Biomechanics and Implant Design

Biography

Biography: Zenon Pawlak

Abstract

The chemical and physical nature of  biological surfaces is seen in an entirely different light than that of engineering surfaces immersed  in water.  The lubrication mechanisms in an animal body, where the the surfaces are coated with  phospholipid (PLs) bilayers, with (PLs)  lamellar phases and charged biomacromolecules in synovial fluid, have been referred to as a “lamellar-repulsive” mechanism [1, 2].  Amphoteric (PLs) are the main solid-phase lubricant on the surface of an articular cartilage (AC).  The lubricant is chemically attached to the surface, and is responsible for the biological lamellar-repulsive lubrication  mechanism.  It has been well established that the PLs bilayers mechanism, which essentially consists of a surface amorphous layer (SAL) surrounded by a 0.155 M electrolyte synovial fluid (SF) of pH ~7.4 with high-molecular-weight charged biomacromolecules, supports low friction.  Both the friction and wettability show very similar behavior as the SAL thickness is varied.  The SAL, phospholipidic lamellar phases and biomacromolecules in SF, are expected to cover cartilage surfaces and support hydrophilic lubrication.  Hydration  repulsion dominates the interaction between charged cartilage surfaces at nanometer separations and ultimately prevents sticking together of cartilage surfaces, even at as high pressures as 100 MPa.  In this presentation, we demonstrate experimentally that the pH sensitivity of cartilage to friction  provides a novel concept in joint lubrication on charged surfaces. [1] Pawlak Z.  et al. Lamellar slippage of bilayers—A hypothesis on low friction of natural joints.  Biointerphases, (2014) 9. DOI:10.1116/1.4902805 (2014). [2] Pawlak Z. et al. The probable explanation for the low friction of natural joints. Cell Biochemistry and Biophysics.  (2015) 71, 1615-1621.