Browsing by Author "Hawumba, Joseph F."

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    Corrigendum to “Development and Characterization of an Electroless Plated Silver/Cysteine Sensor Platform for the Electrochemical Determination of Aflatoxin B1
    (Journal of Sensors, 2020) Wacoo, Alex Paul; Ocheng, Mathew; Wendiro, Deborah; Vuzi, Peter California; Hawumba, Joseph F.
    Development and Characterization of an Electroless Plated Silver/Cysteine Sensor Platform for the Electrochemical Determination of Aflatoxin B1” [1], anti- Aflatoxin B1-Peroxidase antibody produced in rabbit IgG fraction of antiserum (product number SAB4200829) (Sigma Aldrich, Saint Louis, MO, USA) was mistakenly used as a reagent instead of anti-aflatoxin B1 antibody (product number A8679) (Sigma Aldrich, Saint Louis, MO, USA). Also in the results, Section 3.2 Electrochemical immune detection of aflatoxin B1 the reading was taken from positive potential which was due to impedance measurement. However, this paper is based on the electro-catalytic activity of horseradish peroxidase on the negative potential. In the method Section 2.3, therefore, entry 600nm should be -600 nm. In the result section, the whole of Section 3.2
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    Development and Characterization of an Electroless Plated Silver/Cysteine Sensor Platform for the Electrochemical Determination of Aflatoxin B1
    (Journal of Sensors, 2016) Wacoo, Alex Paul; Ocheng, Mathew; Wendiro, Deborah; California Vuzi, Peter; Hawumba, Joseph F.
    An electroless plated silver/cysteine sensor platform [Glass|silver|cysteine|aflatoxin B1|horseradish peroxidase] for the Electrochemical detection of aflatoxin B1 was developed and characterized. This involved four major steps: (1) an electroless deposition of silver (plating) onto a glass slide, (2) immobilization of cysteine; (3) conjugation of aflatoxin B1 to cysteine groups; and (4) blocking of free cysteine groups with horseradish peroxidase (HRP).The binding of cysteine to the silver was demonstrated by the disappearance of thiol (S-H) groups at 2500 cm−1 using Fourier transmittance infrared spectra (FT-IR), while the subsequent steps in the assembly of sensor platform were monitored using both FT-IR and cyclic voltammetry, respectively. The sensor platform exhibited a broadened nonsymmetrical redox couple as indicated by cyclic voltammetry. The platform was further characterized for sensitivity and limit of detection. The indirect competitive immunoassay format, whereby free and immobilized aflatoxin B1 on the sensor competed for the binding site of free anti-aflatoxin B1 antibody, was used at various concentrations of aflatoxin B1. The sensor generated differential staircase voltammogram that was inversely proportional to the concentration of aflatoxin B1 and aflatoxin B1 in the range of 0.06–1.1 ng/mL with a detection limit of 0.08 ng/mL could be detected.
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    Feasibility of A Novel On‐Site Detection Method for Aflatoxin in Maize Flour from Markets and Selected Households in Kampala, Uganda
    (Toxins, 2018) Wacoo, Alex Paul; Wendiro, Deborah; Nanyonga, Sarah; Hawumba, Joseph F.; Sybesma, Wilbert; Kort, Remco
    In sub-Saharan Africa, there is a high demand for affordable and accessible methods for on-site detection of aflatoxins for appropriate food safety management. In this study, we validated an electrochemical immunosensor device by the on-site detection of 60 maize flour samples from six markets and 72 samples from households in Kampala. The immunosensor was successfully validated with a linear range from 0.7 0.1 to 11 0.3 g/kg and limit of detection (LOD) of 0.7 g/kg. The maize flour samples from the markets had a mean total aflatoxin concentration of 7.6 2.3 g/kg with approximately 20% of the samples higher than 10 g/kg, which is the maximum acceptable level in East Africa. Further down the distribution chain, at the household level, approximately 45% of the total number contained total aflatoxin levels higher than the acceptable limit. The on-site detection method correlated well with the established laboratory-based HPLC and ELISA-detection methods for aflatoxin B1 with the correlation coefficients of 0.94 and 0.98, respectively. This study shows the feasibility of a novel on-site detection method and articulates the severity of aflatoxin contamination in Uganda.
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    Methods for Detection of Aflatoxins in Agricultural Food Crops
    (Journal of applied chemistry, 2014) Wacoo, Alex P.; Wendiro, Deborah; Vuzi, Peter C.; Hawumba, Joseph F.
    Aflatoxins are toxic carcinogenic secondary metabolites produced predominantly by two fungal species: Aspergillus flavus and Aspergillus parasiticus. These fungal species are contaminants of foodstuff as well as feeds and are responsible for aflatoxin contamination of these agro products. The toxicity and potency of aflatoxins make them the primary health hazard as well as responsible for losses associated with contaminations of processed foods and feeds. Determination of aflatoxins concentration in food stuff and feeds is thus very important. However, due to their low concentration in foods and feedstuff, analytical methods for detection and quantification of aflatoxins have to be specific, sensitive, and simple to carry out. Several methods including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), mass spectroscopy, enzyme-linked immune-sorbent assay (ELISA), and electrochemical immunosensor, among others, have been described for detecting and quantifying aflatoxins in foods. Each of these methods has advantages and limitations in aflatoxins analysis.This review critically examines each of the methods used for detection of aflatoxins in foodstuff, highlighting the advantages and limitations of each method. Finally, a way forward for overcoming such obstacles is suggested.