Sibulelo Vilakazi

The effects of carbon nanotubes on the electrocatalysis of hydrogen peroxide by metallo-phthalocyanines.

The pre-grafted screen-printed gold electrode modified with phenyl-amino monolayer was investigated for covalent immobilization of phenyl-amine functionalized single-walled carbon nanotubes (PA-SWCNT) and metal tetra-amino phthalocyanine (MTAPc) using Schiff-base reactions with benzene-1,4-dicarbaldehyde (BDCA) as cross-linker. The PA-SWCNT and MTAPc modified electrodes were applied as hybrids for electrochemical sensing of H(2)O(2). The step-by-step fabrication of the electrode was followed using electrochemistry, impedance spectroscopy, scanning electron microscopy and Raman spectroscopy and all these techniques confirmed the fabrication and the immobilization of PA-SWCNT, MnTAPc and CoTAPc onto gold surfaces. The apparent electron transfer constant (k(app)) showed that the carbon nanotubes and metallo-phthalocyanines hybrids possess good electron transfer properties compared to the bare, pre-grafted and the MTAPc modified gold electrode surfaces without PA-SWCNT. The electrochemical sensing of hydrogen peroxide was successful with PA-SWCNT-MTAPc hybrid systems showing higher electrocatalytic currents compared to the other electrodes. The analytical parameters obtained using chronoamperometry gave good linearity at H(2)O(2) concentrations ranging from 1.0 to 30.0 μmol L(-1). The values for the limit of detection (LoD) were found to be of the orders of 10(-7)M using the 3δ for all the electrodes. The PA-SWCNT-MTAPc modified SPAuEs were much more sensitive compared to PA-MTAPc modified SPAuEs.

Electrochemical impedimetric immunosensor for the detection of measles-specific IgG antibodies after measles infections

The detection of measles-specific primary antibodies (IgG) using electrochemical impedimetric immunosensors is reported. The optimum conditions for electrode saturation were reached after 40 min for 1 μg ml(-1) antibody concentrations. Surface roughness using AFM increased with each immobilization or antigen-antibody reaction step clearly confirming the surface modification and recognition between antigen and antibody. The human serum (HS) and new-born calf serum (NCS) spiked with antigen-specific antibody were studied to mimic the real sample analysis. The HS and NCS sera containing antibodies due to measles exhibited correlation between the increasing antibody serum concentrations and the charge-transfer resistance (electrochemically measured). This work clearly showed the potential use of impedance as the preferred electrochemical method for detecting measles-antibodies in label-free manner.

Nanostructured metallophthalocyanine complexes: synthesis and electrocatalysis

In this review, we have attempted to summarize the synthesis and catalytic applications of the nanophthalocyanine complexes. In cases where possible, we have compared the catalytic activity of the nanophthalocyanines to the bulk material. Catalytic detection of dopamine, epinephrine, glucose and some pollutants using nanostructured metallophthalocyanine have been covered.

Metallophthalocyanines and metalloporphyrins as electrocatalysts: a case of hydrogen peroxide and glucose detection

This review summarizes the applications of metallophthalocyanine (MPc) and metallo-porphyrin (MP) complexes as electrocatalysts immobilized onto various electrodes for the detection of hydrogen peroxide and glucose. The uses of MPc and MP complexes as electron mediators for the detection of glucose at glucose oxidase modified surfaces are discussed.

Electrocatalytic behavior of cobalt phthalocyanine complexes immobilized on glassy carbon electrode towards the reduction of dicrotophos pesticide

Electrocatalytic properties of cobalt phthalocyanine (CoPc), cobalt tetra-carboxy phthalocyanine (CoTCPc) and cobalt octa-carboxy (CoOCPc), towards the detection of dicrotophos have been studied. Catalytic behavior towards the reduction of dicrotophos was found to be dependent on the pH, as well as the substitution on the phthalocyanine ring. Strong electron withdrawing groups on the phthalocyanine ring yielded best catalysis as evidenced by the enhancement of the reduction peak current, (~5 fold) compared to the bare glassy carbon electrode. The analysis gave a good detection limit of 1.25 × 10-7 M, and good linearity for the studied concentration range. A high Tafel slope value was obtained, indicating a strong interaction between dicrotophos and the cobalt phthalocyanine complex.

Polyanilino-Carbon Nanotubes Derivatised Cytochrome P450 2E1 Nanobiosensor for the Determination of Pyrazinamide Anti-Tuberculosis Drugs

Pyrazinamine (PZA) is one of the most commonly prescribed anti-tuberculosis (anti-TB) drug due to its ability to significantly shorten the TB treatment period. However, excess PZA in the body causes hepatotoxicity and liver damage. This, therefore, calls for new methods for ensuring reliable dosing of the drug, which will differ from person to person due to interindividual differences in drug metabolism. A novel biosensor system for monitoring the metabolism of PZA was prepared with nanocomposite of multi-walled carbon nanotubes (MWCNTs), polyaniline (PANI) and cytochrome P450 3A4 (CYP3A4) electrochemically deposited on a glassy carbon electrode (GCE). The nanocomposite biosensor system exhibited enhanced electroactivity that is attributable to the catalytic effect of the incorporated MWCNTs. The biosensor had a sensitivity of 7.80 μA/μg mL-1 PZA and a dynamic linear range of 4.92 160 ng/mL PZA.

Design and evaluation of an electrochemical immunosensor for measles serodiagnosis using measles-specific Immunoglobulin G antibodies.

The design of electrochemical immunosensors for the detection of measles-specific antibodies is reported. The measles-antigen modified surface was used as an antibody capture surface. The detection of measles-specific IgG antibodies was accomplished using the voltammetric method and horse-radish peroxidase (HRP) labeled secondary antibody (anti-IgG) as a detecting antibody. The potential applications of the designed immunosensor were evaluated in buffer and serum solutions. The immunosensor exhibited good linearity at concentrations less than 100 ng mL(-1) with R(2)=0.997 and the limit of detection of 6.60 ng mL(-1) at 3σ. The potential application of the immunosensor was evaluated in the deliberately infected human and newborn calf serum samples with measles-IgG antibody mimicking real-life samples. The designed electrochemical immunosensor could differentiate between infected and un-infected serum samples as higher catalytic currents were obtained for infected serum samples.