AVS 49th International Symposium
    Biomaterials Tuesday Sessions
       Session BI-TuP

Paper BI-TuP11
Comparison of Polystyrene and Teflon-AF as Model Surfaces for Hydrophobic Adsorption and Biocompatibilization

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Biointerfaces and Surfaces I
Presenter: L. Feller, Swiss Federal Institute of Technology
Authors: L. Feller, Swiss Federal Institute of Technology
N. Tirelli, Swiss Federal Institute of Technology
S.M. De Paul, Swiss Federal Institute of Technology
J.P. Bearinger, Swiss Federal Institute of Technology
A. Napoli, Swiss Federal Institute of Technology
J.A. Hubbell, Swiss Federal Institute of Technology
M. Textor, Swiss Federal Institute of Technology
Correspondent: Click to Email
The motivation of this investigation is to produce materials for applications in biosensors and biomedical materials via surface modification based on hydrophobic interactions. For this purpose we have used the physical adsorption of amphiphilic poly(propylene sulfide)-block-poly(ethylene glycol) (PPS-PEG), from a polar solvent (methanol, water). Upon deposition on a hydrophobic surface, these polymers display the biocompatible, protein-repellent PEG as the top layer and are believed to maintain this architecture when placed in either water-based model electrolytes or a physiological environment. We have chosen to apply this method of surface modification to two hydrophobic materials, poly(styrene) and Teflon-AF. These materials have already been used in biomedical applications but which require a surface biocompatibilization to reduce unfavorable foreign-body reactions. Both polymers can be produced in form of thin films (20-50 nm thickness) via spin-coating. We studied the properties of thin films of these two hydrophobic surfaces and their behavior in subsequent PPS-PEG adsorption studies. The thickness and uniformity of spin-coated surfaces are sensitive to rotation speed and concentration. For optical waveguide lightmode spectroscopy (OWLS) investigations it is necessary to have an optically transparent homogenous thin layer of ideally 12 nm thickness. We produced a series of both poly(styrene) and Teflon-AF layers of various thicknesses and characterized their homogeneity and thickness using an Atomic Force Microscope (AFM). Layer stability was characterized by dynamic contact angle measurements. The adsorption of PPS-PEG block copolymers through hydrophobic interactions was subsequently studied by OWLS. PPS-PEG demonstrated good adsorption on both surfaces, showing complete and stable coverage under physiological conditions. Preliminary experiments have also shown that the deposited layers strongly decrease the protein adsorption on such substrates.