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    Biomaterials Monday Sessions
       Session BI+SS-MoA

Paper BI+SS-MoA5
The Role of Interphase Water in Protein Resistance

Monday, October 29, 2001, 3:20 pm, Room 102

Session: Role of Water in Biological Systems
Presenter: J.G. Kushmerick, Sandia National Laboratories
Authors: J.G. Kushmerick, Sandia National Laboratories
J.E. Houston, Sandia National Laboratories
B.C. Bunker, Sandia National Laboratories
Correspondent: Click to Email
While the inertness of oligo(ethylene glycol) (OEG) terminated self-assembled monolayers (SAMs) towards protein adsorption is well documented, the physical cause for the protein resistance has remained the subject of debate. Steric repulsion, which accounts for the inertness of endgrafted poly(ethylene glycol), is not applicable to thin densely packed OEG-SAMs. A strongly bound water layer templated by the OEG-SAM has been proposed to account for the protein resistance. Interfacial force microscope measurements of the interaction between functionalized probe tips and OEG-SAMs in water reveal a long-range (> 4 nm) repulsion. The repulsion is consistent with the existence of a thick interphase water layer with an elastic modulus similar to that of ice. Such an interphase layer, which is consistent with theoretical calculations and neutron reflectivity data, could account for the protein resistance of OEG-SAMs. Experiments aimed to further understand the mechanical properties of the water interphase, including varying the metal substrate, variable temperature and quartz crystal microbalance measurements, will also be discussed. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the US Department of Energy.