An electrochemical DNA biosensor developed on a nanocomposite platform of gold and poly(propyleneimine) dendrimer
Date
2008Author
Arotiba, Omotayo A.
Owino, Joseph
Songa, Everlyne
Hendricks, Nicolette
Waryo, Tesfaye T.
Jahed, Nazeem
Baker, Priscilla
Iwuoha, Emmanuel I.
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Show full item recordAbstract
An electrochemical DNA nanobiosensor was prepared by immobilization of a
20mer thiolated probe DNA on electro-deposited generation 4 (G4) poly(propyleneimine)
dendrimer (PPI) doped with gold nanoparticles (AuNP) as platform, on a glassy carbon
electrode (GCE). Field emission scanning electron microscopy results confirmed the codeposition
of PPI (which was linked to the carbon electrode surface by C-N covalent bonds)
and AuNP ca 60 nm. Voltammetric interrogations showed that the platform (GCE/PPI-AuNP)
was conducting and exhibited reversible electrochemistry (E°′ = 235 mV) in pH 7.2 phosphate
buffer saline solution (PBS) due to the PPI component. The redox chemistry of PPI was pH
dependent and involves a two electron, one proton process, as interpreted from a 28 mV/pH
value obtained from pH studies. The charge transfer resistance (Rct) from the electrochemical
impedance spectroscopy (EIS) profiles of GCE/PPI-AuNP monitored with ferro/ferricyanide
(Fe(CN)6
3-/4-) redox probe, decreased by 81% compared to bare GCE. The conductivity (in
PBS) and reduced Rct (in Fe(CN)6
3-/4-) values confirmed PPI-AuNP as a suitable electron
transfer mediator platform for voltammetric and impedimetric DNA biosensor. The DNA probe was effectively wired onto the GCE/PPI-AuNP via Au-S linkage and electrostatic
interactions. The nanobiosensor responses to target DNA which gave a dynamic linear range
of 0.01 - 5 nM in PBS was based on the changes in Rct values using Fe(CN)6
3-/4- redox probe.