Abstract QS19: 3D-Printed Hyperelastic Bone in a Rat Critical Sized Calvarial Defect

PURPOSE: Bone substitutes have many applications in craniofacial surgery, yet current biomaterials remain limited. Hyperelastic bone (HB) is a composite of familiar materials, hydroxyapatite and poly-co-glycolide, with fundamentally unique physical and biocompatibility properties conferred by 3D-printing. Previously shown to induce osteogenic differentiation in vitro, this study aimed to characterize the osteoregenerative capacity of HB in a rat critical sized calvarial defect. METHODS: Hyperelastic bone scaffolds comprised of 90%vol hydroxyapatite and 10%vol PLG and porous “fluffy” PLGA (f-PLGA) scaffolds were fabricated by direct ink writing (200-micron nozzle, 250-micron spacing, 120-degree offset). The 8-mm diameter by 0.6-mm scaffolds were implanted into 8-mm diameter critical sized calvarial defects in rats. Controls included an empty defect and replacement of the autologous bone disc. The animals were sacrificed with Microfil infusion at 8 and 12 weeks postoperatively. Skulls were analyzed by histology and micro-computed tomography (micro-CT). RESULTS: Negative controls showed incomplete healing at 8 and 12 weeks. Positive autologous bone controls showed interdigitating bone processes at defect margins at 8 and 12 weeks. Hydroxyapatite-free f-PLGA scaffolds healed primarily with fibrous tissue and membranous cellular components within the scaffold at both timepoints. HB scaffolds contained fibrous tissue and membranous cellular components within the scaffold at 8 weeks and new bone formation at the defect margins at 12 weeks. Mineralized bone matrix was visualized by micro-CT. CONCLUSION: HB is capable of inducing bone formation in vivo in rats without the addition of exogenous growth factors or cells. 3D-printed hyperelastic bone has the potential to be a customizable, inexpensive, osteoconductive bone substitute. S.W. Jordan: None. Y. Huang: None. A.E. Jakus:; Co-founder; Dimension Inx, LLC. L. Zhao: None. R.N. Shah:; Co-founder; Dimension Inx, LLC. P.K. Patel: None.