Osteoinductivity of Tunable Shape Memory Polymer-Bioglass Composite Scaffolds

Treatment of complex bone defects requires scaffolds that readily conformably fit to the contours of irregular defects while also providing the requisite mechanical properties, tailorable resorbability, and bioactivity. In this study, we investigated the osteogenic capacity of a family of shape memory polymer (SMP) composite scaffolds prepared as networks from acrylate-derivatized star- or linear-poly(ε-caprolactone) (PCL) or as semi-interpenetrating networks (semi-IPNs) with the inclusion of star- or linear-poly-l-lactic acid (PLLA). These networks were fabricated as porous composite scaffolds with up to 10 wt % 45S5 Bioglass (BG) localized to the pore walls using a solvent-casting particulate leaching process. In noncomposite scaffolds (i.e., 0 wt % BG), PCL/PLLA semi-IPNs demonstrated mixed effects on human bone marrow stem cell production of osteogenic proteins, depending on the linear or star architecture of the PCL and PLLA. Composite scaffolds with 10 wt % BG generally showed reduced levels of early osteogenic proteins, such as COL1A1, with the 10 wt % BG PCL/PLLA semi-IPNs also displaying marked increases in late-term osteogenic proteins, such as osteocalcin. These results suggest a potential trade-off between the beneficial effects of BG in terms of stimulating late-term osteogenesis and associated reductions in the deposition of the critical bone structural component COL1A1. Assessment of composite scaffolds with intermediate 5 wt % BG maintained the higher COL1A1 levels of 0 wt % BG scaffolds, while stimulating late-term ECM deposition and mineralization approaching those of the 10 wt % BG scaffolds.