Influence of Sterilization Regime on Mechanical Properties of Calcium Carbonate-Reinforced Polycaprolactone Scaffolds for Bone Regeneration.

Abstract

Sterilization is of utmost importance for the clinical application of biomaterials. Here, we present our findings on the influence of various sterilization regimes on the mechanical properties and the degradation of calcium carbonate reinforced polycaprolactone (PCL), a commonly used biomaterial for example, for bone substitution. Furthermore, studies on the impact of additives' specific surface were included. It was shown that both gamma and electron beam sterilization with direct and pulsed application of 25 kGy radiation resulted in a decrease of M_N and an increase of M_W, corresponding to the occurrence of chain scission and branching reactions, respectively. Here, pulsation and the use of gamma rays were shown to decrease the impact of sterilization on molecular weight. Overall, sterilization resulted in an increase of Young's moduli in bulk specimens. Identical observations were made regarding an increase in specific additive surface area. In 3D-printed scaffolds, however, no influence of sterilization regime or additive surface area on the mechanical properties was observed. During degradation (hydrolysis), chain scission and branching reactions have contrary effects regarding degradation velocity. Therefore, gamma-sterilized specimens showed no effect, which was attributed to an offset of the effects of both modifications. Electron beam sterilization, however, inhibited degradation due to increased PCL branching reactions. This effect could be circumvented by additives with high specific surface, which showed reduced particle-matrix interaction after electron beam sterilization, attributed to the generation of characteristic high-energy X-ray radiation and radicals in close proximity to calcium carbonate particles.