A collagen-based bilayer nanocomposite scaffold for osteochondral tissue regeneration: integrating hydroxyapatite and cellulose nanocrystals

Regenerating osteochondral (OC) defects remains a significant challenge in regenerative medicine due to the complex nature of these tissues and their limited self-healing capacity. While tissue engineering offers a promising solution, developing a comprehensive, long-term regenerative strategy is still an active area of research. This study focused on fabricating of a biocompatible bilayer collagen (COL) based scaffold, designed with a bone layer containing hydroxyapatite (HAp) nanoparticles and a cartilage layer incorporating cellulose nanocrystals (CNCs) and hyaluronic acid (HA). Fabricated through COL fibrillation and gelation subsequent with plastic compression and freeze-drying, the scaffold provided proper environment for both bone and cartilage cells. The inclusion of HAp and CNCs not only enhanced the mechanical properties of the scaffolds but also provided structural similarity to the native matrix of these tissues, thereby improving bioactivity. The bone layer, featuring larger pores, structurally resembled hard bone tissue and supported excellent survival, adhesion, and proliferation of MG-63 cells (a human osteoblastic cell line). In contrast, the cartilage layer, provided a hydrated, bioactive environment similar to natural cartilage with smaller, well-distributed pores that promoted the adhesion and growth of C28/I2 chondrocytes (an immortalized human chondrocyte line). Together, these properties enhance the scaffold's capacity for effective OC tissue regeneration. These findings highlight the scaffold's potential for effective OC tissue regeneration, offering a promising step forward in tissue engineering and regenerative medicine.