Assessment of Degradation for Porous PCL-PLLA Semi-IPN Shape Memory Polymer (SMP) Implants for Cranial Defect Repair

Within cranial bone defect treatments, autografts remain the current gold standard for best healing outcomes. However, if the defect is of a unique shape, this process proves difficult and often requires additional surgeries. The work herein focuses on a regenerative approach utilizing a shape memory polymer (SMP) scaffold that can "self-fit" into a defect while maintaining important properties for healing (e.g. osteoconductivity, robustness, degradability). Poly(ε-caprolactone) (PCL) is an extensively studied SMP but, alone, is limited in bone repair due to its relatively low modulus and slow degradation rate for adequate bone healing.[1-3] To improve these properties, our group reported SMPs comprised of a semi-interpenetrating network (semi-IPN) of cross-linked PCL diacrylate (PCL-DA) and poly(L-lactic acid) (PLLA), which have shown great potential.[4, 5] Here, we investigated the degradation behavior of porous PCL-PLLA semi-IPN SMP implants in vitro under both accelerated conditions and non-accelerated conditions towards ultimately predicting in vivo performance. Rapid degradation with greater PLLA wt% content was observed, along with mass losses up to ~9% at 5 months real-time degradation. Additionally, degradation was unaffected by the compressed implant "fitting" process, yet slightly accelerated by the application of a bioactive surface coating