Articular Cartilage: Chemical, Physical, and Tribological Properties - Articular Cartilage: Chemical, Physical, and Tribological Properties - Open Access Pub

The cartilage surface was characterized using wettability test fresh and depleted AC samples. In this work, we demonstrated experimentally that the cartilage smart biomaterial at varies pH is sensitive to friction and introduces a novel concept in joint lubrication on charged surfaces.The surface charge density of the articular cartilage surface is related to the amphoteric character of phospholipids, PLs functional groups (-NH3+) and (-PO4-). The maximum surface energy of AC was found to occur at pH for isoelectric point ~4.5 (H3N+(CH2)n PO4- -R1R2) and with a wide range minimum of pH 6.5 to 9.5 of the phospholipidic membrane covering biological pH ~7.4 lubrication condition. The hydrophilic and hydrophobic character of cartilage was determined. DOI 10.14302/issn.2377-2549.jndc-18-2159 The chemical and physical nature of the biological surfaces is seen in an entirely different light than that of engineering surfaces immersed in water. Author 1 attempts to explain a new joint lubrication mechanism with surface-active phospholipids (PLs) as a lubricant. Joint lubrication is a complex problem and attributing macromolecules to the synovial fluid of the lubricant cannot fulfill all the functions. The self-organization process of a stable pore structure in phospholipid liposomes, bilayers, lamellar phases in the synovial fluid forces the lamellar-repulsive mechanism of lubrication. The lubricant is chemically attached to the surface, and is responsible for the biological lubrication mechanism 1, 2, 3. The lamellar-repulsive joint lubrication mechanism is not so well-known in biotribology and therefore deserves to be published. The determination of the biophysical and biochemical parameters of articular cartilage and introduction a new mechanism of lubrication in natural joints was an idea of “Articular cartilage: lamellar-repulsive lubrication of natural joints” publication 1. The articular cartilage (AC) surface charge density is related to the amphoteric character of phospholipids (PLs) since they contain both (-NH3+) and (-PO4-) group. Previous research mainly focused on examining the contribution of macromolecules to joint lubrication. While in this paper, the authors attempt to explain a joint lubrication mechanism in such a way that the AC surface phospholipids can act significantly as a lubricant. To prove the hypothesis, two experiments were used. In the first one, the authors attempt to determine that AC surface with phospholipids undergo the conformational change in air-dry conditions. The second experiment attempts to determine the correlation