Apatite Deposition on Hyaluronic Acid Gels in Biomimetic Conditions

Bioactive ceramics are used for bone-repairing owing to attractive features such as direct bone-bonding in living body, because they have the ability to bond directly to bone. However, there is limitation on clinical applications due to their inappropriate mechanical properties performances such as higher brittleness and lower fracture toughness than natural bone. Organic-inorganic hybrids consisting of organic polymer and the apatite would be attractive as novel bioactive bone substitutes with mechanical performances analogous to those of natural bone. We attempted preparation of apatite-polymer hybrids from hyaluronic acid. It has been attractive for bone- and cartilage-repairing materials due to high biological compatibility. The hydroxyl groups in side chains of the hyaluronic acid were bridged by divinylsulfone. Dense films were obtained after drying at ambient pressure, whereas porous specimens were formed by freeze-drying. They were treated with 1 M-CaCI2 aqueous solution for 24 h. Ability of apatite formation on the specimens was examined in vitro using simulated body fluid (SBF, Kokubo solution). The specimens formed the apatite in SBF within 7 d, when they were previously treated with CaCb solution