AVS 50th International Symposium
    Applied Surface Science Tuesday Sessions
       Session AS+BI-TuA

Paper AS+BI-TuA4
Base-dependent Displacement of Thiolated DNA Films by Mercaptohexanol (MCH)

Tuesday, November 4, 2003, 3:00 pm, Room 324/325

Session: Biomaterials Characterization
Presenter: H. Kimura-Suda, National Institute of Standards and Technology
Authors: H. Kimura-Suda, National Institute of Standards and Technology
D.Y. Petrovykh, University of Maryland & Naval Research Laboratory
L.J. Whitman, Naval Research Laboratory
M. Tarlov, National Institute of Standards and Technology
Correspondent: Click to Email
The immobilization of DNA on surfaces is the basis for DNA microarrays and many emerging nanotechnology applications. It has been demonstrated that the attachment of thiolated DNA probes to gold surfaces is an effective approach for construction of DNA-based sensors and diagnostics. One challenge with the use of thiolated DNA is reproducibly controlling the surface coverage and hybridization activity of adsorbed probes. A two-step method, where first the gold substrate is exposed to a solution of thiol-modified single-stranded DNA (HS-DNA), followed by exposure to a solution of mercaptohexanol (MCH), is a common approach for controlling the coverage and orientation of DNA probes. In this protocol, MCH both passivates the surface against nonspecific adsorption of DNA targets and "activates" DNA probes by displacing adsorbed nucleotides from the gold surface. The MCH treatment also displaces DNA probes from the gold surface resulting in less steric hindrance for hybridization. Nonetheless, the displacement of thiolated DNA by MCH remains poorly understood. In this study, we focused on base-dependent displacement of HS-DNA films from gold upon MCH exposure. Self-assembled monolayers of thiolated homo-oligonucleotides [HS-(dA), HS-(dT), HS-(dC), HS-(dG)] on gold surfaces were produced and characterized before and after exposure to MCH with FTIR and XPS. Surprisingly, we find that the displacement of HS-DNA on gold by MCH is strongly base-dependent. For example, most HS-(dT) is removed or displaced, whereas most HS-(dC) remains on the surface. In this talk we will present a selectivity series for the base dependent displacement of homo-oligonucleotides by MCH and discuss the origin of this effect. We will demonstrate that base dependent displacement effects can account for dramatic variations in probe coverage for probes of different base composition.