Preparation And Properties Of Porous Hydroxyapatite Microspheres

Hydroxyapatite has been studied abroadly as filling material in bone repairing. It is a major inorganic component of bone matrix, also hydroxyapatite has excellent biocompatibility and osteoconduction. However, it is a rather inert material with no or little intrinsic osteoinductive activity. Therefore hydroxyapatite itself can not induce the formation of new bone matrix, furthermore this material can not satisfy the physiological need for recipient. In the present study, a composite microsphere was prepared by loading rhBMP-2 into porous hydroxyapatite microspheres with an internal cavity. The rhBMP-2 gets the ability of inducing the formation of new bone matrix. A series of experiments had been accomplished as follows:1. Using self-synthesizing hydroxyapatite as raw materials, the hydroxyapatite and gelatin composite microsphere has been prepared in a gelatin/water/oil system via an emulsion method. Porous hydroxyapatite microsphere has been fabricated after the gelatin was eliminated from the composite microsphere through sintering treatment. HA raw material and obtained microsphere were characterized by TEM, XRD, TG, SEM and Mercury determination. The results showed that prepared HA raw materials were nanorod and HA microspheres were porous and had an average diameter of 800±200μm or so. With the increase of gelatin content in the emulsion system, porosity of HA microsphere increased. An internal cavity appeared in the microsphere when the weight ratio of HA and gelatin in the emulsion system reached to 4:6.2. Ibuprofen as model drug was loaded in those porous hydroxyapatite microspheres under vacuum. The release kinetics of those hydroxyapatite and ibuprofen composite microspheres was obtained by testing the content of ibuprofen which was released in PBS. The experiment was carried out in the shaker at 37℃. The results showed that all those three kind of porous hydroxyapatite microspheres got the ability of sustained release. The content of loaded Ibuprofen and the continous release time of Ibuprofen from those porous hydroxyapatite microspheres were increased with the increase of gelatin content in the emulsion system.3. rhBMP-2 as the drug was loaded in the porous hydroxyapatite microspheres which had the most loading content and the longest continous release time under vacuum. The biocompatibility of the composite microsphere was assessed by examining the expression of ALP of osteoblast MG-63 cells. The results showed that the HA/rhBMP-2 can promote the ALP express. Therefore this composite could promote the differentiation of osteogenic. So the HA/rhBMP-2 composite microsphere was a satisfied biomaterial.