Calcium Phosphate Glass-Ceramics As Drug Delivery Biomaterials And Degradation Studies In Vitro

Replacements of biological tissues, controlled drug delivery represents new development of biomaterials research. The purpose of this study was to investigate that the Sr containing calcium phosphate glass-ceramic as a potential biomaterial for drug delivery. The glass-ceramic system was selected based on CaO-P₂O₅-Na₂O and an inert metal oxide SrO, with CaO/P₂O₅ molar ratio=1.25. Also, CaO-P₂O₅-Na₂O glass-ceramic system prepared by melting-sintering method was investigated as comparable system. The CPSN (CaO-P₂O₅-SrO-Na₂O) glass-ceramic was prepared by melting-sintering way and sol-gel way, respectively. In order to evaluate the degradation of the glass-ceramic prepared, degradation studies were carried out after dipped in in PBS-HCl solution for 26 days at 37℃, pH 7.4, which was close to that found in human. Concentration of Ca²⁺ in the PBS-HCl solution was tested by Atomic Absorption Spectrometer with different days.Using XRD analysis, biocompatibleβ-Ca2P2O7 (β-DCP) phase and small amount of Ca3(PO4) and Na2CaP2O7 were clearly identified from the CPSN glass-ceramic prepared by melting-sintering method. The compact is densified successfully with few closed pores. By soaking in PBS solution, the concentration of calcium ion increased from 3 days to 7 days and then a decrease was observed until 16 days. Some new phases—hydroxyapatite-like (HA-like) and Sr-hydroxyapatite (Sr-HA) as dominant phases detected by XRD—were formed on the surface of the glass-ceramic samples during degradation. At the meantime, formation of mineralized layer with high density which consisted of HA-like and Sr-HA containing random oriented fine crystals was observed by SEM. The average strength of CPSN glass-ceramic sample determined by 3-point bending method was 40～50MPa.Biocompatibleβ-Ca2P2O7 (β-DCP) and NaCaPO4 phase were clearly identified from the CPSN glass-ceramics prepared by sol-gel method, using XRD analysis. The size of the granules was smaller in this glass-ceramic, which is different from one prepared by melting-sintering way. By soaking 3 days in PBS solution, the concentration of calcium ion reached peak value and then a severe decrease was observed until 11 days. With time increased, fluctuation of ion concentration curve was observed. It demonstrated that persistent degradation occurred on this glass-ceramic. And the Sr-HA mineralized layer was formed on the surface of the glass-ceramic samples during degradation. The bending strength of this CPSN glass-ceramic sample appeared a decrease, was about 19～24MPa.