Injectable lubricant-coated hyaluronic acid−dopamine for the repair of early osteoarthritis

Osteoarthritis (OA) is an irreversible disease of continuous degradation of cartilage, and natural joint super-lubrication is thought to provide hydrated lubrication to articular cartilage. Synovial joint fluid consists of hyaluronic acid (HA) and numerous brush-like macromolecules, exhibits a high affinity for cartilage proteins, and forms a hydrated layer on the cartilage surface. When cartilage friction increases, the surface layer of the cartilage becomes ruptured or damaged, and the cartilage hydration layer is destroyed, subsequently evolving into early OA. In this study, dopamine (DOPA) was coupled with HA to modify it by utilizing the hydrophilicity of HA and the adhesive properties of DOPA. On the one hand, it enhances cartilage lubrication by prolonging the retention time of HA in cartilage and restoring the hydrated layer on the cartilage surface by adhering to the type II collagen network. The successful synthesis of hyaluronic acid-DOPA (HAD) was confirmed by nuclear magnetic resonance (NMR) hydrogen spectroscopy, infrared spectroscopy, and ultraviolet (UV) absorption spectroscopy. The morphology and hydrophilicity of HAD were demonstrated using atomic force microscopy (AFM) and contact angle measurements. Additionally, the interaction of HAD with cartilage matrix proteins was verified through confocal microscopy imaging, while the biocompatibility and feasibility of injection of HAD were confirmed by cellular and animal experiments. On the other hand, the effect of protecting and even regenerating cartilage was achieved by remodeling the cartilage microenvironment. The cartilage protection and even regeneration ability of HAD was confirmed by injecting HAD at different times after OA modeling and characterizing the joints in sections.