Effects of Gamma Sterilization on the Mechanical Behavior and Degradation of Polylactic Acid (PLA) in Biomedical Applications

Thermoplastic polymers are widely used in medical devices because they provide a favorable balance of mechanical performance, manufacturability, biocompatibility, and cost efficiency. Among these materials, polylactic acid (PLA) has become one of the most relevant biodegradable polymers for biomedical applications due to its biocompatibility, processability, and ability to degrade through hydrolytic cleavage of ester bonds [7]. However, PLA-based devices intended for clinical use must undergo sterilization, and gamma irradiation is commonly used for its high penetration and effectiveness in complex geometries. This work presents a qualitative literature review on the effects of gamma sterilization on the physicochemical, mechanical, and degradation behavior of PLA in biomedical applications, supported by a literature-based theoretical finite element analysis (FEA) model using an ASTM D638-style tensile specimen. The reviewed literature indicates that gamma irradiation, commonly applied at sterilization doses around 25 kGy and evaluated in higher-dose or repeated-exposure conditions, can induce significant physicochemical changes in PLA. These changes are mainly associated with free radical formation and chain scission, resulting in reduced molecular weight, changes in crystallinity, reduced elongation at break, decreased tensile performance, and increased brittleness [1], [10], [11], [15]. Theoretical FEA comparisons of non-sterilized, gamma-sterilized, and double-sterilized PLA further illustrated that sterilized conditions may exhibit reduced structural margin under identical tensile loading conditions due to lower yield strength, lower tensile strength, and reduced strain tolerance. Overall, the findings show that gamma sterilization should be treated not only as a final sterility assurance process but also as a material-modifying factor that can affect the mechanical reliability and the predictability of degradation in PLA-based biomedical devices. Therefore, sterilization parameters should be integrated into early-stage biomaterial selection, design verification, and validation planning to ensure the safety, functionality, and long-term performance of PLA-based medical devices.