AVS 45th International Symposium
    Biomaterial Interfaces Group Monday Sessions
       Session BI-MoA

Paper BI-MoA10
Characterization of Cellular Interfacial Forces with AFM

Monday, November 2, 1998, 5:00 pm, Room 326

Session: Cell Solid-Surface Interactions
Presenter: T.J. Boland, Pennsylvania State University
Authors: T.J. Boland, Pennsylvania State University
Y.F. Dufrene, Universite Catholique de Louvain, Belgium
W.R. Barger, Naval Research Laboratory
D.L. Allara, Pennsylvania State University
G.U. Lee, Naval Research Laboratory
Correspondent: Click to Email
Biomaterial design depends on understanding the molecular basis of material-body interactions. Much is known about the molecules and cells involved in the body's response to foreign materials but it has been difficult to characterize the physical nature of their interaction. To this end, the interfacial properties of model films have been measured at the nanometer scale with atomic force microscopy (AFM). In specific, as a model for cell surfaces, mixed, uncharged phospholipid/glycolipid monolayers have been deposited on octadecyltrichlorosilane monolayers (OTS) using Langmuir-Blodgett (LB) deposition. The lipid films phase segregate allowing us to measure the relative surface properties of the different phases. Spectroscopic ellipsometry was used to characterize optical properties and thickness of each pure layer and the mixed bilayers in air and in water. As a model for a polymeric surface, AFM probes were functionalized with SH-(CH@sub 2@)@sub 15@-R, where R=CH@sub 3@, CH@sub 2@OH, COOH groups. The height, friction, mechanical properties and surface forces of the lipid phases were measured with these probes. The force curves are purely repulsion due to a dominant short-range force indicative of steric/ hydration interaction and the range of this force is dependent on the head group of the lipid. At high loading forces the probe is observed to snap into contact with the surface which we believe is a measure of the mechanical stability of the film. These measurements demonstrate that AFM can be used to directly characterize molecular interactions between model cell surfaces and model organic surfaces.