Study On Calcium Phosphate Cement/Gelatin-Chitosan Macroporous Composite Scaffolds

In this work, novel three-dimensional macroporous calcium phosphate cement(CPC) scaffolds embedded with porous gelatin-chitosan (Gel-CS) network spongeswere synthesize to produce composite scaffolds with relatively high mechanicalstrength for bone tissue engineering. Formed composite scaffolds had multilevelporous architecture and particular "Scaffold in Scaffold" structure.The setting mechanism and calcinations/sintering characteristics of α-tricalciumphosphate (α-TCP) CPC were investigated. The CPCs completely hardened after 3days at 100% humidity and 37℃. XRD and SEM analysis revealed that theend-product of CPC was calcium deficient hydroxyapatite (CDHA) with lowcrystallinity. By heating at different temperature in air, the hardened CPCs wereremained original CDHA phase (below 700℃) or converted into β-tricalciumphosphate (β-TCP) or β-TCP/HA (above 700℃). The ceramics calcinated at 500℃and sintered at 1050℃ had relatively stable phases and high compressive strength. Asa good porogen, chitosan microspheres had less influence on setting and heatingprocesses, which burned out easily below 500℃.The macroporous CPC scaffolds were fabricated through burn-out CS microsphere(300～450μm). The characteristics of 500℃ calcinated scaffold and 1050℃ sinteredscaffold were investigated comparatively. SEM observation and porositymeasurement revealed that only partial macropores of scaffolds were interconnectedwith above 30% of mass fraction of CS microspheres. To gain better interconnectedstructure, smaller CS microsphere (76～108μm) or CS fiber (diameter 450μm, length5~8mm) were incorporated to CPCs, too. As a result, CS fiber had better contributionto interconnectivity of the macroporous scaffold compared to the smaller CSmicrospheres. With the proper ratio of CS microspheres and CS fibers, themacroporous CPCs scaffolds exhibited relatively high mechanical strength.The macroporous CPC scaffolds as obtained were immersed in the differentconcentration of Gel-CS solution under vacuum and the CPC/Gel-CS compositemacroporous scaffolds were formed by freeze-drying process with solid-liquid phaseseparation. SEM results showed that the scaffold had multilevel porous structure(1~10μm,80~150μm and 300~500μm). The compressive strength and yield modulusof the composite scaffolds were 6～10 times that of CPC scaffolds. Apatite likecalcium phosphate particles were formed on the wall of Gel-CS inside compositescaffolds after immersed in simulated body fluid (SBF) for 5 days.