Biomedical subjects

E Jallot

Publications and source records attributed to E Jallot.

9 recordsLinked to original sources

PubMed2001

Effect of hydroxyapatite sintering temperature on intracellular ionic concentrations of monocytes: a TEM-cryo-X-ray microanalysis study.

Hydroxyapatite used as bone replacement can lead to particle release in the implantation site. These particles interact with monocytes, which are the first immune cells to colonize the implant and an inflammatory site. Thanks to cryo-X-ray microanalysis, we can observe cells in a state close to the physiological one and we have access to diffusible ions. We paid particular attention to the potassium-to-sodium ratio, which is one of the best viability criteria. We used this method to study the interaction between three hydroxyapatite particles treated at three different temperatures (not treated, treated at 600 degrees C and 1180 degrees C), and monocytes. In the culture condition, the hydroxyapatite treated at 1180 degrees C underwent the least dissolution. We demonstrate that monocytes were altered by the three hydroxyapatite particles. The hydroxyapatite particules treated at 600 degrees C were found to be more toxic.

Bone Substitutes↗

PubMed2001

Dissolution Kinetics, Selective Leaching, and Interfacial Reactions of a Bioglass Coating Enriched in Alumina.

Bioglass coatings are interesting for developing a direct bond between prostheses and bone. But the high solubility of these materials limits their application. The addition of alumina can be used to control their solubility, but may inhibit the bonding mechanisms. In this paper, we study a bioglass in the SiO(2)-Na(2)O-CaO-P(2)O(5)-K(2)O-Al(2)O(3)-MgO system. After delays of implantation from 2 to 12 months, the bioglass/bone interface is characterized by energy-dispersive X-ray spectroscopy coupled with scanning transmission electron microscopy. Bioglass dissolution can be decomposed into three steps with selective leaching. Results show that, at 2 months after implantation, the bioglass is composed of Al, Si, Ca, and P. Alumina addition increases the coating stability without inhibiting the bonding process. Complex physicochemical reactions take place at the bioglass periphery. The coating bonds to bone through a Ca-P layer on top of a pure Si-rich layer. These phenomena are associated with bioactivity properties, which occur for up to 6 months. After 12 months, the bioglass is composed of silicon. Copyright 2001 Academic Press.

Journal Article↗

PubMed2001

Bioactive glass stimulates in vitro osteoblast differentiation and creates a favorable template for bone tissue formation.

In this study, we have investigated the behavior of fetal rat osteoblasts cultured on bioactive glasses with 55 wt% silica content (55S) and on a bioinert glass (60S) used either in the form of granules or in the form of disks. In the presence of Bioglass granules (55 wt% silica content), phase contrast microscopy permitted step-by-step visualization of the formation of bone nodules in contact with the particles. Ultrastructural observations of undecalcified sections revealed the presence of an electron-dense layer composed of needle-shaped crystals at the periphery of the material that seemed to act as a nucleating surface for biological crystals. Furthermore, energy dispersive X-ray (EDX) analysis and electron diffraction patterns showed that this interface contains calcium (Ca) and phosphorus (P) and was highly crystalline. When rat bone cells were cultured on 55S disks, scanning electron microscopic (SEM) observations revealed that cells attached, spread to all substrata, and formed multilayered nodular structures by day 10 in culture. Furthermore, cytoenzymatic localization of alkaline phosphatase (ALP) and immunolabeling with bone sialoprotein antibody revealed a positive staining for the bone nodules formed in cultures on 55S. In addition, the specific activity of ALP determined biochemically was significantly higher in 55S cultures than in the controls. SEM observations of the material surfaces after scraping off the cell layers showed that mineralized bone nodules remained attached on 55S surfaces but not on 60S. X-ray microanalysis indicated the presence of Ca and P in this bone tissue. The 55S/bone interfaces also were analyzed on transverse sections. The interfacial analysis showed a firm bone bonding to the 55S surface through an intervening apatite layer, confirmed by the X-ray mappings. All these results indicate the importance of the surface composition in supporting differentiation of osteogenic cells and the subsequent apposition of bone matrix allowing a strong bond of the bioactive materials to bone.

Animals↗

PubMed2000

In vitro effects of zirconia and alumina particles on human blood monocyte-derived macrophages: X-ray microanalysis and flow cytometric studies.

The cytocompatibility of two particulate bioceramics, zirconia and alumina, was studied using human blood monocytes driven to differentiate into mature macrophages with granulocyte macrophage-colony-stimulating factor. Changes in individual cell elemental composition, particularly sodium and potassium content, were assessed by X-ray microanalysis of ultrathin freeze-dried sections. Phagocytosis and respiratory burst of macrophages exposed to biomaterial for 7 days were analyzed under flow cytometry using uptake of fluorescent latex beads and 2'7'-dichlorofluorescien diacetate oxidation, respectively. Zirconia and alumina particles were found to decrease the intracellular potassium/sodium ratio (an index of cell vitality) significantly (p<.01) in 7-day-cultured macrophages compared to control cells cultured out of material. Phagocytosis of both ceramic particles by macrophages was followed by a concomitant decrease in cell phagocytic ability (27%) and a marked altered oxidative metabolism (>2 times reduced by zirconia and >5 times reduced by alumina). The present study clearly demonstrates that reduction of the phagocytic capacity of macrophages associated with altered oxidative metabolism caused by biomaterial particles is characterized by changes in intracellular elemental content. Thus, investigation of cellular homeostasis by electron probe microanalysis together with analysis of functional changes may improve estimation of biomaterial cytocompatibility.

