Synthetic Lubrication of Bone Interfaces for Late-Stage Osteoarthritis Treatment

In the late stage of osteoarthritis (OA), few options are available to improve patient quality of life beyond joint arthroplasty. Exposed bone and direct bone-on-bone contact in late-stage OA lead to severe pain and joint stiffness. These symptoms could potentially be relieved through sufficient lubrication of the bone surface. Herein, we report a diblock copolymer that significantly reduces the coefficient of friction at bone interfaces. One block of the copolymer contains positively charged quaternary amines that are designed to electrostatically interact with the negatively charged bone mineral composite, and the other block resists compression to lubricate the interface by a bottle-brush structure consisting of poly(acrylic acid) backbones and polyethylene glycol side chains. The diblock copolymer effectively lubricated the bone surface to a level that is superior (trabecular bone) or comparable (subchondral bone) to the coefficient of friction of cartilage in phosphate buffered saline under boundary mode conditions. To our knowledge, this is the first study showing effective bone lubrication via a synthetic lubricant and thus could serve as a potential treatment for late-stage OA when bone surfaces are exposed.