Impact of Sterilization Method on Protein Aggregation and Particle Formation in Polymer-Based Syringes

The effects of sterilization methods on the storage stability of erythropoietin (EPO) in polymer-based syringes were assessed by quantifying protein oxidation, aggregation, and particle formation. Micro-particle counting and size exclusion chromatography coupled with a multi-angle light scattering detector demonstrated much lower levels of protein particles and aggregates for EPO stored for 12 weeks in steam-sterilized than in radiation (Rad)-sterilized syringes. Intermediate levels of damage were observed for EPO stored in ethylene oxide-sterilized syringes. HPLC analysis documented that the Rad-sterilized syringes caused increased oxidation of the protein during storage. In contrast, in the steam- and ethylene oxide-sterilized syringes EPO oxidation did not change. Analysis with electron spin resonance revealed that only Rad-sterilized syringes formed radicals in the syringe body, which persisted over the 12-week storage period. These results demonstrated that Rad-sterilization generated radicals in the syringes which in turn caused increased EPO oxidation, particle formation, and protein aggregation. Therefore, steam sterilization was shown to be a preferable sterilization method for the polymer-based syringe system when using biopharmaceutical drugs highly sensitive to oxidation, and particle formation and aggregation.