AVS 52nd International Symposium
    Applied Surface Science Tuesday Sessions
       Session AS+BI-TuM

Paper AS+BI-TuM11
Studying the Effect of Spacer Thiol Chemistry, Orientation and Surface Coverage on the Hybridization Properties of Mixed DNA SAMs on Gold

Tuesday, November 1, 2005, 11:40 am, Room 206

Session: Surface Characterization of Organic and Biological Systems
Presenter: C.-Y. Lee, University of Washington
Authors: C.-Y. Lee, University of Washington
P. Gong, Colorado State University
H.E. Canavan, University of Washington
L.J. Gamble, University of Washington
D.W. Grainger, Colorado State University
D.G. Castner, University of Washington
Correspondent: Click to Email
Although it is desirable to capture DNA targets without purification from complex milieu (e.g., serum, tissue lysate) for microarray applications, this goal is often hindered by non-specific attachment of DNA and proteins. Minimizing nonspecific adsorption to biosensors and microarrays requires a non-fouling background. Furthermore, the coverage and orientation of DNA probes should be optimized for the capture of low concentrations of DNA via hybridization. To achieve each of these goals, we evaluated the effect that two spacer thiols [11-mercapto-1-undecanol (MCU) and 11-mercapto-undecyl tetra ethylene glycol (OEG)] have on surfaces prepared using singled-stranded DNA containing a thiol anchor group (SH-ssDNA). These mixed DNA self-assembled monolayers (SAMs) have been studied with X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), @super 32@P-radiolabeling, and surface plasmon resonance (SPR). Although XPS and radiolabeling indicate that SH-ssDNA surface coverage steadily decreases with longer exposure to the backfill molecules, NEXAFS indicates that polarization dependence peaks at short MCU and OEG exposure times (< 1h), after which polarization dependence decreases due to the loss of DNA from the surface. A comparison of hybridization responses from these probe surfaces was made using SPR by exposing the surfaces to complementary DNA in various concentrations of serum. SPR results indicate that although surfaces with MCU and OEG thiol spacers showed resistance towards non-specific DNA binding in pure buffer, hybridization efficiency is hindered by non-specific serum protein adsorption even at minimal serum concentration of 1%. Finally, differences in the hybridization property and protein resistance of the SH-ssDNA/MCU and SH-ssDNA/OEG mixed monolayer surfaces will be discussed.