Please use this identifier to cite or link to this item: https://hdl.handle.net/10321/5452
Title: Development of electrochemical biosensors for sweeteners using engineered nanomaterials supported by computational modelling
Authors: Hloma, Phathisanani 
Keywords: Biosensors;Sweeteners;Nanomaterials;Computational modelling
Issue Date: May-2024
Project: Council of Scientific and Industrial Research (CSIR) 
Abstract: 
Electrochemical immunosensors are a powerful tool in analytical applications. The current
methods for the isolation and detection of artificial and natural sweeteners suffer from
challenges in sample preparation and a lack of specificity. However, electrochemical
immunosensors offer a sensitive, economical, and selective analytical solution to analyse these
commonly used sweeteners, such as aspartame.
The author of this work developed electrochemical immunosensors for the food and beverage
industries to use in the detection and measurement of aspartame, a non-nutritive sweetener, and
rebaudioside A, a natural sweetener. Most artificial sweeteners are low-calorie options that are
suggested for ailments linked to health. These sweeteners' ability to remain stable at even high
temperatures has greatly expanded the range of meals that can use them. Aspartame and
rebaudioside A have not been linked to any health risks, although regulation is still necessary
because of their extensive use in the food industry. The developed immunosensors for the
detection of aspartame and rebaudioside A were achieved and presented as three case studies
in this study.
In the first case study, the immunosensor was achieved by fabricating green synthesized PVP capped silver nanoparticles (PVP-AgNPs) with functionalized multi-walled carbon nanotubes
(fMWCNTs) and immobilizing the human sweet tase receptor T1R2 in a glassy carbon
electrode (GCE), resulting in GCE/PVP-AgNPs/fMWCNTs/T1R2. The electrochemical
assessment of aspartame was achieved using cyclic voltammetry (CV), electrochemical
impedance spectroscopy (EIS), and differential pulse voltammetry (DPV), respectively, under
optimum pH 8 in a 0.1 M phosphate buffer with reference to the Ag/AgCl reference electrode.
The electro-oxidation of ASP was noticed by a well-defined oxidation peak potential at 1.4 V.
The immunosensor sensor showed a linear dynamic range of 2.89 to 27.61 μM (R
2 = 0.9170)
based on differential pulse voltammetry, with limits of detection (LOD) and quantification
(LOQ) (S/N = 3) of 0.40 μM and 1.34 μM, respectively.
The second case study focused on the indirect electrochemical detection of rebaudioside A in
the presence of ferro/ferricyanide as a redox probe. The immunosensor was developed by
fabricating GCE with zeolitic imidazolate framework-67 (ZIF-67) in combination with
fMWCNTs and the immobilization of the T1R2 receptor. The qualitative and quantitative analysis of rebaudioside A was done using CV, EIS, and DPV utilizing a 5 mM [Fe (CN)6]
3-/-4
redox probe. The stable electrode had an exponential dynamic range of 0.9901 µM to 8.2569
µM (R2 = 0.9996). The LOD and LOQ were computed to be 1.10 µM and 3.33 µM,
respectively. This case study also used Patch Dock and PyRx to better understand the
interactions between Reb A and T1R2.
The final case study employed a platinum electrode (PtE) as the working electrode (WE) for
the electrochemical immunosensing of aspartame. The modification of PtE involved the
utilization of a nanocomposite consisting of PVP-AgNPs and reduced graphene oxide (rGO),
with T1R2 immobilized. The electrochemical detection of aspartame was achieved under
optimized conditions at pH 8 in a 0.1 M phosphate buffer, utilizing CV, EIS, and DPV as
electrochemical tools. The PVP-AgNPs/rGO/T1R2 was used to fabricate Pt and the electrode
performed well with a linear increase in oxidation peak currents as aspartame concentrations
were increased from 2.38 µM to 25.78 µM (0.9529). The LOD and LOQ were calculated to be
5.85 µM and 17.73 µM, respectively.
The synthesized nanoparticles and nanocomposites (PVP-AgNPs/fMWCNTs, ZIF 67/fMWCNTs, and PVP-AgNPs/rGO) were characterized using conventional techniques such
as UV-Vis spectroscopy, thermogravimetric analysis (TGA), Fourier transform infrared
spectroscopy (FTIR), field flow fractionation (FFF), single particle inductively coupled plasma
mass spectrometry (sp-ICPMS), energy-dispersive X-ray spectroscopy (EDS), and scanning
electron microscopy (SEM).
In addition to the experimental results, computational chemistry methods were undertaken.
These included adsorption assessments, density functional theory (DFT), and molecular
docking techniques. These techniques were all aimed at achieving a deeper molecular-level
understanding of the interactions among the analytes (Aspartame and Reb A), T1R2, and the
nanocomposites employed in the modification of the working electrodes (GCE and Pt-E)
Description: 
Submitted in fulfilment of the requirements of the degree of Doctor of Philosophy in Chemistry at the Durban
University of Technology, Durban, South Africa, 2024.
URI: https://hdl.handle.net/10321/5452
DOI: https://doi.org/10.51415/10321/5452
Appears in Collections:Theses and dissertations (Applied Sciences)

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