Développement et applications des biocéramiques

DCPD, dicalcium phosphate dihydrate (CaHPO4•2H2O) reacts with fluoride ion in an aqueous solution, and forms fluorapatite (FAp, Ca10(PO4)6F2). In previous study, we have found that DCPD does not react with fluoride ion directly, but show few hours of induction period by reaction with fluoride. In this study, effect of hydroxyapatite (HA, Ca10(PO4)6(OH)2) on the reactivity of DCPD with fluoride ion was investigated. By mixing HA with DCPD, it was appeared that the induction period of the reaction was shortened. Morphology of the obtained FAp was similar to HA paricles. We carried on coating of HA on the DCPD particle by soaking DCPD in simulated body fluid (SBF, Kokubo Solution). By coating HA on DCPD particles, particle morphology of the obtained FAp was consistency to the DCPD particles. These results suggest that the shape and particle size of FAp after reaction of DCPD is controllable by DCPD particle as template, and coating with HA.

The composition of Hydroxyapatite (HAp) is expressed by the formula Ca₁₀(PO₄)₆(OH)₂. Many reports have been published on the synthesis of HAp in which Ca ions are substituted by various cations (e.g., Sr, Ba). On the other hand, studies on the synthesis of sulfate-ion-substituted hydroxyapatite (SAp) have rarely been conducted. The present study investigated the conditions for the synthesis of SAp from amorphous calcium phosphate (ACP, Ca₃(PO₄)^2- nH₂O) as the starting material, which can readily incorporate various ions into its structure. Sodium sulfate (Na₂SO₄) was added to ACP, and then, the mixture was hydrothermally processed at 220°C for 3 h. SAp obtained under these conditions had a Ca-deficient-type HAp structure. The SO₄/PO₄ molar ratio in SAp increased with increasing amounts of added Na2SO4, reaching a maximum value of 0.5, meaning that 1/3 of the PO₄^3- ions contained in HAp were substituted by SO₄^2- ions.

Restoration and protection of tooth enamel are of great importance in operative and conservative dentistry. Using a Pulsed Laser Deposition (PLD) method, we have successfully created a freestanding flexible double-layered sheet composed of a Hydroxyapatite (HAp) layer (4 m in thickness) coated with a Tricalcium Phosphate (TCP) layer (500 nm). In order to apply the newly developed HAp/TCP sheet to the restoration and protection of tooth enamel, the adhesive characteristics of the HAp/TCP sheet on the enamel were evaluated mechanically and microstructurally in the present study. The adhesive strength (5.7 MPa) between the HAp/TCP sheet and enamel was markedly higher than that (1.9 MPa) between the mono-layered HAp sheet and enamel. The electron microscopic observation revealed that HAp/TCP sheet was widely fused with the enamel. Therefore, the double-layered HAp/TCP sheet can be used as a material to promote the repair of tooth eruption and to maintain healthy dentine.

Composite scaffolds of Polyvinyl Alcohol (PVA) and/or quaternary bioactive glass (46S6 system) containing 5, 10 and 20 wt % ciprofloxacin were prepared by lyophilisation technique. The porosity of the prepared scaffolds was measured by liquid displacement, Hg-porosimeter and SEM. The structure and the nature of chemical bonds between atoms were examined by XRD and FTIR. They confirmed the incorporation of ciprofloxacin into the scaffolds. Biodegradation rate and drug release behaviour were conducted in Phosphate Buffer Saline (PBS) at pH 7.4. A porous scaffold has been obtained with porosity up to 85%. By increasing the glass contents and drug concentration in the prepared scaffold the porosity and the degradation rate decrease however, the compressive strength was enhanced. A sustained drug release pattern was observed from the optimized scaffold with a quasi-Fickian diffusion mechanism and it was able to deliver the drug in a prolonged release pattern which offers a distinguish treatment for osteomylitis as well as local antibacterial effect.

Bioactive glasses, doped with traces of copper (Cu) and zinc (Zn) were synthesized by fusion method. Cu and Zn present interesting functions for the biological metabolism through their antibacterial, anti-inflammatory and antifungal properties. Several physical methods were employed to characterize the bioactive glasses before and after immersion in a Simulated Body Fluid (SBF). The “in vitro” experiments showed that after soaking in SBF, the behavior of bioactive doped glasses are different compared to pure glass 46S6. Obtained results show that glass matrix undergoes some changes after 15 days of immersion. The non toxic character of doped glasses was confirmed after 24 hours of incubation. The kinetic of release of Cu and Zn was carried out. It highlights that Cu is more released than Zn. By SEM, the morphology of hydroxyapatite obtained with Zn-doped glass show a better crystallization compared to Cu-doped glass.

