Lubrication and load-bearing properties of human salivary pellicles adsorbed ex vivo on molecularly smooth substrata

Harvey, Neale M., Yakubov, Gleb E., Stokes, Jason R. and Klein, Jacob (2012) Lubrication and load-bearing properties of human salivary pellicles adsorbed ex vivo on molecularly smooth substrata. Biofouling, 28 8: 843-856. doi:10.1080/08927014.2012.714777

Author Harvey, Neale M.
Yakubov, Gleb E.
Stokes, Jason R.
Klein, Jacob
Title Lubrication and load-bearing properties of human salivary pellicles adsorbed ex vivo on molecularly smooth substrata
Journal name Biofouling   Check publisher's open access policy
ISSN 0892-7014
Publication date 2012
Year available 2012
Sub-type Article (original research)
DOI 10.1080/08927014.2012.714777
Open Access Status
Volume 28
Issue 8
Start page 843
End page 856
Total pages 14
Place of publication Abingdon, Oxfordshire, United Kingdom
Publisher Taylor and Francis
Collection year 2013
Language eng
Subject 1104 Complementary and Alternative Medicine
2312 Water Science and Technology
2402 Applied Microbiology and Biotechnology
Abstract In a series of Surface Force Balance experiments, material from human whole saliva was adsorbed to molecularly smooth mica substrata (to form an 'adsorbed salivary film'). Measurements were taken of normal (load bearing, Fn) and shear (frictional, Fs*) forces between two interacting surfaces. One investigation involved a salivary film formed by overnight adsorption from undiluted, centrifuged saliva, with the adsorbed film rinsed with pure water before measurement. Measurements were taken under pure water and 70 mM NaNO3. In a second investigation, a film was formed from and measured under a solution of 7% filtered saliva in 10 mM NaNO3. Fn results for both systems showed purely repulsive layers, with an uncompressed thickness of 35-70 nm for the diluted saliva investigation and, prior to the application of shear, 11 nm for the rinsed system. Fs* was essentially proportional to Fn for all systems and independent of shear speed (in the range 100-2000 nm s-1), with coefficients of friction μ ~ 0.24 and μ ~ 0.46 for the unrinsed and rinsed systems, respectively. All properties of the rinsed system remained similar when the pure water measurement environment was changed to 70 mM NaNO3. For all systems studied, shear gave rise to an approximately threefold increase in the range of normal forces, attributed to the ploughing up of adsorbed material during shear to form debris that stood proud of the adsorbed layer. The results provide a microscopic demonstration of the wear process for a salivary film under shear and may be of particular interest for understanding the implications for in vivo oral lubrication under conditions such as rinsing of the mouth cavity. The work is interpreted in light of earlier studies that showed a structural collapse and increase in friction for an adsorbed salivary film in an environment of low ionic strength.
Keyword Film
Shear Force
Surface Forces
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
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Citation counts: TR Web of Science Citation Count  Cited 10 times in Thomson Reuters Web of Science Article | Citations
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