Microfluidic engineering of CeO2/Peptide nanosheet-integrated bioactive hydrogel microspheres for multi-enzymatic biomimetic catalytic therapy of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by chronic inflammation and oxidative stress-induced cartilage degeneration, yet effective disease-modifying therapies remain limited. Herein, we report a CeO 2 /peptide nanosheet (CeP)-integrated hydrogel microsphere (CePHM) platform for multi-enzymatic biomimetic catalytic therapy of OA. Self-assembled peptide nanosheets (PNSs) serve as biocompatible two-dimensional scaffolds that uniformly disperse CeO 2 nanozymes, preventing nanozyme aggregation while preserving their intrinsic superoxide dismutase (SOD)-, catalase (CAT)-, and peroxidase (POD)-like activities. The CeP composite nanozymes are further encapsulated within microfluidically fabricated chitosan/β-glycerol phosphate hydrogel microspheres (~ 100 μm), which exhibit thermosensitive gelation and acid-responsive degradation, enabling localized retention and sustained release in the osteoarthritic joint microenvironment. Functionally, CePHM provides sustained reactive oxygen species (ROS) scavenging activity for more than 240 h, effectively reducing intracellular redox burden. In chondrocytes, CePHM attenuates oxidative stress, preserves mitochondrial membrane potential, and enhances the activity of endogenous antioxidant enzymes, including glutathione peroxidase (GSH-Px), CAT, and SOD. These cytoprotective effects are accompanied by downregulation of the catabolic marker matrix metalloproteinase 13 (MMP 13) and upregulation of cartilage-specific extracellular matrix components, including collagen II (Col II), aggrecan (ACAN), and SRY-box transcription factor 9 (Sox 9). Mechanistically, CePHM suppresses cartilage degeneration by inhibiting ROS-mediated activation of the NF-κB signaling pathway. In a destabilization of the medial meniscus (DMM)-induced OA rat model, intra-articular administration of CePHM markedly attenuated cartilage degeneration, preserved proteoglycan content, and improved subchondral bone remodeling. These findings demonstrate that CePHM represents a biocompatible, microenvironment-responsive nanozyme delivery platform with strong potential as a disease-modifying therapeutic strategy for OA.