Biodegradable poly(ε-caprolactone)/poly(silyl fumarate) shape memory scaffolds

Biodegradable shape memory scaffolds have the unique potential to heal irregularly shaped craniomaxillofacial (CMF) defects through conformal 'self-fitting'. These have been previously prepared from poly(ε-caprolactone) diacrylate (PCL-DA), but the slow biodegradation rate of PCL is expected to limit neotissue formation. Subsequently, telechelic siloxane macromers polydimethylsiloxane-dimethacrylate (PDMS-DMA) and polymethylhydrosiloxane-DMA (PMHS-DMA) were combined with PCL-DA at varying weight (wt)% ratios, resulting in PCL/PDMS and PCL/PMHS co-network scaffolds with accelerated degradation rates owing to phase separation that increased water uptake. Still, these siloxane macromers lack a hydrolytically unstable backbone thus limiting degradation. Herein, poly(silyl fumarate) (PSF) was synthesized as a hybrid siloxane macromer with a hydrolytically unstable backbone as well as interchain crosslinkability. PCL/PSF scaffolds were prepared at 90:10, 75:25, 60:40, and 50:50 wt% of PCL-DA to PSF via solvent-casting particulate leaching (SCPL) with a fused salt template. Despite a reduction in PCL crystallinity (i.e., switching segments) with 40 and 50 wt% PSF, all scaffolds maintained excellent shape memory behavior. PCL/PSF scaffolds with 10 and 25 wt% PSF also maintained the modulus of the PCL-only scaffold as well as the corresponding PCL/PDMS and PCL/PMHS scaffolds. In vitro degradation under basic conditions revealed that PCL/PSF scaffolds with just 10 wt% PSF degraded faster than the PCL-only scaffold and further increased with 25 wt% PSF to surpass that of the corresponding PCL/PDMS scaffold. A lack of phases separation was observed, and thus indicated that faster degradation was achieved by the hydrolytic instability of the PSF.