AVS 45th International Symposium
    Biomaterial Interfaces Group Tuesday Sessions
       Session BI-TuM

Invited Paper BI-TuM3
Interaction of Lipid Vesicles and Cell Membranes with Alkylthiol Monolayers

Tuesday, November 3, 1998, 9:00 am, Room 326

Session: Biosensor-Biology Interface
Presenter: A.L. Plant, National Institute of Standards and Technology
Authors: A.L. Plant, National Institute of Standards and Technology
V. Silin, Georgetown University
Correspondent: Click to Email
Surface plasmon resonance (SPR) studies provide real-time information about the nature of the interaction of phospholipid vesicles and red blood cell ghosts with alkylthiol modified surfaces. By using a focussed beam, a range of incident angles are detected simultaneously at a linear CCD array, and the reflectivity response is evaluated at each time point. With this approach it is possible to observe time-dependent changes in the width of the reflectivity response as well as in the angular dependence of the reflectivity minimum. The width of the reflectivity response is an indicator of surface roughness, and helps to elucidate the details of the surface reaction. At a hydrophobic surface, vesicles disassemble and add a monolayer of lipid to the surface, forming a smooth hybrid bilayer that is a model of a cell membrane. This process occurs with vesicles that are net neutral or carry a net negative charge. The interaction of red blood cell ghosts with the surface results in increases and then decreases in the width of the reflectivity response, presumably as a result of initial binding of the cell membrane particles, and then reorganization of the cell membrane into a discrete layer at the hydrophobic surface. The interaction of vesicles with a charged surface is distinctly different from their interaction at a hydrophobic surface. Instead of addition of a layer of lipid, vesicles apparently remain intact at the charged surface, resulting in a large shift in the angle of minimum reflectivity, and an increased and sustained broadening of the reflectivity response. This broadening reflects heterogeneity in the surface coverage, suggesting the long-term presence of intact vesicles at the surface.