Fabrication of a label-free DNA/graphene based electrochemical DNA hybridisation sensor for product authentication and tracing
Date
2017
Authors
Hlongwane, Gloria Ntombenhle
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Abstract
Poor understanding of the interactions at graphene/DNA interfaces has brought
tremendous limitations to the development of label-free DNA-graphene based
electrochemical/electrical biosensors. The aim of this study was to develop a label-free
DNA/graphene-based electrochemical DNA hybridisation sensor, evaluate and benchmark
its output electronic signal as a function of the effect of DNA on graphene’s electronic
properties. In addition, the study sought to understand the effect of graphene on the nature
of DNA. Herein, results of the investigation of the effects of DNA self-immobilisation and
subsequent DNA hybridisation on the electronic structure of CVD-grown graphene using a
combination of Raman spectroscopy and conductance measurements are presented. A
novel UV-Vis spectroscopy dependent measurement technique for the label-free study of
the interaction between DNA-graphene interfaces during DNA hybridisation on graphene
is reported. Also presented in this work, is a new method of representing electronic events
and DNA conformational changes during DNA detection on graphene from current
voltage measurements. Non-covalent assembly was used to immobilise single-stranded
(ssDNA) probes on CVD-grown graphene. On CVD-grown graphene, Raman peak
frequency shifts, intensities and widths of the G and 2D bands after adsorption of the
ssDNA probe and its hybridisation with complementary and mismatched ssDNA strands
were analysed. The effect of graphene on the structural and conformational changes of
DNA upon hybridisation of the ssDNA on the graphene surface both before and after
hybridisation with complementary and triple-base mismatch DNA targets were
investigated by monitoring UV-Vis absorption peaks at the 200 nm to 300 nm range. The
findings were further confirmed through XRD analysis. Using Riemann approximation
method, the rate at which the energy is transformed (power) was computed from the area
under current-voltage curves.
Description
A thesis submitted in fulfilment of the requirements for the
Degree of Doctor of Philosophy,to the Faculty of Engineering and Built Environment, University of the Witwatersrand. Johannesburg, August 2017
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Citation
Hlongwane, Gloria Ntombenhle (2017) Fabrication of a label-free DNA/graphene based electrochemical DNA hybridisation sensor for product authenticating and tracking, University of the Witwatersrand, Johannesburg, https://hdl.handle.net/10539/24969