Effects of gamma irradiation on osteoinduction associated with demineralized bone matrix

Gamma irradiation is frequently used to sterilize implanted devices but has limitations when used on biologically active materials and composites. In this study, we have evaluated the changes of biological activity of demineralized bone matrix (DBM) in the dry state and in the presence of aqueous and non-aqueous carriers while exposed to various levels of ionizing radiation. The activity of DBM in the dry state remains relatively stable with only a small loss of activity. Composites of DBM with a carrier such as lecithin, to which no water has been added, lose activity at approximately the same rate as DBM in the anhydrous form. In composites that contain water, the loss of activity occurs even at much lower levels of radiation exposure. Gamma irradiation does not change cell attachment to the DBM matrix but has an influence on both stem cell and osteoprecursor cell proliferation rates. Because of the limitations imposed by radiation, it seems most practical to handle DBM aseptically throughout the procedures of compositing pastes, putties, or suspensions, and only if necessary exposing the inert excipients to radiation sterilization prior to mixing.