Preparation and Characterization of 3D-printed Lithium-doped Calcium Silicate Scaffold for Osteochondral Regeneration

Traditional treatment strategy for knee cartilage injuries (such as osteochondrosis dissecans, early degenerative arthritis, femoral condyle necrosis) includes mosaicplasty, which usually requires surgeons to harvest healthy cartilage tissues from other non-weight bearing joints. The development of surface modification techniques have brought a major paradigm shift for clinical bone tissue regeneration applications. In this study, we modified the surface of calcium silicate scaffolds (CS) with lithium ions (Li) via a simple immersion technique and evaluated its capabilities for bone regeneration. Li has been reported to have anti-inflammatory, osteogenic and chondrogenic capabilities via the promotion of several intracellular signalling pathways. Our results showed that Li ions could be easily coated onto the surfaces of CS scaffolds without affecting the microstructural properties of CS itself. In addition, the modifications did not affect printing capabilities of CS and porous scaffolds could be fabricated via the extrusion method. Furthermore, the presence of Li showed improvements in surface roughness and hydrophilicity, thus leading to enhanced secretion of osteochondral-related regeneration factors such as ALP, BSP and Col II proteins. Subsequent in vivo studies, including histological and micro-CT analysis confirmed that our Li-modified CS scaffolds were able to promote osteochondral regeneration. From our NGS analysis, the enhanced osteo-chondrogenic capabilities of our scaffolds were hypothesised to be influenced by paracrine exosomes. Taken together, we hoped that our study could inspire more osteochondral regeneration studies using the surface modification techniques.