Genosensing of CP4EPSPS DNA segment in genetically modified cereal using luminescent CdSe quantum dots.
Date
2025
Authors
Mabo, Happy
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Zambia
Abstract
A cadmium selenide quantum dot (CdSe-QDs) based genosensor for the detection of the CP4 epsps DNA segment of 5-Enolpyruvylshikimate-3-Phosphate Synthase (CP4 EPSPS) in Genetically Modified Cereal was developed. The efficacy of the CdSe-QDs synthesized from cadmium chloride (CdCl2) and selenium powder (Se) with polyvinyl alcohol (PVA) as a stabilizer was investigated. The QDs were characterised using UV-Vis for film thickness which affects the band gap energy and particle size and Fourier transform infrared spectrophotometry (FT-IR) for functional group analysis and potentiometric tests for determination of signal transduction and limit of detection. The UV-Vis results for the QDs showed a peak of 485 nm with an absorption edge towards 600 nm, which is attributed to the quantum confinement effect. The band gap for the QDs was found to be 3.43 electron Volts (eV) and the average diameter size was 2.82 nm, indicating the successful formation of quantized particles with very high luminescence and this was supported by the shorter absorption wavelength of the particles in the fluorescence measurements obtained. The surface modified and functionalised CdSe QDs gave a maximum binding capacity, Qm, value of 0.0108 mg/g, and an R2 = 0.99902 for the Langmuir and R2 = 0.81190 for the Freundlich isotherms, indicating that the data fitted better in the Langmuir isotherm model. The FT-IR results showed characteristic absorption bands for thiourea, glutaraldehyde and the immobilized oligonucleotides indicating successful modification of the QDs. In this research the DNA containing samples were qualitatively and quantitatively determined potentiometrically yielding the following results: 92.2% (forward sample, F), 4.1% (reverse sample, R), 76.5% (positive control sample, +ve), 5.4% (negative control sample, -ve), 3.4% (cereal A sample) and 57.9% (cereal B sample) hybridizations. These results indicate that this designed method of detection based on CdSe QDs may actually work as a rapid detection method for GM soyabeans and corn, both qualitatively and quantitatively, and had a very low detection limit of 2.42 × 10-5 ng L-1.
Description
Thesis of Master of Science in Chemistry.