Fabrication and characterization of composite GelMA and nHAp scaffolds for osteochondral tissue engineering

Abstract

Osteochondral (OC) tissue regeneration remains a significant challenge due to the complex gradient in structure, composition, and mechanical properties between cartilage and subchondral bone. Current scaffold systems tend to lack the ability to reproduce the hierarchical structure and offer adequate mechanical strength required to perform functional repair. In the research, a new type of tri-layered scaffold made of gelatin Methacryloyl (GelMA), polycaprolactone (PCL), and nano-hydroxyapatite (nHAp) was developed to be as close as possible to the natural osteochondral interface. The scaffold was produced through a composite method of solvent casting, electrospinning, UV photocrosslinking and freeze-drying to produce a cartilage-like GelMA layer, a bone-like GelMA-nHAp layer and an electrospun PCL mesh as a biomimetic tidemark. One of the central innovations of this work is the design of the acellular scaffold and a long-term UV photocrosslinking process, which allows a higher crosslink density and structural stability without restrictions on the presence of cells, which induce cytotoxicity. Such strategy enabled systematic optimization of mechanical and physicochemical properties, which is typically limited in traditional cell-laden systems. FTIR, mechanical testing, rheological analysis, TGA, SEM, and EDX were used to perform comprehensive characterization. FTIR analysis confirmed successful methacrylation of gelatin, validating GelMA synthesis. Mechanical testing revealed that native OC tissues had a much higher Young’s modulus (0.4-0.6 MPa) than the scaffold (~0.1 MPa), showing that the scaffold is softer, but more deformable. Remarkably, dry scaffolds performed better in mechanical terms than in hydrated conditions, which emphasized the importance of plasticization of hydrogel systems by water...