Mechanical and Physical Characterization of a Biphasic 3D Printed Silk-Infilled Scaffold for Osteochondral Tissue Engineering

Osteochondral tissue damage is a serious concern, with even minor cartilage damage dramatically increasing an individual's risk of osteoarthritis. Therefore, there is a need for an early intervention for osteochondral tissue regeneration. 3D printing is an exciting method for developing novel scaffolds, especially for creating biological scaffolds for osteochondral tissue engineering. However, many 3D printing techniques rely on creating a lattice structure, which often demonstrates poor cell bridging between filaments due to its large pore size, reducing regenerative speed and capacity. To tackle this issue, a novel biphasic scaffold was developed by a combination of 3D printed poly(ethylene glycol)-terephthalate-poly(butylene-terephthalate) (PEGT/PBT) lattice infilled with a porous silk scaffold (derived from <i>Bombyx mori</i> silk fibroin) to make up a bone phase, which continued to a seamless silk top layer, representing a cartilage phase. Compression testing showed scaffolds had Young's modulus, ultimate compressive strength, and fatigue resistance that would allow for their theoretical survival during implantation and joint articulation without stress-shielding mechanosensitive cells. Fluorescent microscopy showed biphasic scaffolds could support the attachment and spreading of human mesenchymal stem cells from bone marrow (hMSC-BM). These promising results highlight the potential utilization of this novel scaffold for osteochondral tissue regeneration as well as highlighting the potential of infilling silk materials within 3D printed scaffolds to further increase their versatility.