Aluminum Oxide↗

PubMed2000

Integration of dense HA rods into cortical bone.

HA ceramics are daily used in human surgery for bone healing partly due to their ability to integrate into bone. They are generally used under a macroporous form. The behaviour of dense HA after implantation is not so well known. We implanted within cortical sheep femurs dense pure HA-ceramics cylinders for periods from 2 weeks to 18 months. The samples were then sectioned and examined using back-scattered and secondary SEM and the interface was analysed using EDS. Histomorphometry measurement was also performed using an image analysis device coupled to a light microscope. It appeared that the cylinders were in direct contact with immature bone after three weeks. The bone maturated within three months. The implant surface showed moderate signs of resorption and some grains were released from the surface. The resorption zone was only a few microm thick after 18 months. The bulk ceramic contained default zones of increased porosity. They can constitute fragile zone when located close to the surface in which the resorption rate is increased. We conclude that dense pure HA is poorly degraded when implanted in cortical bone. Degradation depends on the defaults found on the ceramic structure and the remodelling of bone surrounding the material.

Biocompatible Materials↗

PubMed1998

[Biomaterials in an osteo-articular environment. Report of 129 anatomoclinical cases].

Actually, there is a range of biomaterials which are synthetic or metallic (or the both). They are employed as prosthesis (biostability property) or as bone graft (bioresorbability property). To understand the interactions between cells and such materials, we studied with human bone cellular cultures the cytologycal, immunohistochemical, cytogenetical and ultrastructural aspects of biomaterials in cell cultures. This paper concerns bioceramics like Pyrost, coral, biosorb, oxbone and polymers like polyethylene and silicones. The aim of this work is to evaluate the efficiency of some biomaterials. We found that porosity is primordial to promote biodegradation of bone substitutes. In fact, the biomaterials is integrated and lead to an osteoconduction, an osteoformation and finally an osteoinduction. Our observations show the implant resorption and ossification occurring in the matrix which penetrate it.

Biocompatible Materials↗

PubMed1996

Diffusion of mineral elements evaluated by PIXE at the bone-coral interface.

Substituting the tissue of human organs with biomaterials is problematic. However, its importance and relevance justify all the efforts made. An interdisciplinary approach is required. We report on our study of a product for bone substitution. Coral is a natural product, the interest of which we have already demonstrated in our previous work. Following sterilization, natural coral was implanted in sheep femurs. We regularly extracted the implants from the femurs to study the kinetics of elemental mineral transformation of the bone substitutes. For the first time ever, and thanks to the PIXE method (particles induced X-ray emission), we were able to measure the concentration of mineral elements at different time intervals after implantation over a whole cross-section. We found a discontinuity of the mineral elements (Ca, P, Sr, Zn, Fe) at the interface between the implant and the receiver. This shows that the osseous attack is not global but, on the contrary, centripetal. Moreover, the fit of the concentration time course indicates that the kinetics of ossification are different for each atomic element and characterize a distinct biological phenomenon. Our analyses confirm the biocompatibility and the ossification of the implanted coral.

Animals↗

PubMed1996

Resorption kinetics of osseous substitute: natural coral and synthetic hydroxyapatite.

Coral and hydroxyapatite may be used as substitution biomaterials for bone grafts. In this work, we extracted the implants from the femora to study the kinetics of elementary mineral transformation of the osseous substitutes. The use of physical analysis methods such as PIXE (particle-induced X-ray emission) shows that coral and hydroxyapatite, after their implantation in vivo, reach a mineral composition comparable with that of bone. For the first time we have measured the concentration of mineral elements, at different time intervals after implantation, along a cross-section. The distribution according to mineral elements (Ca, P, Sr, Zn, Fe) in the implant, in the receiver site and also at the interface, showed that the kinetics of coral resorption was faster than that of hydroxyapatite; in the same way, the osseous attack was not global but, rather, centripetal.

Animals↗

PubMedDate not supplied

Correlation between hydroxyapatite osseointegration and Young's Modulus.

From the standpoint of hard tissue response to implant materials, calcium phosphate is probably the most compatible of materials known. During the last few years, much attention has been paid to hydroxyapatite and beta-tricalcium phosphate as potential biomaterials for a bone substitute. Good implantation of biomaterials in the skeleton is evidenced by an ability to reach full integration of the non-living implant with living bone. The aim of this study is to correlate hydroxyapatite osseointegration with Young's Modulus. Cylinders (5-6 mm in diameter) of these ceramics were packed into holes made in the femur diaphysis of a mature sheep. At 2, 4, 8, 12, 16, 20, 28, 36 and 48 weeks after the operation, samples of the bone/implant interface were embedded in polymethylmethacrylate. We used the PIXE method (Particles Induced X-rays Emission) to measure the distribution of mineral elements (Ca, P, Sr, Zn, Mn and Fe) at the bone/implant interface. At 4, 8, 12, 16, 20, 28, 36 and 48 weeks after implantation we studied Young's Modulus on a biopsy of the ceramic. Young's Modulus increased with time after implantation and is linked with biomaterials integration into cortical bone.

Animals↗