Bioactive, PDMS-containing shape memory composite scaffolds with accelerated degradation rates

A self-fitting scaffold could enable a regenerative engineering approach to treat irregular craniomaxillofacial (CMF) bone defects. We have previously reported conformally fitting, shape memory polymer (SMP) scaffolds based on poly(ε-caprolactone) (PCL). The fitting temperature (i.e., melt temperature, Tm) was tuned based on PCL architecture: linear-PCL-diacrylate (linear-PCL-DA; Tm = ∼55 °C) or star-PCL-tetraacrylate (star-PCL-TA, Tm = ∼45 °C). Scaffolds were also formed as semi-interpenetrating networks (semi-IPNs) by incorporating thermoplastic poly(L-lactic acid) (PLLA). The inclusion of a polydimethylsiloxane-dimethacrylate (PDMS-DMA) macromer and 45S5 Bioglass® (BG) were independently shown to promote hydroxyapatite (HAp) mineralization, as well as to accelerate degradation. In this study, PDMS-containing, composite SMP scaffolds were prepared with varying macromer compositions and BG concentrations. PCL/PDMS co-matrix scaffolds were formed with either linear-PCL-DA or star-PCL-TA, and PDMS-DMA (75:25 wt%). PCL/PLLA/PDMS (75:12.5:12.5 wt%) co-matrix-semi-IPNs were also formed. BG was included at relatively low concentrations (5 and 10 wt%). Composite scaffolds were fabricated to concentrate BG on the pore walls via a modified solvent-cast particulate leaching (SCPL) approach with a fused salt/BG template. PDMS-containing scaffolds preserved shape memory behavior and were non-brittle. In vitro degradation rates were accelerated for PDMS-containing composite scaffolds, owing to a combination of phase separation of polymer components and hydrophilicity imparted by the BG. Additionally, robust bioactivity was observed for PDMS-containing composite scaffolds with HAp mineralization commencing in just 1 day (1X simulated body fluid; SBF).