Co-authors​ :

 Mototsugu TANAKA (JAPAN), Mototsugu TANAKA (JAPAN) 

In order to realize the high-level bone regeneration surgery, it is desirable to design the artificial bones with the bioabsorbability and the mechanical properties equivalent to the bone. The artificial bones using the composite material systems consisting of collagen and the hydroxyapatite (HAp) have been developed for this application. In order to give the characteristics equivalent to the natural bone to the artificial bone, it is necessary to develop the method to design the HAp/collagen artificial bones with the microstructures equivalent to the natural bone. Therefore, we must develop the method to construct the optimized microstructures of the HAp/collagen in a bottom-up fashion. Previously, we prepared the collagen fibers using a bio-inspired method, evaluated the effect of the cross-linker concentration on their tensile strength by the micro-mechanical tests, and optimized the preparation conditions. Then, we deposited the apatite crystals on the surface of the collagen fibers prepared under the optimal conditions by the alternating immersion in a pseudo-body fluid (biomimetic deposition method), and evaluated the effect of the deposition amount of the apatite crystals on their tensile strength by the micromechanical tests. The adhesion strength between the collagen fibers and the HAps using osteonectin was also performed. As a result, the HAp/collagen composites with the excellent mechanical properties could be created. As the next step, this study aimed to optimize the microstructural factors of the HAp/collagen composite fiber bundles.
To prepare the collagen fibers, the aqueous collagen solution of 0.1 [wt%], the sodium phosphate buffer of 40[mmol/L], the sodium chloride of 1.00 - 2.00 [mol/L], the water-soluble carbodiimide (1-ethyl-3-carbodiimide hydrochloride: EDC) as the crosslinking agent and the osteonectin as the adhesive protein were used. The temperature of the mixed solution was kept as 25 [degree C], which is lower than the denaturation temperature of the fish collagen, in the hot water for about 7 days. To perform the alternating immersion, the collagen fibers were immersed in the Ca-ion rich solution (Ca solution) and P-ion rich solution (P solution) alternately. In this study, the electrophoresis method was employed for bundling. The HAp/collagen composites were placed in the electrophoresis chamber containing the sodium chloride solution. Then, the electrode connectors were set in the bath, and electrophoresis was performed. In this study, the microstructural factors, such as the crosslinking agent concentration, the HAp deposition conditions, the adhesive protein concentration and the electrophoresis conditions, were varied for the HAp/collagen composite fiber bundles. Finally, we tried to determine their optimum microstructural factors through the microstructural tensile tests.