Degradation behaviour of 3D printed poly(L-lactide-co-glycolide) scaffolds for cartilage tissue engineering

Osteoarthritis (OA) is a disease that affects over 240 million people worldwide with one-third of the population over 65 years displaying signs of OA[1][2]. Repairing the damaged cartilage using tissue engineering where the regeneration of the tissue is achieved by implanting a desired scaffolding matrix at the damaged site has been promising to alleviate OA. Despite significant advances, scientists have failed to regenerate cartilage tissue with the required structural and biomechanical properties. The degradation of scaffolds is an important factor in tissue regeneration. Poly(L-lactide-co-glycolide) (PLGA 85:15) bioresorbs in the body in around six months and can be a suitable material for cartilage regeneration. Therefore, this study aims to investigate the in-vitro degradation behaviour of these 3D-printed PLGA scaffolds. Investigating this degradation at physiologically relevant time scales (>6 months) is time-consuming and expensive, therefore the current study employs accelerated in vitro degradation methods [3]. The PLGA scaffolds (fibre diameter of 320μm, spacing of 1.7mm) with a double offset design were 3D printed using Bioscaffolder (GeSiM, Germany) as shown in Fig.1. The scaffolds were degraded in phosphate-buffered saline (PBS) under sterile conditions at 37ºC and elevated 47ºC temperatures and evaluated at specific time intervals for 6 weeks for their structural features, compressive properties, glass transition temperature, swelling, mass and pH changes. A compressive modulus of 5.5±1 MPa, equilibrium modulus of 3.58±1 MPa, and dynamic modulus of 20.81±1 MPa revealed comparable properties with the native cartilage. Degradation of the scaffolds under physiological conditions displayed a decrease in pH due to the release of acidic oligomers into PBS. The scaffolds underwent significant changes in mass and swelling due to the hydrophillic and porous nature of scaffolds. A decrease in the thermal and compressive properties was also observed during degradation. The decrease in the properties of the scaffold was enhanced at elevated temperature which further provides an insight on how the scaffold would degrade in the long-term. This project has demonstrated the capability of producing and evaluating the degradation behaviour of bioresorbable scaffolds.