Effects of gamma-irradiation, storage and hydration on osteoinductivity of DBM and DBM/AM composite

This study investigated the effect of gamma-irradiation dose, irradiation temperature, hydration and storage condition on osteoinductivity of demineralized bone matrix (DBM) and demineralized bone matrix/acellular dermal matrix (DBM/AM) composite. DBM and DBM/AM in dry and hydrated form were treated with gamma-irradiation of 15-40 kGy at ambient or low temperature (-40 degrees C approximately -70 degrees C) and then stored at ambient condition for 6 months. The athymic rat muscle implant model was used to evaluate the osteoinductive potential of the DBM and DBM/AM composites. Histological and alkaline phosphatase (ALPase) activity assessments were carried out at 28 days after implantation to determine the new bone formation and ALPase activity. Both histological and ALPase activity analysis showed that the osteoinductivity of DBM decreased with the increase of gamma-irradiation dose at ambient temperature, whereas no decrease occurred when treated with gamma-irradiation at low temperature. However, the hydrated DBM showed diminishing osteoinductivity after 6-month storage at ambient condition, whereas the DBM in dry form retained their osteoinductivity after the 6-months storage. The findings in this study indicate that DBM and DBM/AM composites could retain their osteoinductivity when they are in dry configuration and are irradiated at low temperature (-40 degrees C approximately -70 degrees C) using the custom-made cold gamma-irradiation system.