A microenvironment-responsive microsphere–PLGA-PEG-PLGA hydrogel for sustained and coordinated co-delivery of celecoxib and ropivacaine in osteoarthritis therapy

In this study, celecoxib (CXB) microspheres (CM) and ropivacaine (RPV) microspheres (RM) were prepared respectively. A poly (D, L-lactide-co-glycolide)-block-poly (ethylene glycol)-block-poly (D, L-lactide-co-glycolide) (PLGA–PEG–PLGA, PPP) was synthesized by copolymerizing glycolide and lactide with polyethylene glycol. CM, RM, and hydroxyapatite (HA) were then incorporated into PPP solution to construct the microsphere–hydrogel system (CRMH hydrogels). CM, RM, and CRMH were systematically characterized in terms of morphology, physicochemical properties, pH-buffering capacity, and degradation behavior. The pH-dependent drug release and release kinetics of the individual CM, RM and the CRMH hydrogels were also investigated. In vitro release studies demonstrated that CRMH hydrogels provided coordinated, sustained release of CXB and RPV at pH 6.2. In a rabbit osteoarthritis (OA) model, intra-articular (IA) administration of CRMH hydrogels achieved sustained drug retention and release within the joint cavity, and effectively promoted articular cartilage repair. Overall, the CRMH hydrogels showed promising synergistic therapeutic potential for OA.