Arylsilanated SiOx Surfaces for Mild and Simple Two-Step Click Functionalization with Small Molecules and Oligonucleotides

The conversion of surface-bound aminophenyl groups to azidophenyl moieties on SiOx surfaces was investigated as part of a mild, simple two-step strategy for "click"-based" surface functionalization with acetylene-functionalized reagents. Small terminal alkynes (phenylacetylene, 1-hexyne) and acetylene-modified single-stranded DNA 20-mers (T-20) were then used as model compounds to test the efficiency of the 1,3-dipolar cycloaddition reaction. The identities of surface species were verified, and their coverages were quantified using X-ray photoelectron spectroscopy in the C 1s, N 1s, F 1s, Cl 2p, and P 2p regions. Depending on conditions, the yield of the azidification was in the 30-90% range, and the efficiency of triazole formation depended significantly on the rigidity of the acetylene reactant. Vibrational sum frequency generation was applied to probe the C-H stretching region and test the platform's viability for minimizing spectral interference in the C-H stretching region. Fluorescence spectroscopy was also performed to verify the presence of fluorescein-tagged DNA single strands that have been coupled to the surface, while label-free DNA hybridization studies by vibrational sum frequency generation spectroscopy readily show the occurrence of duplex formation. Our results suggest that the two-step azidification-click sequence is a viable strategy for readily functionalizing silica and glass surfaces with molecules spanning a wide range of chemical complexity, including biopolymers.