Formation of 4,4'-methylenedianiline in polyurethane potting materials by either gamma-ray or autoclave sterilization

In this experiment, we found that a potential carcinogen, 4,4'-methylenedianiline (MDA), was produced from gamma-ray irradiated potting materials, medical thermosetting polyurethane (PU). gamma-Ray irradiated PUs were immersed in either methanol or in equine serum. The time course of MDA leached from the potting materials and other variables were compared. A significant relationship was noted between the amount extracted and the rigidity of the potting material. The accumulated amount of extracted MDA (a few ppm in the original sample) increased with increasing irradiation dose by a second-order equation. One sample indicated reduced MDA elution after irradiation in the early stage. MDA extraction with serum was 82-87% that with methanol. In one case, MDA leaching into serum in the early stage was higher than that into methanol. Autoclave sterilization did not promote MDA formation, thus indicating that autoclaving would be preferable.