Biomimetic lubricating COFs with donor-acceptor structure for osteoarthritis therapy

Covalent organic framework (COF) possesses special chemical bonds and unique structure and holds great promise in osteoarthritis (OA) therapy. However, non-dispersion in water and single function heavily hinder its further applications. Herein, a donor-acceptor structured biomimetic COF with long-term water dispersing stability, high phototerhmal responsiveness and on-demand drug release for joint lubrication is developed. The designed D-A structure provides effective carrier transport pathways and channels to change near-infrared (NIR) light into heat, and fine control over covalent bonds and reaction conditions endows well-aligned porous structure for drug loading. Biomimetic function with polydopamine provides enriched hydrophilic chemical groups for robust water-dispersity and adhesion, and constructs a hard-soft lubricating system that greatly reduce friction and wear under various conditions for more than 10,800 times without failure. The lubricating system possesses benign cytocompatibility, can be readily taken up into chondrocyte and shows responsively sustained drug release, which achieves anti-inflammatory effects by upregulating the expression levels of Col2α, Aggrecan and downregulating MMP1 and TAC1 mRNA in chondrocytes. We also demonstrate its first experimental example of promoting cell proliferation and migration. Our research suggests an encouraging biomimetic method for combining COF with distinctive structure and multiple functionalities, aiming at an efficient synergistic management of OA.