Effect of geometrical structure on the in vivo quality change of a three-dimensionally perforated porous bone cell scaffold made of apatite/collagen composite.

Biodegradable artificial bone blocks with interconnective pores were prepared using a self-setting apatite/collagen composite cement as a cell scaffold for bone regenerative medicine. The biological behavior of the blocks was tested in rats, and the change in their properties after implantation was measured. One cubic block [10 mm X 10 mm X 10 mm; porous composite (PC)] was obtained from apatite cement (apatite/collagen cement; 80% of apatite:20% of collagen) with 60 interconnecting holes, 500 um in diameter. The other blocks (NC and NN) without holes were obtained from the apatite/collagen and plain apatite cements, respectively. All blocks were implanted in the rats for 56 days. Changes in the amount and density (block mineral mass and block mineral density) of the blocks were evaluated based on dual energy X-ray absorptiometry images, and the order of biodegradation was PC < NC < NN. After implantation, the blocks were removed, and subjected to an X-ray diffraction (XRD) analysis, Fourier-transformed infrared (FT-IR) spectroscopy and thermogravimetry (TG). The XRD peaks of all blocks increased significantly. TG revealed that the amount of carbonated apatite also increased with time. However, the organic component of PC depended on the implantation period, consistent with the FT-IR results. Because PC had interconnective macro- and micropores in the apatite/collagen matrices, the results indicated that soft tissue penetrated the block carbonated apatite was generated, bone remodeling was accelerated in the implant.