Carbonate apatite (CO3Ap) was synthesized at 60+1°C and pH 7.4+0.2, to develop a new biodegradable scaffold biomaterial. The synthetic CO3Ap was mixed with a neutralized collagen gel and the CO3Ap-collagen mixtures with different kinds of CO3Ap contents and porosity were frozen and dried in lyophilized into the sponges. CO3Ap-collagen mixtures were also lyophilized into sponges in a HAp frame ring with 0.5 mm pores. To examine the degree of cell
invasion, mouse MC3T3-E1 cells were grown in αMEM with 10% heat-inactivated FBS in 96-well plates containing the CO3Ap-collagen sponges at 37°C in a 5% humidified atmosphere. Under pentobarbital anesthesia, samples of UV-irradiated CO3Ap-collagen sponges with frames were surgically implanted beneath the periosteum cranii of rats. SEM observation of CO3Ap-collagen
sponges showed favorable pores for cell invasion. Approximately 50~300 µm size pores seemed to continue into the deep bottom. X-ray high-resolution microtomography revealed a clear image of 3D structure of the sponges. 70 wt% CO3Ap-collagen sponge seemed to be most favorable
biomaterial from the viewpoint of the natural bone properties. Then, to avoid the shrinkage of the sponges, we successfully made a hybridized CO3Ap-collagen sponge with a frame. When these sponge-frame complexes were implanted beneath the periosteum cranii of rats, newly created bone was observed toward the inner core of the complex from the surface of the periosteum cranii.