Tailor made bioceramic scaffolds in combination with the corresponding surface chemistry and biology is of great importance for a successful implantation and rapid osseo-integration. The present study investigates the fabrication of Hydroxyapatite (HA) scaffolds with defined macro porosity by means of powder based 3D-printing. In order to mime natural bone with its elastic collagen structure, the 3D-printed ceramic structures were post-treated by polymeric infiltration. Compressive Strength analysis (CS) confirmed the positive impact of an elastomeric phase on mechanical properties. 3D-printed HA scaffolds in combination with polymer result in biodegradable scaffolds with promising mechanical properties for potential use in regenerative medicine.

Some titanium containing apatite (TMA) ceramics prepared by wet synthesis was superior to Hydroxyapatite (HAp) ceramics of mechanical property and cutting performance. In this study, we investigated chemical reaction of TMA in a body environment. Each TMA or commercial Hydroxyapatite powder (HAp) was formed to circular pellets by uniaxial pressing. The specimens were heated in muffle furnace by conventional sintering process. Some TMA specimens were dispensed by alkali and heat treatment. After the treatments, the specimens were soaked in simulated body fluid (SBF: Kokubo’s solution) at pH 7.25 at 37.0°C up to 7 days. Before and after soaking in SBF, the surfaces of the samples were characterized by XRD, SEM, and ICP. After soaking in SBF for 7days, some particles were precipitated on the surface of HAp ceramics and TMA ceramics with alkali and heat treatment. Ti-containing in the crystal structure of HAp affected apatite formation in the body environment.

In order to measure the piezoelectric properties of the Hydroxyapatite (HAp) films, we have fabricated Cu/HAp/Ti or Cu/HAp/Pt structure. At first, a 1.5 m thick HAp was deposited on a Ti or Pt substrate using the KrF Pulsed Laser Deposition (PLD) method. After the HAp deposition, the HAp film was crystallized by post-annealing in nitrogen gas atmosphere and cooled slowly in an electric furnace. Then, a Cu top electrode sheet was attached on HAp film. Finally, one end of the Cu/HAp/Ti or Cu/HAp/Pt structure was clamped to compose a vibrating cantilever beam. Piezoelectric coefficients were estimated by output voltage responses of HAp films measured by a operational amplifier circuit when the Cu/HAp/Ti or Cu/HAp/Pt beam was excited by a mini-shaker at the first natural frequency of the beam. The results showed the piezoelectricity of the artificially synthesized HAp films.

Novel dentin tubule sealing technique using ultrathin Amorphous Calcium Phosphate (ACP) freestanding sheet was developed. The sheets were prepared by pulsed laser deposition technique and separated from quarts substrate by dissolving photoresist as sacrifice layer. Sheets were pasted on dentin of extracted human teeth by using calcium phosphate aqueous solution. The sheets kept wetted by artificial saliva for a few days. After drying specimens, the bonding strength between the sheets and dentin were evaluated by quasi-tensile tests. The bonding strengths between the film and dentin were enough to seal dentin tubules. After tensile test, the specimens were embedded in epoxy resin and polished for investigation of bonding boundary nature. The presence of a few microns thick bonding layer between the film and dentin was shown clearly by cross-sectional electron microgram. These results suggest that the dentin tubules may be sealed by calcium phosphate sheet without organic materials.

The pro-angiogenic potential of copper ions could increase the viability of bone forming cells within a bone substitute scaffold, and so hasten healing, by stimulating infiltration of blood vessels into the scaffold. Copper-doped hydroxyapatite with x = 0, 0.5, 0.75 and 1 in the nominal formula Ca10(PO4)6CuxOyHz was prepared by solid state synthesis. Lattice parameters increased as x was increased, consistent with formation of Cu-O species on hydroxyl sites. In FT-IR spectra, the OH stretch (3572 cm-1) and the OH libration (631 cm-1) decreased in intensity as x was increased, and a band at 771-778 cm-1 was assignable to a Cu-O stretch, characteristic of Cu+ bands between 3140 and 3450 cm-1 related to copper-disturbed OH stretching vibrations. In UV visible spectra, bands between 400 and 800 nm were assignable to d-d transitions of Cu2+. Therefore we propose that Cu is present in these materials both as Cu+ and Cu2+.

