![]() ![]() Material-driven approaches to confer bioactivity have generally relied on inorganic, hydrophobic silicon- and calcium phosphate-containing fillers (e.g., bioglasses, nanosilicates, β-tricalcium phosphates, and HAp). Thus, an approach that would render innate bioactivity throughout PCL-based SMP scaffolds would improve the regenerative potential. 13, 23 However, application of the polydopamine coating requires additional fabrication steps and the coating is largely lost as the scaffold begins to erode. Thus, tens of nanometer (nm)-thick bioactive polydopamine coating were applied to PCL-DA scaffolds and shown to promote mineralization as well as mesenchymal stem cell (MSC) osteogenesis. 19– 22 In this regard, the lack of innate bioactivity of PCL-DA and PCL-DA/PLLA SMP scaffolds limits their regenerative potential. Thus, the scaffold should also be bioactive, inducing the formation of a carbonated hydroxyapatite (HAp) at the surface for bonding to the adjacent bone. 17, 18 In a material-guided approach to regeneration, scaffold properties alone (i.e., without exogenous growth factors) elicit bone formation. 14– 16 Moreover, increased rates of biodegradation and mechanical strength were achieved with a semi-interpenetrating network (semi-IPN) designs based on PCL-DA and thermoplastic poly( l-lactic acid) (PLLA). Fabrication with a fused salt template produced SMP scaffolds with pore sizes in the range known to promote osteogenesis (~200 to ~350 μm) and pore interconnectivity necessary for neotissue infiltration. ![]() Upon exposure to warm air or saline (~55 ☌), the porous PCL-DA scaffolds become malleable such that they can be press-fit into irregular geometries, with shape-recovery driving its expansion to fill the defect and shape fixity locking it into its new shape. 13 Based on biodegradable poly( ε-caprolactone)diacrylate (PCL-DA), the crystalline lamellae ( T m or “ T trans” ~55 ☌) serve as the switching segments while the netpoints are formed by cross-links. 9– 12 We have previously proposed thermoresponsive shape-memory polymers (SMPs) as self-fitting scaffolds for the repair of irregular bone defects. 6– 8 Shape-memory polymers (SMPs) have received attention for their use in a variety of medical device applications. In situ forming synthetic scaffolds suffer from brittle mechanical properties, inadequate porosity, exothermic cures, and post-cure shrinkage leading to poor tissue contact. 1– 5 Regenerative engineering is a promising approach, but it requires a scaffold that could readily achieve a conformal fit within irregular defects. While autografting remains the gold standard, difficulty in shaping and positioning the rigid graft frequently leads to a lack of good contact to adjacent tissues and subsequent graft resorption. 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.Ĭraniomaxillofacial (CMF) bone defects present a unique challenge for repair due to irregular geometries. Irrespective of PDMS content, all PCL/PDMS scaffolds exhibited the formation of carbonated hydroxyapatite (HAp) following exposure to simulated body fluid (SBF). Degradation rates increased with PDMS content and reduced cross-link density, with phase separation contributing to this effect. Scaffolds exhibited pore interconnectivity and uniform pore sizes and further maintained excellent shape-memory behavior. ![]() Additionally, a triblock macromer (AcO-PCL 45- b-PDMS 66- b-PCL 45-OAc), having a 65:35 wt % ratio PCL/PDMS, was used. Specifically, PCL 90-DA was combined with linear-PDMS 66-dimethacrylate (DMA) or 4-armed star-PDMS 66-tetramethacrylate (TMA) macromers at 90:10, 75:25, and 60:40 wt % ratios. These were prepared as co-matrices with three types of macromers to systematically alter PDMS content and cross-link density. Thus, this work reports the introduction of PDMS segments to form PCL/PDMS SMP scaffolds. Polydimethylsiloxane (PDMS) has been shown to impart innate bioactivity and modify degradation rates when combined with organic cross-linked networks. However, PCL-DA scaffolds lack innate bioactivity and degrade very slowly. 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. 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. ![]()
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