AVS 50th International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI+SS-WeA

Paper BI+SS-WeA10
Immobilization of Oriented Protein Molecules on High-density Poly(ethylene glycol) Coated Si(111)

Wednesday, November 5, 2003, 5:00 pm, Room 307

Session: Biomolecular Surface Science and Microfluidics
Presenter: T. Cha, University of Minnesota
Authors: T. Cha, University of Minnesota
A. Guo, MicroSurfaces, Inc.
X.-Y. Zhu, University of Minnesota
Correspondent: Click to Email
The success of DNA microarray technology has motivated the development of similar tools for proteins. One of the key challenges in this chip-based assay is how the liquid-solid interface is engineered to minimize nonspecific adsorption, to control protein conformation and orientation, and to present high specificity for protein attachment. We demonstrate the synthesis of high density poly(ethylene glycol)-coated Si(111) and its application as an excellent substrate for protein microarray technology. The surface is obtained from the reaction of a multi(8)-armed PEG (mPEG) molecule with a chlorine terminated Si(111) surface to give a PEG film with thickness of 5.2 nm. Four out of the eight arms on each immobilized PEG molecule are accessible for linking to the chelating iminodiacetic acid (IDA) group which binds Cu2+ ions (2.7x10^13/cm2). The resulting Cu2+-IDA-mPEG-Si(111) surface is shown to specifically bind 6x-histidine-tagged protein molecules, including green fluorescent protein and sulfotransferase, without the need of pre-purification. In the case of 6xHis-GFP, this immobilization strategy can lead to a closely packed monolayer of protein molecules. Background tests show that the surface retains its inertness towards non-specific protein adsorption in the absence of either a poly-His tag on the protein molecule or metal ions on the surface. Both the inertness of the chemical surrounding and the controlled orientation contribute to an ideal environment for the immobilized protein molecule to retain its native conformation and reactivity. Enzyme activity for surface immobilized sulfotransferase are measured and compared to solution phase values. Such a kinetic experiment essentially extends a 2-dimensional array to the third dimension-time.