Molecular Dynamics Simulation of the Hydration Lubrication Mechanism of CS-MPC/CS-ChS NPs.

Osteoarthritis (OA) remains a significant clinical challenge, with current treatments like sodium hyaluronate injections offering limited efficacy due to suboptimal lubrication and rapid degradation. In this study, we explored an advanced solution to these issues by investigating the colubrication mechanism of a composite biolubricant consisting of 2-methacryloyloxyethyl phosphorylcholine-modified chitosan (CS-MPC) and chondroitin sulfate-modified chitosan nanoparticles (CS-ChS NPs) using molecular dynamics (MD) simulations. Results show that the composite lubricant outperforms individual CS-MPC or CS-ChS NPs, exhibiting a lower coefficient of friction (COF) and a superior load-bearing capacity. The CS-MPC/CS-ChS NP system maintains a consistent compression ratio of -0.5% under different external pressures and exhibited a low coefficient of friction (COF) of 0.041 across varying shear velocities. The sulfate groups on CS-ChS NPs interact with CS-MPC chains, stabilizing the system through electrostatic interactions and enabling the effective dispersion of normal stress, thereby protecting the substrate surface from wear. This enhanced performance is attributed to the formation of a multilayered hydration shell around the lubricant molecules. The hydration shells provide superior lubrication, contributing to the system's robustness under varying loads. These findings offer critical insights into designing high-performance biolubricants for joint protection, presenting a promising avenue for future OA treatments.