A material-guided, regenerative approach
to heal cranial defects
requires a scaffold that cannot only achieve conformal fit into irregular
geometries but also has bioactivity and suitable resorption rates.
We have previously reported “self-fitting” shape-memory
polymer (SMP) scaffolds based on poly(ε-caprolactone) diacrylate
(PCL-DA) that shape recover to fill irregular defect geometries. However,
PCL-DA scaffolds lack innate bioactivity and degrade very slowly.
Polydimethylsiloxane (PDMS) has been shown to impart innate bioactivity
and modify degradation rates when combined with organic cross-linked
networks. Thus, this work reports the introduction of PDMS segments
to form PCL/PDMS SMP scaffolds. These were prepared as co-matrices
with three types of macromers to systematically alter PDMS content
and cross-link density. Specifically, PCL90-DA was combined
with linear-PDMS66-dimethacrylate (DMA)
or 4-armed star-PDMS66-tetramethacrylate
(TMA) macromers at 90:10, 75:25, and 60:40 wt % ratios. Additionally,
a triblock macromer (AcO-PCL45-b-PDMS66-b-PCL45-OAc), having a 65:35
wt % ratio PCL/PDMS, was used. Scaffolds exhibited pore interconnectivity
and uniform pore sizes and further maintained excellent shape-memory
behavior. Degradation rates increased with PDMS content and reduced
cross-link density, with phase separation contributing to this effect.
Irrespective of PDMS content, all PCL/PDMS scaffolds exhibited the
formation of carbonated hydroxyapatite (HAp) following exposure to
simulated body fluid (SBF). While inclusion of PDMS expectedly reduced
scaffold modulus and strength, mineralization increased these properties
and, in some cases, to values exceeding or similar to the PCL-DA,
which did not mineralize.
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