Injectable hyaluronic acid-metformin conjugate gel for sustained intra-articular delivery and prevention of post-traumatic osteoarthritis.

We developed an injectable hyaluronic acid-metformin (HA-Met) conjugate gel for localized intra-articular delivery to mitigate post-traumatic osteoarthritis (PTOA). Conjugation was verified by Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and high-performance liquid chromatography. In vitro studies showed an initial 24-h burst attributable to unbound Met, followed by prolonged local retention from the conjugated fraction under physiological incubation without hyaluronidase treatment; by contrast, a simple HA + Met mixture released Met in phosphate-buffered saline (PBS) completely in 3 days. In high dosage hyaluronidase-containing PBS, Met retained in the HA-Met conjugate gel up to 4 days. In vivo, Met remained detectable in mouse knee tissues for up to 7 days after a single intra-articular injection of HA-Met conjugate and accumulated with weekly dosing; in contrast, after Met solution or HA + Met mixture injection around 99% of Met was removed from the knee joint in 1 day, low dosage traces of Met remained in the joint up to 2-3 days. In a destabilization of medial meniscus-induced murine PTOA model, weekly HA-Met conjugate injections attenuated cartilage degeneration and joint pathology versus HA or Met alone, which produced only modest effects; sham joints exhibited no pathological changes. The weekly interval was selected to ensure continuous exposure in mice with rapid metabolism and joint clearance and should be viewed as an accelerated proof-of-concept schedule rather than a clinical regimen. These findings support HA-Met conjugate gel as a translational platform that achieves prolonged intra-articular Met retention and disease-modifying benefit in a small-animal PTOA model.