Impact of sterilization by electron beam, gamma radiation and X-rays on electrospun poly-(ε-caprolactone) fiber mats

Biodegradable polymers such as polycaprolactone (PCL) are increasingly used for electrospinning substrates for tissue engineering. These materials offer great advantages such as biocompatibility and good mechanical properties. However, in order to be approved for human implantation they have to be sterilized. The impact of commonly used irradiation sterilization methods on electrospun PCL fiber mats was investigated systematically. Electron beam (β-irradiation), gamma and X-ray irradiation with two different doses (25 and 33 kGy) were investigated. To determine the impact on the fiber mats, mechanical, chemical, thermal properties and crystallinity were investigated. Irradiation resulted in a significant decrease in molecular weight. At the same time, crystallinity of fiber mats increased significantly. However, the mechanical properties did not change significantly upon irradiation, mostly likely because effects of a lower molecular weight were balanced with the higher degree of crystallinity. The irradiation effects were dose dependent, a higher irradiation dose led to stronger changes. Gamma irradiation seemed to be the least suited method, while electron beams (β irradiation) had a lower impact. Therefore, β irradiation is recommended as sterilization method for electrospun PCL fiber mats.