Surface passivation using oligo(ethylene glycol) in ATRP-assisted DNA detection

We recently reported a DNA sensing method using polymerization to amplify signal outputs [X. Lou, M.S. Lewis, C.B. Gorman, L. He, Anal. Chem. 77 (2005) 4698–4705]. In the current report an optimization of sensor surface chemistry is conducted in which (S–CH2CH2–OEG6–OMe)2 is used as the preferred surface passivation agent to reduce nonspecific adsorption experienced during ATRP-assisted DNA detection. The presence of oligo(ethylene glycol) (OEG) moieties on the sensor surface significantly reduces background adsorption of proteins, polymers, and reaction monomers used during DNA detection. The level of reduction in background nonspecific adsorption closely depends on the incubation solvent and the incubation time used, as evidenced by the ellipsometric and surface plasmon resonance (SPR) results. Reflectance FTIR results suggest that the surfaces with moderately ordered SAMs exhibit better protein resistance, consistent to the previous observations. Subsequent DNA binding experiments show no apparent decrease in DNA hybridization and ligation efficiencies when OEGylated self-assembled monolayers are used as the passivation layer. Improved DNA detection sensitivity is achieved from reduced background noises.