Chantal Damia

Importance of dynamic culture for evaluating osteoblast activity on dense silicon-substituted hydroxyapatite.

This paper reports an investigation on human osteoblast-like cells (SaOs-2) seeded onto pure hydroxyapatite (HA) and silicon-substituted HA (SiHA) tablets under static and dynamic culture conditions. The biological characterizations were conducted in classical static conditions in multi-wells plates, and in a perfusion bioreactor that permits continuous circulation of culture medium at 2 mL/h. The morphology, proliferation and differentiation of osteoblastic cells were examined for the two types of samples in the both culture conditions after 1, 3 and 8 days. Under dynamic conditions, cells cultured on SiHA surfaces showed a faster adhesion process and the formation of longer and thinner focal adhesions than in static conditions. The number of cells grown onto both ceramic surfaces was higher in dynamic conditions when compared with static conditions. Moreover, a higher activity of alkaline phosphatase was found for cells seeded under dynamic conditions. Our findings suggest that the application of perfusion culture system on cells cultured on dense substrates is valuable for predicting in vivo behaviour of cells on biomaterials.

Surface transformation of silicon-doped hydroxyapatite immersed in culture medium under dynamic and static conditions

A comparative study of in vitro bioactivity of hydroxyapatite (HA) and silicon-doped hydroxyapatite (SiHA) has been carried out by immersion in a cell culture medium with or without fetal bovine serum during 14 days in static and dynamic conditions. A specific bioreactor was developed for the experiments in dynamic conditions. Ceramic surface transformations were characterized by electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy before and after immersion. The monitoring of calcium, phosphate and proteins in immersion medium was also done during the experiment. The two hydroxyapatite surfaces immersed in cell culture medium under dynamic conditions were found to be more probably covered by a new Mg-enriched Ca-deficient apatite layer than surfaces immersed under static conditions. These results suggest that dynamic procedure and medium with serum macromolecules seem to be more adequate to predict the in vivo activity of bioceramics. Moreover, SiHA presented a higher capacity of protein adsorption.

β-TCP porous pellets as an orthopaedic drug delivery system: ibuprofen/carrier physicochemical interactions

Abstract Calcium phosphate bone substitute materials can be loaded with active substances for in situ, targeted drug administration. In this study, porous β-TCP pellets were investigated as an anti-inflammatory drug carrier. Porous β-TCP pellets were impregnated with an ethanolic solution of ibuprofen. The effects of contact time and concentration of ibuprofen solution on drug adsorption were studied. The ibuprofen adsorption equilibrium time was found to be one hour. The adsorption isotherms fitted to the Freundlich model, suggesting that the interaction between ibuprofen and β-TCP is weak. The physicochemical characterizations of loaded pellets confirmed that the reversible physisorption of ibuprofen on β-TCP pellets is due to Van der Waals forces, and this property was associated with the 100% ibuprofen release.

Synthesis of Si-Substituted β-Tricalcium Phosphate Ceramics with Controlled Composition

Pure b-tricalcium phosphate (bTCP) and Si-substituted b-tricalcium phosphate powders with compositions ranging from x = 0.01 to 0.20 were synthesized using a wet precipitation method. The results showed that the addition of Si decreased the maturation time of single-phase Si-substituted bTCP. For longer maturation time, other phases were observed such as hydroxyapatite (HA) and a-tricalcium phosphate (aTCP). The Si incorporation was confirmed by X-ray diffraction with Rietveld refinement, indicating an increase of the lattice volume from 3524.88 Å3 for pure bTCP to 3527.41 Å3 with increasing Si content.