title: Characterization of protein degradation in serum-based lubricants during simulation wear testing of metal-on-metal hip prostheses.
abstract: A size exclusion high performance liquid chromatography (SEC-HPLC) method has been developed which is capable of separation and quantitation of bovine serum albumin (BSA) and bovine serum globulin (BSG) components of serum-based lubricant (SBL) solutions. This allowed characterization of the stability profiles of these proteins when acting as lubricants during hip wear simulation, and identification of wear-specific mechanisms of degradation. Using cobalt-chromium metal-on-metal (MOM) hip joints, it was observed that BSA remained stable for up to 3 days (215K cycles) of wear testing after which the protein degraded in a fairly linear fashion. BSG on the other hand, began to degrade immediately and in a linear fashion with a rate constant of 5% per day. Loss of both proteins occurred via the formation of high molecular weight aggregates which precipitated out of solution. No fragmentation of the polypeptide backbone of either protein was observed. Data obtained suggest that protein degradation was not due to microbial contamination, denaturation at the air-water interface, or frictional heating of articulating joint surfaces in these studies. We conclude that the primary source of protein degradation during MOM simulation testing occurs via high shear rates experienced by SBL solutions at articulating surfaces, possibly coupled with metal-protein interactions occurring as new and reactive metal surfaces are generated during wear testing. The development of this analytical methodology will allow new studies to clarify the role of SBL solutions in wear simulation studies and the interactions and lubricating properties of serum proteins with prosthetic surfaces other than MOM.
authors.affiliation: Department of Pharmaceutical Sciences, Loma Linda University School of Pharmacy, Loma Linda, California 92354.
authors.forename: Victoria K
authors.initials: VK
authors.lastname: Maskiewicz
authors.affiliation: Department of Orthopaedic Surgery, Loma Linda University School of Medicine, Loma Linda, California 11406.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Williams
authors.affiliation: Department of Pharmaceutical Sciences, Loma Linda University School of Pharmacy, Loma Linda, California 92354.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Prates
authors.affiliation: Department of Orthopedic Surgery, Peterson Tribology Research Center, Loma Linda University School of Medicine, Loma Linda, California 11406.
authors.forename: John G
authors.initials: JG
authors.lastname: Bowsher
authors.affiliation: Department of Orthopedic Surgery, Peterson Tribology Research Center, Loma Linda University School of Medicine, Loma Linda, California 11406.
authors.forename: Ian C
authors.initials: IC
authors.lastname: Clarke
mesh_terms: D000818:Animals; D002857:Chromium; D003035:Cobalt; D006622:Hip Prosthesis / Q000592:standards*; D006801:Humans; D054327:Lubricants / Q000737:chemistry / Q000592:standards*; D008422:Materials Testing / Q000379:methods*; D008670:Metals; D011489:Protein Denaturation; D055550:Protein Stability; D012709:Serum Albumin; D012712:Serum Globulins
chemical_list: D054327:Lubricants; D008670:Metals; D012709:Serum Albumin; D012712:Serum Globulins; D002857:Chromium; D003035:Cobalt