may be even further below.

Abstract: The results of a combined structural characterisation (XRD, IR, NMR, SEM, TEM) of a phosphate containing Mg-Ca silicate and a phosphate containing Na-Ca silicate glass samples are presented. The structural results are also compared with in vitro tests carried out in simulated body fluids for checking bioactivity.

Abstract: Silicon substituted Hydroxyapatite coatings were prepared by Pulsed Laser Deposition from targets made of mixtures of Hydroxyapatite with Si powder at different concentrations. The properties of the Si-HA coatings with several degrees of Si substitution were analyzed by different techniques such as FTIR, XRD, XPS and solid-state NMR. It was found that the Si incorporation causes an amorphization of the structure together with a loss of carbonate groups. Furthermore, the Si atoms are incorporated in the form of SiO4 4- groups, and H(PO4)2- appears as the predominant phosphate group.

Abstract: The bioactive properties of hydroxyapatite (HA) are well known in the implant industry and coatings of HA have been used to enhance the adhesion of living tissue to metal prostheses. Pulsed laser deposition (PLD) in a water vapour atmosphere is an appropriate method for the production of crystalline HA coatings. In this work the effect of RF plasma on thin films of HA grown by PLD at different substrate temperatures has been studied. The physicochemical properties of the films were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), showing that the incorporation of RF discharge in the deposition chamber can lead to changes in the crystallinity and deposition rate of the films but substrate temperature still plays the most important role.

Abstract: There is a need to develop new tough bioactive materials capable to withstand high loads when implanted in the body and with improved fixation, which led to the production of bioactive coatings on metallic substrates. A new approach, which consists of biomorphic silicon carbide (SiC) coated with bioactive glass, was recently presented. This new material joins the high mechanical strength, lightness and porosity of biomorphic SiC, and the bioactive properties of PLD glass films. In this work, a multiple evaluation in terms of biocompatibility of this new material was carried out starting from the biomorphic SiC morphology and porosity, following with the bioactivity of the coatings in simulated body fluid, and ending with a deep biocompatibility study with MG-63 cells. Different ranges of porosity and pore size were offered by the biomorphic SiC depending on the starting wood. The PLD glassy coatings had a high bioactivity in vitro and both the biomorphic SiC coated and uncoated presented high levels of biocompatibility.

Abstract: The aim of this study was to test the in vitro cytotoxicity of wood-based biomorphic Silicon Carbide (SiC) ceramics, using MG-63 human osteoblast-like cells. This innovative material has been recently developed and it exhibits unique mechanical properties towards their application in biomedical technology. In the solvent extraction test the SiC ceramic extracts had almost no effect on cellular activity even at 100% concentration. A similar behaviour was found for Ti6Al4V and bioactive glass, used as reference materials. The results of the cell morphology and the cellular attachment response have also demonstrated that the in vitro performance of these biomorphic SiC ceramics is qualitatively comparable to that produced by titanium alloy and bioactive glass, which seems very promising.

Abstract: The structure of silica-based glasses consists on a disrupted network of SiO4 tetrahedra where network modifiers generate non-bridging oxygen groups (NBO), that play an important role at the initial steps of the bioactive process. Infrared spectroscopy is a sensitive technique to the presence of NBO groups and glass local structure modifications. The infrared study has been complemented with a theoretical approach using the Y Stevels parameter. Moreover, the in vitro bioactivity of the glasses as a function of Y Stevels paremeter has been studied, which can be a finding of a predictive tool for bioactivity of glasses.