Chitosan Enhances Osteogenetic Potential of Ethylene-Oxide Sterilized Demineralized Bone Matrix

Background: Demineralized bone matrix is used clinically to stimulate bone repair in orthopedics and dentistry. Demineralized bone matrix has osteoconductive and osteoinductive properties that contribute to its efficacy in new bone formation. However, ethylene-oxide sterilization in the clinical setting diminishes this efficacy. Studies using intramuscular implantation of demineralized bone matrix in rats demonstrate deterioration of its osteoconductive properties by ethylene oxide sterilization. Objective: The goal of this study is to investigate whether treatment with chitosan which is osteoconductive will improve the osteoconductivity of ethylene-oxide sterilized demineralized bone matrix and thus restore the original osteogenetic efficacy of demineralized bone matrix. Methods: We implanted normal and modified demineralized bone matrix implants into the abdominal muscles of Sprague-Dawley rats. New bone growth in implants, harvested at 4 weeks, was determined by mineral content, bone alkaline phosphatase activity, and histology. Results: The unmodified demineralized bone matrix implants demonstrated extensive areas of trabecular bone containing osteoblasts and osteocytes. Ethylene-oxide sterilization of demineralized bone matrix resulted in fibrosis, rather than new bone formation, in the intramuscular implantation site in the rat. Treatment of ethylene-oxide sterilized demineralized bone matrix with chitosan restored mineral content and bone alkaline phosphatase activity of these samples to control levels. Conclusion: Treatment of ethylene-oxide sterilized demineralized bone matrix with chitosan restores the osteoconductive properties completely so that new bone formation is comparable to that of nonsterilized demineralized bone matrix. Thus chitosan treatment of ethylene-oxide sterilized demineralized bone matrix may be used to restore the clinical efficacy of demineralized bone matrix after sterilization.