Browsing by Author "Rassie, Candice"

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    Application on gold nanoparticles-dotted 4-nitrophenylazo graphene in a label-free impedimetric deoxynivalenol immunosensor
    (MDPI, 2015) Sunday, Christopher Edozie; Masikini, Malua; Wilson, Lindsay; Rassie, Candice; Waryo, Tesfaye T.; Baker, Priscilla; Iwuoha, Emmanuel I.
    In this paper, we report a new concept to construct a label-free electrochemical inhibition-based immunosensor for the detection of the mycotoxin deoxynivalenol (DON) in cereal samples. The electrochemical impedance spectroscopy of tris(bipyridine) ruthenium (II) chloride was used as a marker enhanced with gold nanoparticles-dotted 4-nitrophenylazo functionalized graphene (AuNp/G/PhNO2) nanocatalyst mediated in Nafion on a glassy carbon electrode. Under the optimized conditions, the formation of immunocomplexes inhibited electron flow and increased the charge transfer resistance of the sensing interface linearly. The change in impedance was proportional to DON concentrations in the range of 6–30 ng/mL with a sensitivity and detection limit of 32.14 ΩL/ng and 0.3 µg/mL, respectively, which compares favorably with the ELISA result. The proposed sensor had a stability of 80.3%, good precision and selectivity in DON standard solution containing different interfering agents, indicating promising application prospect for this strategy in designing impedimetric, electrochemiluminescent, voltammetric or amperometric sensors.
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    Electrochemical cytochrome P450 enzymatic biosensors for the determination of the reactivity of TB drugs
    (University of Western Cape, 2020) Rassie, Candice; Iwuoha, Emmanuel; Ajayi, Fanelwa
    Tuberculosis (TB) remains a global epidemic despite the fact that treatment has been available since the 1950’s. This disease is highly contagious and spreads via transmission of the Mycobacterium Tuberculosis (MTB) tubercle via coughing, sneezing and spitting. The disease has various side effects including weight loss, fatigue and even death. To date no cure has been found for TB and thus optimisation of treatment is a constant focus in health related research. TB is highly prevalent in South Africa due to the increased level of patients who are co-infected with HIV. Treatment for TB consists of first line drugs including isoniazid (INH), ethambutol (ETH), pyrazinamide (PYR) and rifampicin (RIF). These drugs are highly effective but also produce many adverse drug reactions (ADR’s) over the 6-month course of treatment. These reactions lead to patients not completing the course, losing quality of life and ultimately adding to the development of drug resistant strains of TB. A method of minimising these ADR’s is the development of a phenotype sensor, which is able to determine the metabolic profile of patients. Metabolic profiles play a huge role in the efficacy of treatment by tailoring treatment in order for patients to stay within the therapeutic range of treatment. This would in turn minimise both toxicity and ineffective treatment. Various methods for the quantification of drugs have been developed such as high performance liquid chromatography (HPLC), mass spectrometry (MS) and ultra-violet visible spectroscopy (UV-vis).
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    Optimisation of a microfluidic device for the pre-concentration and size separation of cell free foetal DNA from maternal plasma by capillary electrophoresis
    (University of the Western Cape, 2012) Rassie, Candice; Iwuoha, Emmanuel; O’Sullivan, Ciarra
    The discovery of cell free foetal DNA (cffDNA) in 1997 allows for the combination of accuracy as well as non-invasiveness for prenatal diagnosis. This non-invasive genetic test requires only a maternal blood sample from which the cffDNA can be isolated and analysed. In this work cffDNA was isolated from a maternal blood sample using a micro-fluidic device which was fabricated using hot embossing and laser ablation techniques. The DNA sample was first pre-concentration by electrokinetic trapping (EKT) and then isotachophoresis (ITP). The concentrated sample was then separated by size using capillary electrophoresis (CE), all in a single device. All parameters and processes concerned with the micro-fluidic device were optimised sequentially. These parameters include both the chemical components as well as the physical processes which occur. The DNA used for the optimisation protocol was analysed using fluorescence spectroscopy, agarose gel electrophoresis as well as an Agilent Bioanalyser. The optimised protocol included a 9% acrylamide/pDMA matrix, 3 M N,N-dimethylurea as a denaturing agent, with tris based buffers for pre-concentration steps and 1X TBE (tris/borate/EDTA) buffer for capillary electrophoresis. The applied voltage of ITP was 300 V and CE was carried out at 180 V. The timing at which DNA was extracted from the device was kept at time = 60 s intervals. The optimised protocol was then used for real sample analysis and these samples were obtained from mothers pregnant with male foetuses. The DNA extracted from the micro-fluidic device was then analysed using real time PCR (RT-PCR) in order to distinguish which was maternal and which was foetal. This was carried out by amplification of male and general (present in male and female) genes respectively. RT-PCR results confirmed that only the male specific gene was amplified in initial samples exiting the device and it was thus successful in isolating cffDNA from a maternal plasma sample.