Control Biological Functions by Controlling Chemical Compositions and Nanostructures of Materials

We have developed a hydroxyapatite/collagen bone-like nanocomposite (HAp/Col) with a chemical composition and nanostructure similar to those of bone. Its porous body is being used clinically in Japan. When the HAp/Col is implanted into a bone defect which was caused by disease or injury, the bone is gradually (usually within about three months) replaced by the patient's own bone through "bone remodeling process," which is the normal metabolism of bone. This would be because the HAp/Col is recognized by cells as the patient's own "broken bone that needs to be repaired." In this way, controlling the chemical composition and nanostructure control the bone resorption and bone formation functions of bone-related cells. For instance, when the HAp/Col is coated on titanium, "osseointegration," a biological response to titanium, became three times faster. Regarding the HAp/Col, we are working on controlling the micro- to macro-shape to realize such new functions. On the other hand, anodization of titanium under appropriate conditions forms titanium oxide (titania) nanotubes on the surface of titanium substrate. In addition to that, we applied polarizing on these titania nanotubes to succeed to create anti-thrombus formation surface. This is a new function achieved by controlling the electrical properties in addition to the chemical composition and nanostructure. Furthermore, we have proposed a compliant test method for materials containing HAp nanoparticles such as the HAp/Col, and are working to publish ISO standard documents. Through these works, we are contributing to the development, practical application, and strengthening of Japan's international competitiveness in biomaterials.