CRIS -Creative Research Institution- Hokkaido University

【Division of Frontier Research】Junzo TANAKA

Junzo TANAKA Life Science
Learn from living body and regenerate tissues -Nanobiotechnology toward highly advanced medical society-
Junzo TANAKAProfessor

Division of Frontier Research: Life Science

Living tissues have higher hierarchical structures composed of individual molecules and have requisite functions to live on the Earth. For example, procollagen is produced in endoplasm and released, and forms collagen fibers by self-organization. The self-organized materials are considered as very important for the expression of active and passive functions of higher hierarchical structures, i.e., extracellular matrices, in vivo. Therefore, the reconstruction of the higher hierarchical structures should be a very important factor for producing highly functional biomaterials. However, the self-organization of the materials is generated by a greatly complicated process. In consequence, it is very important for the reconstruction of biomimetic structures to understandan interfacial interaction between materials such as ions, the coordination of molecules, hydrogen bonding, etc., and to applyi it to material design.

 

Fish scale to cornea

Fish scale is composed of Ca-deficient apatite and organic materials (mainly type-I collagen). The scale has an orthogonal plywood structure of stratified lamellae in the internal layer; the collagen fibers are co-aligned within each sheet, which rotates alternately through an angle of 90 degree. Such kind of high hierarchical structure is formed by the interaction between substances at the outside of cells, which is called self-organization phenomenon. Particularly, the mineralization occurs in the internal layer, and the c-axis of apatite crystals are aligned along the collagen fibers. It is speculated that the chemical interfacial interaction between apatite and collagen also affects the creation of the hierarchical structure. Using the self-organization phenomenon of apatite and collagen could reconstruct the three-dimensional structure that is very similar to fish scale. The hierarchical structure created will be applicable for the tissue engineering of artificial cornea.

 

Crab tendon to ligament

Crab shells and tendon are mainly composed of chitin, one of glycosaminoglycans. The chitin in the shells has no oriented structure but it in the tendon is oriented to one-axis direction. Further, an inorganic substance in the shells is calcium carbonate as same as the clamshells, but it in the tendon is apatite as same as our bone. Therefore, the self-organization of apatite and chitin should be important in the oriented structure of the tendon. The oriented structure is strong to tensile strength parallel to the oriented direction and can be useful for human ligament regeneration materials. However, the crab tendon is too short to apply clinically, and the structure must be reconstructed artificially. We will try to reconstruct the ordered structure with high strength by use of self-organization between apatite and chitosan, the latter is a chitin derivative with high-bioaffinity, and apply to artificial ligaments.