A fluorescent hyaluronic acid-gelatin hydrogel for traceable articular cartilage regeneration.

Post-traumatic osteoarthritis remains a significant clinical challenge, with limited effective treatment options. Conventional hydrogels for articular cartilage repair primarily focus on the bioactivity of the materials but often overlook the importance of monitoring the hydrogel's behavior in situ. This study presents the development of a novel injectable, traceable fluorescent hydrogel designed to prevent cartilage degradation and promote cartilage regeneration. The hydrogel was synthesized by forming a dynamically crosslinked network of oxidized hyaluronic acid (OHA) and adipic dihydrazide-grafted HA (HA-ADH), followed by photo-crosslinking with methacrylated gelatin (GelMA). Furthermore, GelMA was covalently conjugated with Rhodamine B, enabling real-time tracking of hydrogel degradation in situ. Experimental results demonstrated that the fluorescence of the hydrogel could effectively penetrate both skin and cartilage tissues, allowing for real-time monitoring. Additionally, the hydrogel exhibited superior lubrication (with a coefficient of friction of 0.134, comparable to HA) and favorable rheological properties, along with excellent biocompatibility. It also promoted cell differentiation and migration. In vivo studies showed that the hydrogel facilitated cartilage repair and prevented cartilage degradation over a 56-day period. Given its mechanical properties, biocompatibility, and fluorescence-based monitoring capability, this hydrogel shows great promise for real-time tracking in cartilage repair for the treatment of post-traumatic osteoarthritis.