Adsorption, lubrication, and wear of lubricin on model surfaces: polymer brush-like behavior of a glycoprotein.
Adsorption, lubrication, and wear of lubricin on model surfaces: polymer brush-like behavior of a glycoprotein.
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DOI：
10.1529/biophysj.106.088799
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发表时间：
2007-03
影响因子：
3.4
通讯作者：
B. Zappone;M. Ruths;G. Greene;G. Jay;J. Israelachvili
中科院分区：
文献类型：
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作者：
B. Zappone;M. Ruths;G. Greene;G. Jay;J. Israelachvili
使用表面力装置，我们测量了人糖蛋白润滑素层之间的法向力和摩擦力，润滑素是关节中的主要边界润滑剂，从缓冲盐水溶液中吸附在各种亲水性和疏水性表面上：i），带负电荷的云母，ii），带正电荷的聚赖氨酸和氨基硫醇，和iii），疏水性的烷醇单分子层。在所有这些表面上，润滑素形成厚度为60-100 nm的致密吸附层。两个表面之间的法向力总是排斥的，并且类似于末端接枝聚合物刷层之间测量的空间熵力。这是润滑素在临床试验中显示的抗粘连特性背后的微观机制。对于高达约6atm的压力，润滑素润滑亲水表面，特别是带负电荷的云母（摩擦系数μ = 0.02-0.04），比疏水表面（μ> 0.3）好得多。在较高的压力下，对于所考虑的所有表面，摩擦系数较高（μ> 0.2），并且润滑剂层在剪切下重新排列。然而，糖蛋白仍然保护底层底物免受高达高得多的压力的损害。这些结果支持了最近的建议，边界润滑和磨损保护关节是由于存在的软骨表面上的生物涂层。
Using a surface force apparatus, we have measured the normal and friction forces between layers of the human glycoprotein lubricin, the major boundary lubricant in articular joints, adsorbed from buffered saline solution on various hydrophilic and hydrophobic surfaces: i), negatively charged mica, ii), positively charged poly-lysine and aminothiol, and iii), hydrophobic alkanethiol monolayers. On all these surfaces lubricin forms dense adsorbed layers of thickness 60-100 nm. The normal force between two surfaces is always repulsive and resembles the steric entropic force measured between layers of end-grafted polymer brushes. This is the microscopic mechanism behind the antiadhesive properties showed by lubricin in clinical tests. For pressures up to approximately 6 atm, lubricin lubricates hydrophilic surfaces, in particular negatively charged mica (friction coefficient mu = 0.02-0.04), much better than hydrophobic surfaces (mu > 0.3). At higher pressures, the friction coefficient is higher (mu > 0.2) for all surfaces considered and the lubricin layers rearrange under shear. However, the glycoprotein still protects the underlying substrate from damage up to much higher pressures. These results support recent suggestions that boundary lubrication and wear protection in articular joints are due to the presence of a biological polyelectrolyte on the cartilage surfaces.