Prof. Priscilla Baker
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| Position: | Professor (Analytical Electrochemistry) |
| Department: | Chemistry |
| Faculty: | Faculty of Natural Sciences |
| Qualifications: | BSc (UCT); BSc. Honours (UWC); MSc (UWC); PhD UCT |
| My publications in this repository | |
| More about me: | here |
| Tel: | 021 959 3051 |
| Fax: | 021 959 3055 |
| Email: | pbaker@uwc.ac.za |
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Browsing by Author "Jahed, Nazeem"
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Item An electrochemical DNA biosensor developed on a nanocomposite platform of gold and poly(propyleneimine) dendrimer(MDPI, 2008) Arotiba, Omotayo A.; Owino, Joseph; Songa, Everlyne; Hendricks, Nicolette; Waryo, Tesfaye T.; Jahed, Nazeem; Baker, Priscilla; Iwuoha, Emmanuel I.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.Item Electrochemical immunosensor based on polythionine/gold nanoparticles for the determination of Aflatoxin B1(MDPI, 2008) Owino, Joseph H.O.; Arotiba, Omotayo A.; Hendricks, Nicolette; Songa, Everlyne; Jahed, Nazeem; Waryo, Tesfaye T.; Ngece, Rachel F.; Baker, Priscilla; Iwuoha, Emmanuel I.An aflatoxin B1 (AFB1) electrochemical immunosensor was developed by the immobilisation of aflatoxin B1-bovine serum albumin (AFB1-BSA) conjugate on a polythionine (PTH)/gold nanoparticles (AuNP)-modified glassy carbon electrode (GCE). The surface of the AFB1-BSA conjugate was covered with horseradish peroxidase (HRP), in order to prevent non-specific binding of the immunosensors with ions in the test solution. The AFB1 immunosensor exhibited a quasi-reversible electrochemistry as indicated by a cyclic voltammetric (CV) peak separation (ΔEp) value of 62 mV. The experimental procedure for the detection of AFB1 involved the setting up of a competition between free AFB1 and the immobilised AFB1-BSA conjugate for the binding sites of free anti-aflatoxin B1 (anti-AFB1) antibody. The immunosensor’s differential pulse voltammetry (DPV) responses (peak currents) decreased as the concentration of free AFB1 increased within a dynamic linear range (DLR) of 0.6 - 2.4 ng/mL AFB1 and a limit of detection (LOD) of 0.07 ng/mL AFB1. This immunosensing procedure eliminates the need for enzyme-labeled secondary antibodies normally used in conventional ELISA–based immunosensors.Item Polyester sulphonic acid interstitial nanocomposite platform for peroxide biosensor(MDPI, 2009) Al-Ahmed, Amir; Ndangili, Peter M.; Jahed, Nazeem; Baker, Priscilla; Iwuoha, Emmanuel I.A novel enzyme immobilization platform was prepared on a platinum disk working electrode by polymerizing aniline inside the interstitial pores of polyester sulphonic acid sodium salt (PESA). Scanning electron microscopy study showed the formation of homogeneous sulphonated polyaniline (PANI) nanotubes (~90 nm) and thermogravimetric analysis (TGA) confirmed that the nanotubes were stable up to 230 °C. The PANI:PESA nanocomposite showed a quasi-reversible redox behaviour in phosphate buffer saline. Horseradish peroxidase (HRP) was immobilized on to this modified electrode for hydrogen peroxide detection. The biosensor gave a sensitivity of 1.33 μA (μM)-1 and a detection limit of 0.185 μM for H2O2. Stability experiments showed that the biosensor retained more than 64% of its initial sensitivity over four days of storage at 4 °C.