Impact of E-Beam Sterilization on Bioglass Composite Shape Memory Scaffolds

A "self-fitting" bioactive composite scaffold based on a shape memory polymer (SMP) and 45S5 Bioglass (BG) offers a promising regenerative treatment for irregularly shaped craniomaxillofacial (CMF) bone defects. Self-fitting is afforded by scaffolds prepared as crosslinked networks from linear-poly(ε-caprolactone)-diacrylate (linear-PCL-DA), and as semi-interpenetrating networks (semi-IPNs) with the inclusion of thermoplastic linear-poly(L-lactic acid) (linear-PLLA) (75:25 wt.%). Composites may be formed by inclusion of bioactive BG (5 and 10 wt.%) to elicit hydroxyapatite (HAp) mineralization and to increase degradation rates. To advance their clinical translation, such scaffolds must be conducive to modern sterilization methods. Electron beam (E-beam) sterilization is an attractive alternative to conventional methods (e.g., ethylene oxide). Herein, the effect of E-beam sterilization (25 kGy) on SMP composite scaffolds and non-composite controls was systematically assessed. Sterilized scaffolds largely preserved the PCL crosslinked network (i.e., similar sol contents) as well as pore features. The compressive mechanical behavior of sterilized scaffolds was also largely maintained. E-beam sterilization caused minor changes in PCL crystallinity, but excellent shape memory behavior was retained. In vitro degradation was somewhat faster following sterilization for scaffolds containing 10 wt.% BG. All E-beam sterilized composite scaffolds retained bioactivity, exhibiting HAp mineralization with exposure to simulated body fluid (SBF, 1X).