A snowboard-inspired lubricating nanosystem with responsive drug release for osteoarthritis therapy.

Most of present works of osteoarthritis (OA) therapy are focusing on reducing friction and improving drug loading capacity, while little attention is paid to realizing long-time lubrication and on-demand drug release. In this study, inspired by snowboards with good solid-liquid interface lubrication, a fluorinated graphene based nanosystem with dual functions of long-time lubrication and thermal-responsive drug release was constructed for OA synergetic therapy. An aminated polyethylene glycol bridging strategy was developed to enable covalent grafting of hyaluronic acid on fluorinated graphene. This design not only greatly increased the nanosystem's biocompatibility, but also reduced the coefficient of friction (COF) by 83.3 % compared to H2O. The nanosystem showed long-time and steady aqueous lubrication behavior even after more than 24,000 times of friction tests, and a low COF of 0.13 was obtained with over 90% wear volume reduction. Diclofenac sodium was controllably loaded and sustained drug release was tuned by near-infrared light. Moreover, anti-inflammation results showed that the nanosystem had good protective effect on inhibiting OA deterioration, which could up-regulate cartilage anabolic genes of Col2α and aggrecan while down-regulating catabolic proteases genes of TAC1 and MMP1. This work constructs a novel dual-functional nanosystem that realizes friction and wear reduction with long lubrication life, and shows thermal-responsive on-demand drug release with good synergistic therapeutic effect of OA.