Formation And Mechanism Of Bone-like Apatite On Ca-P Bioceramics Surface And Their Osteo-induction

That biomaterials were endowed with a function of inducing tissue regeneration have been regarded widely.Bone-like apatite, similar to inorganic components of bone, would form on the surface of biomaterials after biomaterials were implanted into animals, including in osteo tissue and non-osteo tissue. Bone-like apatite is osteo-induction precondition to biomaterials in non-osteo tissue, and it can absorb special albumen in serum, enhance adherence and differentiation ability of osteoblast on it, and promote cell to excrete fibrinogen and accelerate osteoblast proliferation。 Many researches thought biomaterials containing bone-like apatite on its surface and albumen absorbed by bone-like apatite played an important role in bone formation. Somatoblast adhered to the surface of bone-like apatite, assembled and proliferated, and formed somatoplasm. This indicated apatite on the surface of biomaterials was advantageous to bone regeneration. However, which mainly factors would affect bone-like apatite formation? And what kinds of apatite layers were necessary in bone inductivity? That was a question that needed to be answered for inductivity study. So, effect of envirment and materials selves on formation, components and morphology of apatite would be investigated by simulation method in vitro, mechanism and osteo-inductivity ability of apatite formation was studied in this paper.Ca-P precipitation in SBF has been widely used to assess the bioactivity of bioactive biomaterials. Biomaterials were immersed into simulated body fluids(SBFs), calcium and phosphate ions and other ions in solution deposited on the surface of materials. Up to now, there were some kinds of SBFs and simulation methods, so Ca-P precipitation from different SBFs and simulation methods are different in morphology, chemical and phase component.Apatite formation in porous tricalcium phosphate in static simulation (TCP) was compared with that in dynamic simulation in this experiment. The results showed precipitates developed along TCP granules margins in static simulation, where Ca2+ and PO₄^3- ions concentration were higher, and precipitates grew equably along TCP granules in dynamic simulation. This indicated precipitates grew according to different way.Effect of flow way and flow rate of simulated body fluids on apatite formation was stusied in dynamic simulation, structure of formed apatite was determined, and mechanism of apatite formation was discussed.We designed dynamic simulation equipment according to body fluids circulation movement and body metabolism in vivo. By observing the apatite formation on the wall of holes and surface of porous Ca-P bioceramics in the new equipment, influence of the flow rate on the formation, phase component and morphological aspect of apatite precipitation were investigated.In dynamic simulation experiment, there was some crystals formation on the interior and surface shallow wall of holes of Ca-P ceramics respectively, and morphology of formed apatite was different, for flow mode of fluids in interior holes was distinguishing from that in exterior holes of ceramics. Formed crystals were also different when immersion time changed. Some conglobulation precipitation formed on the exterior wall of hole, and petal-like crystals formed on the interior wall of hole. When SBFs flow through porous ceramics, which enwrapped by permeation film, crystals on the wall of interior holes of the ceramics were similar to that on the wall of exterior holes, sheet-like crystals arranged regularly.Effect of phase component of ceramics on apatite formation on the surface of the ceramics was studied. Experiment results indicated sheet-like HA crystals grew on the surface of dense HA ceramics, and HA and OCP mixtures formed on the surface of dense HA/TCP ceramics, meanwhile HA crystals showed a preferential growthalong C-axis.Chemical component of body fluids were quite complicated, all sorts of organisms exist in body fluids besides inorganic ions. These organisms played an important role in the adjusting Ca2+ and PO₄^3- conce...