5‘-Thiolated Oligonucleotides on (3-Mercaptopropyl)trimethoxysilane−Mica: Surface Topography and Coverage

Abstract

DNA (deoxyribonucleic acid) microarrays are used as a tool in high-throughput methods to obtain genetic information. Using atomic force microscopy, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry, and confocal scanning fluorescence microscopy, we investigated how the surface properties and topography of (3-mercaptopropyl)trimethoxysilane (MPTS)-coated mica influence the immobilization of 5‘-thiolated oligonucleotides. Mica surfaces were grafted with concentrations of MPTS varied over 3 orders of magnitude (5.38 mM to 5.38 M). At low concentration (5.38 mM), condensed MPTS appeared to form “island-like” structures with an average surface area of 100 nm2. The MPTS islands grew in size to 2400 nm2 as the concentration of MPTS was increased, suggesting the formation of an MPTS monolayer. XPS analysis indicated a corresponding increase in the elemental concentration of sulfur. At high MPTS concentrations (107.6 mM and 5.38 M), the island structures disappeared, suggesting...