title: Tribological efficacy and stability of phospholipid-based membrane lubricants in varying pH chemical conditions.
abstract: In this study, the authors examine the influence of joint chemical environment by measuring changes in the tribological properties (friction coefficient and charge density) of contacting surfaces of normal and degenerated cartilage samples in bath solutions of varying pH (2.0-9.0). Bovine articular cartilage samples (n = 54) were subjected to several surface measurements, including interfacial energy, contact angle, and friction coefficient, at varying pH. The samples were delipidized and then subjected to the same measurement protocols. Our results reveal that the interfacial energy and charge density, which have been shown to be related to friction coefficient, decrease with pH in the acidic range and approach constant values at physiological (or synovial fluid) pH of 7.4 and beyond it, i.e., toward basic pH domain. The authors conclude that this rather complex response explains the long-term efficacy with respect to ageing and associated pH changes, of the phospholipid layers that facilitate the almost frictionless, hydration-lubrication involving contact in the mammalian musculoskeletal system.
authors.affiliation: Tribochemistry Consulting, Salt Lake City, Utah 84117 and Kujawsko-Pomorska University in Bydgoszcz, Toruńska 55-57, 85-023 Bydgoszcz, Poland.
authors.forename: Zenon
authors.initials: Z
authors.lastname: Pawlak
authors.affiliation: Faculty of Mathematics, Physics and Technical Sciences, Kazimierz Wielki University, 85-867 Bydgoszcz, Chodkiewicza 30, Poland and Kujawska University, Plac Wolności 1, 87-800 Włocławek, Poland.
authors.forename: Wieslaw
authors.initials: W
authors.lastname: Urbaniak
authors.affiliation: Department of Electrical and Computer Engineering, Elizade University, Ilara-Mokin P.M.B.344, Ondo State, Nigeria and Department of Applied Physics, University of Eastern Finland, Kuopio 770211, Finland.
authors.forename: Isaac O
authors.initials: IO
authors.lastname: Afara
authors.affiliation: College of Medical Rehabilitation Sciences, Department of Prosthetics and Orthotics, Taibah University, Universities Road, P.O. Box: 344, Madinah, Kingdom of Saudi Arabia.
authors.forename: Kehinde Q
authors.initials: KQ
authors.lastname: Yusuf
authors.affiliation: Faculty of Mathematics, Physics and Technical Sciences, Kazimierz Wielki University, Powstancow Wielkopolskich 2, 85-090 Bydgoszcz, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Banaszak-Piechowska
authors.affiliation: Department of Electrical and Computer Engineering, Elizade University, Ilara-Mokin P.M.B.344, Ondo State, Nigeria.
authors.forename: Adekunle
authors.initials: A
authors.lastname: Oloyede
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000737:chemistry* / Q000502:physiology*; D002417:Cattle; D017276:Friction; D006863:Hydrogen-Ion Concentration; D054327:Lubricants / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*
chemical_list: D054327:Lubricants; D010743:Phospholipids