Enzyme-responsive microgel with controlled drug release, lubrication and adhesion capability for osteoarthritis attenuation

The treatment of osteoarthritis (OA) remains challenging due to the narrow therapeutic window and rapid clearance of therapeutic agents, even with intra-articular administration, resulting in a low treatment index. Recent advancements in local drug delivery systems have yet to overcome the issues of uncontrolled burst release and short retention time, leading to suboptimal OA treatment outcome. Herein, we developed a methacrylatecrosslinking hyaluronic acid (HA) microgel (abbreviated as CXB-HA-CBP) that covalently conjugates the antiinflammatory drug celecoxib (CXB) via a metalloproteinase-2 (MMP-2)-responsive peptide linker (GGPLGLAGGC) and a collagen II binding peptide (WYRGRLC). The GGPLGLAGGC linker is specifically cleaved by the overexpressed MMP-2 enzyme within the OA joint, enabling the sustained and on-demand release of CXB entity. The synergistic action of CXB and HA effectively inhibited macrophage activation and reduced the production of pro-inflammatory cytokines, protecting chondrocytes from damage. Furthermore, the collagen II peptide introduced on the microgel surface enabled a cartilage-binding function to form an artificial lubrication microgel layer on the cartilage surface to reduce cartilage wear. The CXB-HA-CBP microgel showed an extended retention time of up to 18 days in the affected joint, leading to an effective OA treatment in rats. This sophistically designed microgel, characterized by the prolonged retention time, sustained drug delivery, and enhanced lubrication, presents a promising biomedicine for OA treatment. Statement of significance: A new methacrylate-crosslinking hyaluronic acid (HA) microgel, covalently conjugated with the celecoxib (CXB)-GGPLGLAGGC and the collagen II binding peptide (CBP, peptide sequence: WYRGRLC), was developed. The overexpressed MMP-2 in OA joint cleaved the GGPLGLAGGC linker to trigger the CXB moiety release. Besides, the CBP on the surface of microgels enabled a cartilage-attaching ability, resulting in a prolonged retention time and an improved lubrication property in joint. This advanced drug-loading microgel remarkably reduced macrophage activation and pro-inflammation cytokine production, while protecting the chondrocytes via a dual action of CXB and HA. This study demonstrated that the enzyme-responsive drug-loading microgel could serve as an platform to efficiently attenuate osteoarthritis.