SYNOPSIS
Purpose: Osteoblasts, osteogenic factors, and scaffold material are needed in bone regeneration. We examined the physical characteristics and internal structure of porous coral as a scaffold material. Methods: Dried blocks (diameter 4 mm, height 10 mm) of porous coral (stony coral and velvet finger coral) were immersed in 1N NaOH to remove protein. We then measured the specific gravity of the dry blocks, the proportion consisting of internal cavities, and the physical strength (compressive strength, hardness) of the blocks when wet, and compared the physical strength of the coral with that of femurs of Wistar rats. We also observed the exoskeleton and status of internal cavities in these 2 types of coral using micro-CT. Particles of both types of coral were added to human-derived fibroblasts and vascular endothelial cells. Then they were co-cultured for 10 days and the cytotoxicity of these materials was studied. Results: The specific gravity, proportion consisting of cavities, and internal diameters of these cavities were 1.29, 53.1%, and 500 µm, respectively, for stony coral, and 1.40, 50.4%, and 100-200 µm for velvet finger coral. The compressive strength and hardness of stony coral (11.2 MPa, 44.9) and velvet finger coral (12.4 MPa, 61.7) were about 21% and 66% those of rat femur (55.4 MPa, 80.4), respectively. Little cytotoxicity was seen in either of the coral particles in the cell culture test. These findings suggest that these corals would be useful as scaffolding material.

Key words: Coral, Skeleton structure, Scaffold, Physical strength, Biocompatibility