A tetrafluorophenyl activated ester self-assembled monolayer for the immobilization of amine-modified oligonucleotides

A tetrafluorophenyl (TFP) ester-terminated self-assembled monolayer (SAM) for the fabrication of DNA arrays on gold surfaces is described. Activated ester SAMs are desirable for biomolecule array fabrication because they readily react with amine-containing molecules to form a stable amide linkage. N-Hydroxysuccinimide (NHS) ester SAMs are commonly used for this purpose but are subject to a competing hydrolysis side reaction, limiting their effectiveness under basic conditions. TFP was evaluated here as an alternative activated ester leaving group with a potentially greater stability under basic conditions. It is shown that TFP SAMs are much more stable to basic pH than their NHS analogs and are also more hydrophobic, which is an advantage in the fabrication of high-density spotted arrays. DNA arrays prepared on TFP SAMs at pH 10 have a 5-fold greater surface density of DNA molecules, reduced fluorescence background, and smaller spot radii than those prepared on NHS SAM analogs.