The effect of gammairradiation for collagen in demineralized bone matrix particles with differences size

Objective To investigate the effects of different particle sizes on the collagen structure of demineralized bone matrix (DBM) and the effectiveness of dry ice as an irradiation protectant in the procedure of gamma irradiation. Methods DBM samples with different particle sizes (0.5-1.0 mm, 1.2-2.8 mm, 3.3-4.7 mm and 5.7-7.0 mm) were prepared, and sterilized with several doses of gamma irradiation (0 kGy, 15 kGy and 25 kGy) at room temperature. Additionally, another group of DBM samples were sterilized with 25 kGy gamma irradiation with protective agent. Changes in surface and characteristics of collagen were observed by using scanning electron microscope (SEM), Sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE), differential scanning calorimetry (DSC) and carbonyl content. Results The color of collagen extract indicated that oxidative damage is directly related to irradiation dose. SEM showed that the gamma irradiation caused collagen structure disorder and fiber breakage. As the irradiation doses increased, the damage area significantly increased. When the particle size increased, the damage area tended to decrease. The DSC showed that the thermal denaturation temperature of 5.7-7 mm, 3.3-4.7 mm, 1.2-2.8 mm and 0.5-1.0 mm were 142.8℃, 97.3℃,84.3℃ and 83.9℃, respectively. The differences of the thermal denaturation temperatures among the four particle sizes were statistically significant (F=0.560, P=0.650). Collagen structure was destroyed by gamma irradiation, resulting in a decrease in collagen molecular weight. While, large particle DBM had a tendency to resist radiation damage. There was a significant difference on the contents of carbonyl in collagen from same particle sizes of DBM with different irradiation dose. The carbonyl content gradually decreased with the increase of particle size, but the difference was not statistically significant (F=0.560, P=0.650). Conclusion The gamma irradiation and collagen oxidative damage have obvious dose-response relationship. With the increase of gamma irradiation dose, the degree of collagen damage increases. The sizes of DBM could affect the sensitivity of collagen to gamma irradiation. With the decrease of particle sizes, DBM particles are more susceptible to gamma irradiation damage. Additionally, dry ice, as a radiation protection agent, has a certain degree protection effect against radiation. Key words: Bone matrix; Collagen; Radiation; Gamma rays