Effect of different γ-irradiation doses on cytotoxicity and material properties of porous polyether-urethane polymer

Biomaterials respond to sterilization methods differently. Steam sterilization might decrease the performance of thermoplastic polyether‐urethane (TPU); however, the effect of different γ‐radiation doses on this polymer is contradictory in present literature. The purpose of this study was to investigate the differences between irradiative doses in comparison with steam sterilization on a porous TPU scaffold produced by a new processing method. No significant differences in the surface chemical structure were found with attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) analysis when comparing with the sterilization methods. The molecular weight (Mw) had a net increase from 11.5 ± 0.039 to 13.2 ± 0.072 kDa by γ‐sterilization from 10 to 60 kGy. The samples that were irradiated (>60 kGy) had also an increase in polydispersity index (PDI; 1.45 ± 0.007) in comparison with the nonsterile ones (1.31 ± 0.017), which indicate branching. Liquid chromatography/mass spectroscopy (LC/MS) analysis showed that there was a correlation between the concentration of the breakdown product, methyl dianiline, and cytotoxicity. The concentration of this compound was found to be four times higher in steam‐sterilized sample (1.3 ± 0.01 ppb) compared with that of the polymer sample γ‐sterilized at 10 kGy (0.3 ± 0.01 ppb). The cytotoxicity of TPU was found to decrease with higher radiation doses, and was significantly higher for the steam‐sterilized samples. It is recommended that TPU produced with the described foaming method should be sterilized by γ‐irradiation at 25 kGy or higher doses. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007