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Sensors 2008, 8(11), 6791-6809; doi:10.3390/s8116791
Article

An Electrochemical DNA Biosensor Developed on a Nanocomposite Platform of Gold and Poly(propyleneimine) Dendrimer

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SensorLab, Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa
* Author to whom correspondence should be addressed.
Received: 29 September 2008 / Revised: 22 October 2008 / Accepted: 27 October 2008 / Published: 1 November 2008
(This article belongs to the Special Issue Dendritic Sensors: From Dendrimer Molecules to Dendritic Cells)
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Abstract

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)63-/4-) redox probe, decreased by 81% compared to bare GCE. The conductivity (in PBS) and reduced Rct (in Fe(CN)63-/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)63-/4- redox probe.
Keywords: Poly(propyleneimine) dendrimer; gold nanoparticle; electrochemical impedance spectroscopy; electrochemical DNA biosensor; DNA Poly(propyleneimine) dendrimer; gold nanoparticle; electrochemical impedance spectroscopy; electrochemical DNA biosensor; DNA
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Arotiba, O.; Owino, J.; Songa, E.; Hendricks, N.; Waryo, T.; Jahed, N.; Baker, P.; Iwuoha, E. An Electrochemical DNA Biosensor Developed on a Nanocomposite Platform of Gold and Poly(propyleneimine) Dendrimer. Sensors 2008, 8, 6791-6809.

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