AVS 50th International Symposium
    Biomaterial Interfaces Monday Sessions
       Session BI-MoA

Paper BI-MoA9
Boundary Lubrication Properties of Bio- and Synthetic Polymers Containing Poly- and Oligosaccharides

Monday, November 3, 2003, 4:40 pm, Room 307

Session: Non-fouling Surfaces and Biolubrication
Presenter: S. Lee, ETH-Zürich, Switzerland
Authors: S. Lee, ETH-Zürich, Switzerland
G. Kilcher, ETH-Zürich, Switzerland
N.D. Spencer, ETH-Zürich, Switzerland
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In this study, we have investigated the boundary-lubrication properties of aqueous solutions of natural and synthetic polymers possessing poly- and/or oligosaccarides as an additive to reduce interfacial friction forces. As natural polymers containing poly- and oligosaccarides, we have chosen porcine gastric mucin (PGM) as a standard material responsible for bio-lubrication. Mucins are large and complex glycoproteins composed of a linear polypeptide and polysaccarides side-chains. Due to their aggregation or polymerization, often involving gel formation, mucins are known to form a protective layer between the lumen and the cell surface. Mucins possess a structure involving a combination of hydrophilic and hydrophobic domains with high molecular weight. The boundary lubrication properties of PGM-containing aqueous solutions have been investigated on hydrophobic tribo-pairs, such as self-mated poly(dimethylsiloxane) (PDMS). To more systematically investigate the role of poly- and/or oligosaccarides for water-based lubrication, we have synthesized block copolymers consisting of a polypeptide backbone, e.g. poly(L-lysine), and oligosaccarides with well-defined structure and chemistry. For this model system, we have selected various oxide surfaces as a tribo-pair. Both macroscopic- and molecular-scale sliding contact have been investigated employing pin-on-disk tribometry and atomic force microscopy respectively. The frictional properties of the selected tribosystem have been measured as a function of pH and ionic strength/type of the aqueous lubricant solution. The observed changes of the lubrication properties of both bio- and synthetic polymers as a function of pH and ionic strength are discussed in terms of the corresponding changes of conformation and adsorption behavior.