How to sterilize biodegradable polymers? An in-depth characterization of effects of low energy electron beam irradiation (LEEI) and gamma irradiation on the molecular weight of poly(lactide-co-glycolide) films

Ionizing radiation is routinely used for sterilization of medical and biomedical products. The most commonly used radiation type for this purpose, gamma rays, features several drawbacks related to the high energy of the radiation, such as being restricted to dedicated external facilities. Low energy electron irradiation (LEEI) is an alternative type of irradiation, suitable for sterilization with significantly lower material penetration, allowing in-process implementation with smaller shielding, but also requiring more involved sample preparation. In this study, we investigated the effect of comparable doses of LEEI and gamma irradiation on the molecular weight distribution of thin films made from PLGA, a biodegradable polyester that is a biomaterial of interest for the design of medical devices and medicinal products such as microparticles for controlled drug release. For the study, the PLGA films were placed into sealed packaging with an inert helium atmosphere, and the effect of this packaging on LEEI absorption was calculated in order to correlate the measured dose under the package to the dose received by the sealed films. For both radiation types, irradiation resulted in a decrease of the PLGA molecular weight that became more pronounced at higher doses. Comparing low energy electrons and gamma rays, no significant differences were found in the characteristic parameters of the molecular weight distribution at the same dose range. Together, these results indicate that single product in-process sterilization by LEEI may be a suitable approach for medical devices and products from PLGA.