Event Abstract Back to Event Real time 3D in situ assessments for bone tissue engineering Natalie Reznikov1, 2, 3, Spencer W. Crowder1, 2, 3, Mads S. Bergholt1, 2, 3 and Molly M. Stevens1, 2, 3 1 Imperial College London, Department of Materials, United Kingdom 2 Imperial College London, Department of Bioengineering, United Kingdom 3 Imperial College London, Institute of Biomedical Engineering, United Kingdom Introduction: Porous 3D scaffolds are of great interest to the bone tissue engineering field[1],[2]. Their high surface-to-bulk ratio provides a niche for osseointegration. Moreover, the natural organization of trabecular bone tissue normally present in vertebrae and in articular ends of long bones is an open-cell solid that provides appropriate compliance and shock-absorbing properties in skeletal biomechanics. As was recently shown in a multi-scale study of organization of trabecular bone[3], the micrometer-scale alignment of collagen fibrils and the millimeter-scale 3D architecture of trabecular struts are complementary. This complementarity is seen by the orientation of collagen fibrils in a trabecula either following the axis of their own strut or aligned with the axis of a contiguous strut. This organization of the bone extracellular matrix as secreted and assembled by mechano-sensing osteoblasts is dependent upon cell responsiveness to substrate stiffness, composition and geometry. As a result of this outside-in signaling to the cells, extracellular matrix assembly and organization ‒ whether on a natural or artificial surface ‒ depends on the material properties of the substrate, including its 3D architecture. Materials and Methods: We are developing a biomimetic, non-resorbable 3D-printed scaffold to be used as prosthetic material for total joint replacement. The biomimetic scaffold is a repetitive lattice, the symmetry of which is close to the mathematically simplified fabric of trabecular bone. The 3D architecture of its structural members contributes to the nature-like shock-absorbing properties of the scaffold. The scaffold is fabricated of polyamide using selective-laser sintering, a method of additive manufacturing where powder substrate is consolidated by laser pulses, thus allowing to produce intricate architecture with high precision. The high topographic complexity of sintered polyamide allows for post-fabrication deposition of bioactive compounds such as bioactive glass directly on its surface via sol-gel route. Results and Discussion: We have compared the following two parameters of the scaffold ‒ the surface composition and its geometry ‒ using osteogenic cell cultures. The effect of surface composition on osteogenic culture progression was compared between pure polyamide substrate and polyamide having incorporated bioactive glass. The effect of different topological motifs of the 3D shock-absorbing scaffold on geometry-driven osteoblast culture development was assessed by culture evaluation on 3D scaffold fragments with acute, right and obtuse angles. The cell-instructive properties of the scaffold geometry and composition were continuously monitored using in situ live-cell Raman micro-spectroscopy - a method of non-destructive profiling of molecular moieties and monitoring of cell culture dynamics[4]. Preliminary results confirm the benefits of high substrate curvature for deposition of the extracellular matrix, and the high osteogenic potential of bioactive glass. Conclusions: The observation of substrate geometry and composition effects of an osteogenic cell culture offers feasible strategies to integrate compositional and topological osteogenic factors into a 3D scaffold for bone regeneration.
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