Osteochondral defects caused by trauma or disease contribute to joint instability, ultimately leading to osteoarthritis. Therapies such as autologous transplantation and microfracture offer potential for osteochondral repair, but limitations remain, including donor shortages, infection risks, and immune rejection. Recent advances in tissue engineering and novel biomaterials have led to promising possibilities for osteochondral scaffolds. Notably, the osteochondral unit consists of the articular cartilage layer and the underlying subchondral bone layer, and the development of novel biodegradable polymer scaffolds with gradient structures and tailored mechanical properties is particularly attractive to enhance the repair efficiency of osteochondral defect.

In this thesis, two biodegradable polymers were investigated, flexible poly (glycerol sebacate) (PGS) and rigid poly(-caprolactone)-poly(ethylene glycol)-poly(-caprolactone) (PCL-PEG-PCL, PCEC), which were further fabricated into porous scaffolds via 3D printing. To enhance bioactivity, prechondrogenic collagen type I/II-hyaluronic acid (CI/II-HyA) and bone-active collagen type I-hydroxyapatite (CI-nHA) matrices were incorporated into PGS and PCEC scaffolds respectively, to create biomimetic CI/II-HyA@PGS and CI-nHA@PCEC composite scaffolds targeted for the cartilage layer and the subchondral bone layer. The processing, structure, mechanical properties, degradation behaviour of the isolated composite scaffolds as well as of the combined bilayer composite scaffold were systematically characterized. Additionally, the chondrogenic capability of the CI/II-HyA@PGS composite scaffold layer and the osteogenic capability of the CI-nHA@PCEC composite scaffold layer were investigated separately to evaluate the potential of the combined bilayer composite scaffold for application in osteochondral tissue engineering.

In summary, a novel bilayer biodegradable polymer scaffold was fabricated for osteochondral tissue engineering. It was made up of a CI/II-HyA matrix incorporated in a soft 3D-printed PGS scaffold as the cartilage layer, and a CI-nHA matrix incorporated into a rigid 3D-printed PCEC scaffold as the bone layer. Comprehensive characterizations revealed that the bilayer composite scaffold exhibited biomimetic composition and structure, gradient mechanical properties, compatible degradation rate with tissue regeneration, and effective chondrogenesis in top layer and osteogenesis in bottom layer, highlighting its potential for osteochondral tissue engineering.