Biomedical subjects

J C Dubois

Publications and source records attributed to J C Dubois.

At least 19 recordsLinked to original sources

PubMed2001

Influence of gamma-irradiation sterilization on the structural defects of sapphire single crystals (alpha-Al(2)O(3)).

The influence of sterilization by gamma rays on the structure and the electrical behaviour of sapphire single crystal (alpha-Al(2)O(3)) was studied successively by thermoluminescence, by cathodoluminescence and by observation of the scanning electron microscope mirror effect. The mirror method allowed us to measure the capacity of an insulating material to trap electrons. The structural analysis of the alpha-Al(2)O(3) showed that there were oxygen vacancies, as well as chromium and titanium impurities. It was possible to demonstrate that these defects, especially the oxygen vacancies, are in a different state after a 30 kilogray irradiation. The valency state changes of these defects and the presence of trapped charges are accompanied by a deformation of the crystalline lattice which results in a modification of its electrical properties. At room temperature, the irradiated alpha-Al(2)O(3), unlike non irradiated alpha-Al(2)O(3), is capable of trapping electrons. It can be concluded that gamma-ray sterilization modifies the cohesive energy of alpha-Al(2)O(3), which could lead to mechanical changes (surface charge, friction, wear, fracture strength, em leader) in this material.

Aluminum Oxide↗

PubMed1999

An image analysis method for the study of cell adhesion to biomaterials.

This fluorescence image analysis method for the quantitative determination of cell adhesion on biomaterials allows bone cells labelled with propidium iodide to be counted automatically, directly on their support. The reliability of the estimation by fluorescence image analysis was validated by comparison with visual counting and with results obtained by an electronic particle counter. In this way it was possible to demonstrate that the adhesive properties of bone cells are dependent on the type of substrate--enstatite (MgO, SiO2, CaO-P2O5-Al2O3), Thermanox (modified polyethyleneterephthalate), or glass. In contrast, the spread of the cell cytoplasm, labelled with fluorescein isothiocyanate and measured by image analysis, does not vary significantly according to the substrate. The characterisation by SKIZ tessellation of the spatial cell arrangement shows that the bone cells have a random organisation on Thermanox and glass, whereas they form aggregates on enstatite.

Animals↗

PubMed1998

Effects of new machinable ceramic on behavior of rat bone cells cultured in vitro.

The behavior of cultured rat bone cells growing on modified polyethylene terephthalate (mPET), glass, and machinable ceramic substrates containing enstatite (MgO, SiO2) and glass (CaO-P2O5-Al2O3) was studied. Cell attachment was measured directly on the substrates using an image analysis system. Electron microscopy observations and the MTT test revealed that cells are able to spread and proliferate on the material surface, keeping a healthy ultrastructure on all materials tested in the present study. After having colonized the surface of the materials, as shown by immunocytochemistry, the cells synthesize an osteoid-like matrix composed of osteocalcin, type I collagen, and fibronectin fibrils. The titration of alkaline phosphatase activity showed that the cells grown on the ceramic exhibit a greater osteogenic activity than those grown on controls (glass and mPET). This osteogenic activity results in a mineralization of the extracellular matrix in cultures on ceramic or plastic whereas only few calcium phosphate crystallite traces were revealed by Von Kossa staining on glass. Enstatite constitutes, therefore, an environment compatible with in vitro bone cell life.

Animals↗

PubMed1987