This study presents new insights into the potential role of polyelectrolyte interfaces in regulating low friction and interstitial fluid pressurization of cartilage. Polymer brushes composed of hydrophilic 3-sulfopropyl methacrylate potassium salt (SPMK) tethered to a PEEK substrate (SPMK-g-PEEK) are a compelling biomimetic solution for interfacing with cartilage, inspired by the natural lubricating biopolyelectrolyte constituents of synovial fluid. These SPMK-g-PEEK surfaces exhibit a hydrated compliant layer approximately 5 μm thick, demonstrating the ability to maintain low friction coefficients (μ ∼ 0.01) across a wide speed range (0.1–200 mm/s) under physiological loads (0.75–1.2 MPa). A novel polyelectrolyte-enhanced tribological rehydration mechanism is elucidated, capable of recovering up to ∼12% cartilage strain and subsequently facilitating cartilage interstitial fluid recovery, under loads ranging from 0.25 to 2.21 MPa. This is attributed to the combined effects of fluid confinement within the contact gap and the enhanced elastohydrodynamic behavior of polymer brushes. Contrary to conventional theories that emphasize interstitial fluid pressurization in regulating cartilage lubrication, this work demonstrates that SPMK-g-PEEK’s frictional behavior with cartilage is independent of these factors and provides unabating aqueous lubrication. Polyelectrolyte-enhanced tribological rehydration can occur within a static contact area and operates independently of known mechanisms of cartilage interstitial fluid recovery established for converging or migrating cartilage contacts. These findings challenge existing paradigms, proposing a novel polyelectrolyte–cartilage tribological mechanism not exclusively reliant on interstitial fluid pressurization or cartilage contact geometry. The implications of this research extend to a broader understanding of synovial joint lubrication, offering insights into the development of joint replacement materials that more accurately replicate the natural functionality of cartilage.

中文翻译：

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加强软骨润滑：聚电解质增强摩擦补水


这项研究对聚电解质界面在调节软骨低摩擦和间质液加压方面的潜在作用提出了新的见解。由亲水性 3-磺基甲基丙烯酸甲酯钾盐 (SPMK) 与 PEEK 基材 (SPMK-g-PEEK) 组成的聚合物刷是一种引人注目的与软骨连接的仿生解决方案，其灵感来自滑液的天然润滑生物聚电解质成分。这些 SPMK-g-PEEK 表面具有约 5 μm 厚的水合柔顺层，表现出在生理负荷 (0.75–1.2) 下在较宽的速度范围 (0.1–200 mm/s) 下保持低摩擦系数 (μ ∼ 0.01) 的能力。兆帕）。阐明了一种新型聚电解质增强摩擦学再水合机制，在 0.25 至 2.21 MPa 的载荷下，能够恢复高达 ∼12% 的软骨应变，并随后促进软骨间质液恢复。这是由于接触间隙内的流体限制和聚合物刷增强的弹性流体动力学行为的综合作用。与强调间质液加压调节软骨润滑的传统理论相反，这项工作表明 SPMK-g-PEEK 与软骨的摩擦行为独立于这些因素，并提供不减弱的水润滑。聚电解质增强的摩擦学再水化可以在静态接触区域内发生，并且独立于为会聚或迁移软骨接触而建立的已知的软骨间质液恢复机制而操作。 这些发现挑战了现有的范式，提出了一种新颖的聚电解质-软骨摩擦学机制，该机制不仅仅依赖于间质液加压或软骨接触几何形状。这项研究的意义在于更广泛地了解滑膜关节润滑，为开发更准确地复制软骨自然功能的关节置换材料提供见解。