AVS 53rd International Symposium
    Biomaterial Interfaces Thursday Sessions
       Session BI+AS-ThA

Paper BI+AS-ThA8
NanoTribological Studies on the Mechanisms of O-Linked Glycosylated Proteins in the Boundary-Lubrication of Articular Cartilage

Thursday, November 16, 2006, 4:20 pm, Room 2014

Session: Biomolecule-Surface Characterization I
Presenter: D. Chang, Duke University
Authors: S. Zauscher, Duke University
N.I. Abu-Lail, Duke University
D. Chang, Duke University
F. Guilak, Duke University
G. Jay, Brown University
Correspondent: Click to Email
The diarthroidal (synovial) joints of the body enable locomotion and activity while withstanding millions of loading cycles, which may be several times body weight. Recent macroscopic tribological experiments and biochemical analyses suggest that heavily glycosylated proteoglycans, encoded by gene proteoglycan 4 (PRG4) and expressed by synoviocytes in synovial fluid as lubricin and by chondrocytes on the superficial zone of articular cartilage as surface zone protein (SZP), provide boundary lubrication in cartilage in the absence of interstitial fluid pressurization. We will present results from nanotribo-mechanical measurements on model surfaces and cartilage, combined with other surface specific physicochemical measurements that shed new light on the mechanisms by which lubricin/SZP provides lubrication and wear protection in diarthroidal joints. Our results suggest that the role of effective boundary lubricants in mediating friction in articular joints is largely one of wear protection of surface asperities, maintaining the surfaces in a nonadhesive mode, and causing shear dissipation in the biopolymeric boundary lubricant layer, even at the cost of attaining "high" coefficients of friction (COF ~ 0.15). Lubricin's ability to form intermolecular disulfide bonds appears to be critical for its ability to develop large steric repulsion forces. Our results contribute significantly to the understanding of the conformation and physico-chemical function of mucinous glycoproteins on biological interfaces.