title: An Electrochemical DNA Biosensor Developed on a Nanocomposite Platform of Gold and Poly(propyleneimine) Dendrimer.
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.
authors.affiliation: SensorLab, Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa. oarotiba@uwc.ac.za.
authors.forename: Omotayo
authors.initials: O
authors.lastname: Arotiba
authors.affiliation: SensorLab, Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa. jowino@uwc.ac.za.
authors.forename: Joseph
authors.initials: J
authors.lastname: Owino
authors.affiliation: SensorLab, Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa. esonga@uwc.a.za.
authors.forename: Everlyne
authors.initials: E
authors.lastname: Songa
authors.affiliation: SensorLab, Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa. nhendricks@uwc.ac.za.
authors.forename: Nicolette
authors.initials: N
authors.lastname: Hendricks
authors.affiliation: SensorLab, Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa. twaryo@uwc.ac.za.
authors.forename: Tesfaye
authors.initials: T
authors.lastname: Waryo
authors.affiliation: SensorLab, Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa. njahed@uwc.ac.za.
authors.forename: Nazeem
authors.initials: N
authors.lastname: Jahed
authors.affiliation: SensorLab, Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa. pbaker@uwc.ac.za.
authors.forename: Priscilla
authors.initials: P
authors.lastname: Baker
authors.affiliation: SensorLab, Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa. eiwuoha@uwc.ac.za.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Iwuoha
keywords: DNA; Poly(propyleneimine) dendrimer; electrochemical DNA biosensor; electrochemical impedance spectroscopy; gold nanoparticle