SYNOPSIS
The composite scaffold based on a mixture of DNA-chitosan complexes and carbon-ate apatite particles (DNA-chitosan-apatite complexes) was implanted into cranial bone of rats to evaluate an ability of the bone regeneration. By immersing the DNA-chitosan-apatite complexes disks in simulated body fluid (HBSS) for 3 days, precipitate formation on the disks was observed. Although the precipitates were scattered over the surface of the both DNA-chitosan-apatite complexes and DNA-chitosan complexes disks, early formation of precipitate clusters was observed for the DNA-chitosan-apatite complexes. For the XRD patterns of the DNA-chitosan-apatite complexes after 3 days-immersion in HBSS, the same spectrum for carbonate apatite alone were observed. The implanted DNA-chitosan-apatite complexes disks were gradually fragmentized into small pieces 7 weeks after surgery. Although numerous osteocyte-like cells were observed in these small pieces, the remaining of the carbonate apatite particles could not find in the implanted material. On 12 weeks, the implanted portion was totally replaced by newly generated bone tissues. In contrast, DNA-chitosan complexes disk was capsulated by fibrous connective tissue. No bone formation was observed in the implanted area in the tissue sections examined. It appeared that DNA-chitosan-apatite complexes have a good potential for bone response. The results of this study suggested that degradability of carbonate apatite would play an important role in process of bone generation.

Key words: bone response, carbonate apatite, DNA, chitosan complex