Preparation And Study Of HA Microspheres As Delivery System For Antibiotics

Calcium phosphate-based drug delivery systems have been studied abroadly in recent years because of their good biocompatibility. The purpose of this study is to investigate the nanostructure hydroxyapatite powder prepared by sol-gel method and the process of the preparation HA microspheres. In addition, the rate of drug release of porous HA microspheres in vitro was also studied in this experiment.Nano HA powder was prepared by sol-gel method and its characteristics were detected by DSC, XRD analysis to determine the sintering temperature and crystallization. During the process of microspheres, the effects of ratio of gelatin and HA, temperature and stirring rate on HA microspheres were investigated. After drug loading the microspheres were dipped in PBS-HCl solution for 20 days at 37oC and pH 7.4 for drug release.The results showed that a high pH could shorten the times from sol to gel. HA crystallization can be formed when the dried gel was calcined at 350oC for 200 min. At 600oC, the dried gel could transform into HA crystallization completely. TEM analysis shows that the size of HA is in the range of 30 to 50nm. When sinterred at 950 oC and 1150 oC, XRD analysis shows no new phase appearance. But we found there was hydroxyl reaction occurred through IR analysis. These show that the HA made by sol-gel method can crystallise at low temperature and has high temperature stability.Using pseudo-double-emulsion method to prepare HA microspheres, we found that temperature is the key factor that affects the morphology of microspheres in the course of the experiment. So we prepared the double-emulsion at 0oC temperature. Aqueous solution of 10% gelatin content was prepared by dissolving 3g gelatin in 30ml distilled water at 39oC. Fine HA powder was added to the above solution in amounts of 1g HA powder per 4~10ml of gelatin solution. After that, the HA/gelatin slurry was dispersed in 150ml of oil in a beaker by stirring with a glass paddle stirrer at 100~400 r/pm. Then the precipitated beads were washed in acetone followed by ethanol and dried in air. There was no collapsibility happenning after calcined at 1200 oC. It was found that with the increase in the proportion of HA/gelatin the microspheres become more regular, and the microspheres size becomes smaller. we select the regular microspheres as drug delivery for Gentamicin sulfate. When the microspheres with drug were coated byα-TCP, the drug release can be time-controlled.