Controlling structural properties of self-assembled oligonucleotide-mercaptohexanol monolayers

The achievement of high hybridization efficiency in DNA microarrays is largely affected by the surface density of immobilized functional DNA probes. We investigated the chemical conditions for the formation of mixed self-assembled monolayers of thiol-modified oligonucleotides and mercaptohexanol deposited onto gold surfaces. The surface density of DNA was studied by means of high-resolution X-ray photoemission spectroscopy. The measurements revealed that the spatial density of DNA strands can be controlled within a wide range by the concentration of MgCl2 in the immobilization buffer. Moreover, improved preparation conditions for high-quality self-assembled hybrid monolayers are presented. Compared to our previous work, a reduction in unbound thiol was achieved by changing from ethanolic to aqueous solvent and lowering the MCH concentration.