Association of Polyethylene Friction and Thermal Unfolding of Interfacial Albumin Molecules
Resource
APPLIED SURFACE SCIENCE v.253 n.16 pp.6896-6904
Journal
APPLIED SURFACE SCIENCE
Journal Volume
v.253
Journal Issue
n.16
Pages
6896-6904
Date Issued
2007
Date
2007
Author(s)
FANG, HSU-WEI
ZHAO, JIAN-HUA
HUANG, HUEI-TING
LIN, HSIN-YI
LIU, HSUAN-LIANG
CHANG, CHIH-HUNG
YANG, CHARNG-BIN
LIU, HWA -CHANG
Abstract
Under the articulation of artificial joints, ultra-high molecular weight polyethylene (UHMWPE) acts as a bearing surface under the lubrication of synovial fluid containing various proteins. Albumin is the most abundant composition and acts as the interfacial molecule in the boundary lubrication regime. The dissipated energy including thermal energy from the tribological process may lead to the conformational change of albumin molecules. In this study, a series of experiments were designed and carried out to investigate the association of thermal unfolding albumin and the frictional characteristics of highly-crosslinked UHMWPE (x-UHMWPE) . An accelerated oxidation experiment was used to prepare x-UHMWPE with an oxidized surface. Analysis of the albumin protein by circular dichroism ( CD) spectroscopy was performed to detect the conformational changes during a thermal process. In addition,a molecular simulation was performed to understand the structural change of albumin at various temperatures and the exposed hydrophobic contact areas. Linear reciprocating frictional tests were carried out to obtain the start-up friction coefficients. The results indicate that a decrease of a.-helix content and an unfolding of the secondary structure of albumin were observed with increasing temperatures which may come from the frictional heat of joint articulation process. The conformational change of albumin differentiates the frictional characteristics for x-UHMWPE with different oxidation levels. A model, describing that the properties of the lubricating molecules and articulating surfaces may affect the adsorption of the boundary lubrication thin film which is critical to the tribological behavior, is proposed. (C) 2007 Elsevier B.V. All rights reserved.
Subjects
UHMWPE
albumin
friction
conformation