title: Binding and lubrication of biomimetic boundary lubricants on articular cartilage.
abstract: The glycoprotein, lubricin, is the primary boundary lubricant of articular cartilage and has been shown to prevent cartilage damage after joint injury. In this study, a library of eight bottle-brush copolymers were synthesized to mimic the structure and function of lubricin. Polyethylene glycol (PEG) grafted onto a polyacrylic acid (pAA) core mimicked the hydrophilic mucin-like domain of lubricin, and a thiol terminus anchored the polymers to cartilage surfaces much like lubricin's C-terminus. These copolymers, abbreviated as pAA-g-PEG, rapidly bound to cartilage surfaces with binding time constants ranging from 20 to 39 min, and affected lubrication under boundary mode conditions with coefficients of friction ranging from 0.140 ± 0.024 to 0.248 ± 0.030. Binding and lubrication were highly correlated (r2= 0.89-0.99), showing that boundary lubrication in this case strongly depends on the binding of the lubricant to the surface. Along with time-dependent and dose-dependent behavior, lubrication and binding of the lubricin-mimetics also depended on copolymer structural parameters including pAA backbone length, PEG side chain length, and PEG:AA brush density. Polymers with larger backbone sizes, brush sizes, or brush densities took longer to bind (p < 0.05). Six of the eight polymers reduced friction relative to denuded cartilage plugs (p < 0.05), suggesting their potential to lubricate and protect cartilage in vivo. In copolymers with shorter pAA backbones, increasing hydrodynamic size inhibited lubrication (p < 0.08), while the opposite was observed in copolymers with longer backbones (p < 0.05). These polymers show similar in vitro lubricating efficacy as recombinant lubricins and as such have potential for in vivo treatment of post-traumatic osteoarthritis. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:548-557, 2017.
authors.affiliation: Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York.
authors.forename: Kirk J
authors.initials: KJ
authors.lastname: Samaroo
authors.affiliation: Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, 149 Weill Hall, Ithaca, New York, 14853.
authors.forename: Mingchee
authors.initials: M
authors.lastname: Tan
authors.affiliation: Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, 149 Weill Hall, Ithaca, New York, 14853.|School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York.
authors.forename: David
authors.initials: D
authors.lastname: Putnam
authors.affiliation: Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York.|Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, 149 Weill Hall, Ithaca, New York, 14853.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Bonassar
mesh_terms: D000818:Animals; D040761:Biomimetic Materials / Q000138:chemical synthesis*; D002358:Cartilage, Articular / Q000737:chemistry*; D002417:Cattle; D006023:Glycoproteins / Q000737:chemistry; D054327:Lubricants / Q000138:chemical synthesis*; D013329:Structure-Activity Relationship; D000099158:Proteoglycan 4
chemical_list: D006023:Glycoproteins; D054327:Lubricants; D000099158:Proteoglycan 4
keywords: boundary lubrication; cartilage; lubricin; lubricin-mimetic; osteoarthritis