Scanning Electron Microscopic Study of In Vitro Toxicity of Ethylene Oxide Sterilized Bone Repair Materials.

Polylactic acid PLA and polyglycolic acid PGA have been under investigation for use in the management of hard and soft tissue wounds. Current research has included the incorporation of osteoinductive substances into a PLA-PGA copolymer allocplastic implant material for enhancing the healing of osseous defects. Conventional methods of sterilization such as dry heat, steam heat or cobalt 60 radiation, tend to either destroy or attenuate osteoinductive activity and alter polymer degradation. Ethylene oxide EO gas sterilization is currently being tested as an alternate method. This study examined the relationship of EO-induced cytotoxicity to the length of time of polymer aeration following EO sterilization. Three groups of copolymer implant discs were studied 1 5050 PLA-PGA copolymer, 2 PLA-PGA polymer with hydroxyapatite HA and 3 PLA-PGA with autolyzed, antigen--extracted AA bone particles. SEM examination revealed changes in cell growth with increasing periods of aeration suggestive of increasing cell vitality. Cells growing on discs having no aeration were small, round and lobulated whereas those of seven to fourteen days of aeration were more numerous, and flattened with many microvilli, pseydopodia, and dentritic processes, features consistent with normal cell morphology. These results suggest that EO sterilized polymer implants should be aerated at least seven to fourteen days prior to surgical use. aw