Effect of short chain alkane diluents on the label free electrochemical DNA hybridization discrimination at the HS-ssDNA/diluent binary mixed monolayer in presence of cationic intercalators

Influence of short chain alkane diluents (number of carbons, n= 2, 3 and 6) on the control of non-specific DNA-gold (DNA-Au) interactions nd hybridization discrimination effect has been investigated at the binary monolayer interface consisting of 6-mercapto-1-hexane labeled single tranded DNA (HS-ssDNA) and a diluent (HS-ssDNA/diluent) in presence of double stranded DNA (dsDNA) specific cationic intercalators nd [Fe(CN)6]3−. The diluents used are 1-mercaptopropane (MP), 3-mercaptopropionic acid (MPA), Cystamine, 1-mercapto ethanol (MCE) and -mercapto-1-hexanol (MCH). Label free electrochemical DNA hybridization discrimination of the complementary hybrid (hybridized) and nonomplementary (un-hybridized) surfaces has been made comparatively in presence of the [Fe(CN)6]3− and dsDNA specific intercalators, such as roflavine and methylene blue. Prior to the target hybridization, the control of non-specific DNA-Au interaction is interrogated by monitoring he integrity of the HS-ssDNA monolayer in presence of the [Fe(CN)6]3− before and after the HS-ssDNA/diluent binary interface formation. hange in the peak-to-peak separation ( Ep), taken as a measure of the control of the non-specific DNA-Au interactions, follows the order P < MCH < MPA. But the hybridization discrimination effect, measured as the difference in the total charge passed through the hybridized nd un-hybridized layer in presence of the Fe(CN)63− and intercalator, follows the reverse order MPA < MCH < MP. These contrasting behaviors re related to the different interactions of hydrophobic and/or hydrophilic diluents with the hydrophobic HS-ssDNA while forming the binary ecognition interface. Reductive desorption voltammetry of these binary interfaces in 0.5 M KOH evidences the formation of highly compact layer n presence of MP and MCH diluents and defective layer in presence of MPA diluent by the difference in their reductive desorption pattern and upports the observed phenomenon. Brain tumor sequence is used as the model system and the lowest target concentration of 100 pM is detected ensitively and selectively at these binary monolayers. 2007 Elsevier B.V. All rights reserved.