AVS 47th International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI-WeA

Paper BI-WeA6
Modification of Metal Oxide Surfaces for Biosensor and Biomaterial Applications Based on Assembled, Functionalized Poly(L-lysine)-g-poly(ethylene glycol)

Wednesday, October 4, 2000, 3:40 pm, Room 202

Session: Non-fouling Surfaces
Presenter: M. Textor, ETH Zurich, Switzerland
Authors: M. Textor, ETH Zurich, Switzerland
J. Vörös, ETH Zurich, Switzerland
R. Hofer, ETH Zurich, Switzerland
D. Elbert, ETH Zurich, Switzerland
Correspondent: Click to Email
Poly(L-lysine) grafted with poly(ethylene oxide) (PLL-g-PEG) is a polycationic block copolymer that spontaneously assembles as a monolayer at negatively charged metal oxide surfaces such as those formed by titanium oxide, tantalum oxide or niobium oxide. The interaction with the negatively charged surface is shown to be electrostatic through the terminal amine groups of the poly(L-lysine) side chains charged positively at pH below 9. The surfaces have been characterized ex situ using X-ray photoelectron spectrocopy, time-of-flight secondary ion mass spectrometry and reflection-absorption infrared spectroscopy. The planar optical waveguide (grating coupler) technique was used in situ both to monitor in real time the assembly process at the metal oxide waveguide surface, as well as to determine the degree of non-specific adsorption when exposed to serum. The degree of protein resistance was found to depend on the PLL-g-PEG coverage, on the grafting ratio between lysine monomer units and PEG side chains, and on the molecular weight of the PEG used. Using optimized polymer architectures, very low values of serum adsorption could be achieved, typically below the detection limit of our optical waveguide instrument (1 ng/cm2). The surfaces remain protein-resistant in flowing buffer solution at least up to 7 days. Functionalized PLL-g-PEG molecules were synthesized with functional groups such as biotin at the terminal position of the PEG side chains. The functionality of these polymer layers on optical waveguide chips was investigated using a model assay with streptavidin binding, followed by the adsorption of biotinylated recognition units and targeting of proteins such as IgG. This new polymeric interface is shown to have an excellent potential for future applications both in the area of bioaffinity sensor to control specific and non-specific adsorption and for implants such as stents.