Studying the local release of strontium traces in vivo is of key interest, but calls for highly sensitive techniques besides providing an excellent (micronic) spatial resolution. In this context nuclear microprobes such as the PIXE (Particle-Induced X-ray Emission) technique, appear as powerful tools of investigation. Here, the in vivo behaviour of a Sr-delivering bioactive glass has been investigated through micro-PIXE analyses in connection with histological studies. New bone formation is observed after 6 weeks of implantation in rabbit femoral condyle. Interestingly, Sr traces are detected over a large area at the site of implantation, demonstrating the efficient release of Sr osteo inductive ions from the glass and their diffusion over several ten microns through the tissues. From its inorganic composition and content in traces of interest such as Zn, neo formed bone seems of higher quality for Sr-delivering particles compared to Sr-free particles, evidencing the positive effect of Sr in vivo.

This study aimed to determine changes in Bone Mineral Density (BMD) and bone strength of ovariectomized rats fed a synthetic diet of Mg, Zn, and F incorporated with carbonate apatite. Group 1 (n=4) was fed a Normal Mineral Diet (NMD) and Group 2 (n=4) was fed the Synthetic Diet (SD: 0.74% Ca, 0.48% P, 0.10% Mg, 365.4 ppm Zn, 51.01 ppm F and 0.27% CO3). Rats were sacrificed after eight weeks and the femur was isolated. The micro-CT results showed that values of BMD for Group 2 were higher than those of Group 1. Bone strength values of Group 2 measured by a 3-point bending test were significantly higher than those of Group 1. These results indicated that Group 2 stimulated bone quality, increased BMD and bone strength. The SD has the potential to prevent bone loss and as an osteoporosis therapy.

The effect of Fetal Bovine Serum (FBS) deprivation on survival and apoptosis of osteoblasts cultured on various calcium phosphates was studied. Test materials were two calcium alkali orthophosphates (materials denominated: GB9 and GB14), which were compared to β-tricalcium phosphate (TCP). Tissue culture polystyrene (PS) served as control. Test materials were characterized by X-Ray Diffraction and scanning electron microscopy. An apoptotic challenge assay entailing serum withdrawal was applied: MC3T3-E1 osteoblasts were cultured for 72h on the test materials in serum containing medium, followed by incubation in serum free medium for another 24h. Serum withdrawal is an apoptotic challenge, which creates a stressed environment. Cells cultured on the test specimens in serum containing medium served as control. The TUNEL Assay was employed to quantify the percentage of apoptotic cells. GB9 and GB14 displayed a significantly lower percentage of apoptotic cells than TCP. TCP had significantly fewer apoptotic cells than PS. The percentage of apoptotic cells on GB9 and GB14 was less than 10%, while the number of apoptotic cells found on the untreated control specimens ranged between 5 and 7%. These findings indicate that GB9 and GB14 endow osteoblasts cultured on them with a decreased sensitivity to apoptosis, which corresponds well with the results of previous in vitro and in vivo studies.

Calcium Deficient Apatites (CDA’s) were prepared by hydrolysis method. The CDA’s were filtered, washed and calcined at 950â�°C for 11h. X-ray diffraction demonstrated that β-TCP was obtained after calcining Mg-free CDA and β-TCMP or BCMP were obtained after calcining Mg-substituted CDAs, depending on the Mg/Ca molar ratio of the CDA. Physicochemical characterization was also performed by FT-IR spectroscopy and inductive coupled plasma. Phenolphthalein test was performed, in order to investigate the presence of calcium oxide according to the French standard NF S 94-066. SEM images assessed the morphology of the compounds. Cell viability assay (MTT), calcium nodule formation and the expression of alkaline phosphatase (ALP), osteocalcin, TGF-β1 and collagen were performed in MC3T3-E1 cell line. β-TCP, β-TCMP and BCMP obtained from hydrolysis method weren’t toxic and promoted cell proliferation, showing potential value in bone tissue engineering.