(387b) Strengthening Interfacial Mechanics through Biomimetic Interdigitations in CG-Cgcap Scaffolds for Tendon-Bone Regeneration

The tendon bone junction (TBJ) is a highly specialized tissue which transmits high tensile loads from tendon to bone. Physical stresses are concentrated across the TBJ interface, and a healthy TBJ can dissipate these stress concentrations without failure. However, the TBJ is a common injury site which displays poor healing properties.  Current surgical techniques do not provide regeneration at the TBJ and the re-failure rate is extremely high (>90%), due to scar tissue replacing the highly specialized tissue at this junction. To improve the regenerative function of the TBJ, it is therefore necessary to enhance its mechanical properties. We are developing a collagen-glycosaminoglycan (CG) scaffold which mimics elements of the biophysical heterogeneities of the native TBJ in vitro. For improved tensile competence, we utilized biomimetic geometries inspired by the plates of turtle shells and armored fish to create an interface between distinct non-mineralized (CG) and mineralized (CGCaP) compartments in a single CG-CGCaP scaffold. CG-CGCaP scaffolds were created by lyophilizing a suspension of type I collagen and chondroitin sulfate. Interdigitated interfaces in scaffolds were created by placing a toothed divider in the mold with mineralized slurry on one side and non-mineralized slurry on the other, with the divider removed shortly before lyophilization. Scaffolds were characterized via Scanning Electron Microscope (SEM), microcomputer tomography (μCT), and mechanical tensile testing with digital image correlation (DIC). SEM confirmed that the mineral content was localized within the toothed geometry of the mineral compartment. The interfacial mechanical strength, dictated by the degree of interdigitation between scaffold compartments, was found to depend on two parameters: the angle, and therefore number, of teeth across the interface of each sample. Thus, more interfacial area is created and the interfacial strength is expected to increase. As expected, tensile tests showed that failure load and elastic modulus increased with increasing interdigitation, and failure mode also varied between interfacial geometries. Ongoing effors are using DIC to reveal lower stress concentrations at more highly interdigitated interfaces. Overall, we have shown that an interdigitated scaffold interface can increase the mechanical competence of the interface within a multicompartment CG-CGCaP scaffold for TBJ regeneration applications.