AVS 53rd International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI-WeM

Paper BI-WeM9
Characterization of Surface-Immobilized Layers of Intact Liposomes by Atomic Force Microscopy Force Measurements and Quartz Crystal Microbalance

Wednesday, November 15, 2006, 10:40 am, Room 2014

Session: Bio-interfacial Modification and Bio-Immobilization I (Honoring Marcus Textor, ETH-Zürich for Substantial Contributions to the Field)
Presenter: H. Brochu, Université de Sherbrooke, Canada
Authors: H. Brochu, Université de Sherbrooke, Canada
P. Vermette, Université de Sherbrooke, Canada
Correspondent: Click to Email
The scientific literature is abundant on the development, characterization and validation of liposome suspensions, particularly in the biomedical fields. However, much less is known on the surface immobilization of layers of intact liposomes, which can find applications in several fields including drug-partitioning chromatography, cell structure mimicking, and localised drug delivery. In fact, surface-bound liposomes have been validated as localized drug delivery systems in some applications. Although some papers are available on the characterization of surface-immobilized layers of intact liposomes, many physicochemical properties of these complex thin layers still need to be elucidated. Briefly, these surfaces are made using radiofrequency glow discharge deposition to coat a surface with a thin polymeric film bearing amine groups with the subsequent covalent attachment, using carbodiimide chemistry, of NHS-poly(ethylene glycol)-biotin (NHS-PEG-biotin) low-fouling polymer prepared under cloud point conditions. Next, NeutrAvidin (NA) molecules are docked on the PEG layers bearing biotin followed by the attachment of biotinylated liposomes, which anchor to the NA. X-ray photoelectron spectroscopy is used to follow-up the chemical surface modification steps. This talk will present surface characterization of layers of intact liposomes by AFM force measurements and QCM analysis with dissipation monitoring with the aim to develop a model of the mechanical properties of these thin layers. With AFM force measurements, estimation of the Young modulus of these well hydrated layers is obtained using the Hertz model. QCM measurements allowing dissipation monitoring provide some information on the mechanical properties of these surface-bound liposomes. QCM is also used to study the dynamics of protein adsorption on these surface-bound liposomes. Also, kinetics of the sequential release of more than one molecules from these layers of intact liposomes is investigated.