THESIS
2014
iii leaves, iv-xv, 132 pages : illustrations ; 30 cm
Abstract
Electrochemical biosensing of sequence-specific nucleic acid hybridization offers
unprecedented opportunities for decentralized genetic testing which requires portable,
cost-effective and low-power readout devices and has received considerable attention during
the past decade. To date, most of the electrochemical nucleic acid biosensors that have been
developed are based on heterogeneous assay in which interaction between
surface-immobilized probe and target strand is translated into an informational
electrochemical signal. The achievement of high sensitivity demands laborious optimization
of probe immobilization including the surface chemistry and coverage to maximize
hybridization efficiency and meanwhile minimize non-specific binding/adsorption events.
More importantly, conf...[
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Electrochemical biosensing of sequence-specific nucleic acid hybridization offers
unprecedented opportunities for decentralized genetic testing which requires portable,
cost-effective and low-power readout devices and has received considerable attention during
the past decade. To date, most of the electrochemical nucleic acid biosensors that have been
developed are based on heterogeneous assay in which interaction between
surface-immobilized probe and target strand is translated into an informational
electrochemical signal. The achievement of high sensitivity demands laborious optimization
of probe immobilization including the surface chemistry and coverage to maximize
hybridization efficiency and meanwhile minimize non-specific binding/adsorption events.
More importantly, configurational freedom of the surface-immobilized probe is restrained,
resulting in reduced hybridization kinetics and specificity compared to fluorescent nucleic acid assays which are normally homogenous. Recently, our group developed an
immobilization-free detection approach which requires no probe immobilization step and
solves the fore-mentioned issues. However, the sensitivity of this method is relatively low due
to its diffusion-controlled nature.
In this thesis work, we developed a group of ultrasensitive immobilization-free
electrochemical DNA biosensors based on enzyme-assisted and enzyme-free signal
amplification strategy. These sensors utilize the catalytic activity of different DNA enzymes
and kinetically-controlled DNA assembly reaction to achieve linearly or even exponentially
amplified electrochemical signal. Competitive detection limits as well as ultrahigh selectivity
to distinguish even single base mismatches have been demonstrated with these presented
sensors, which could be a promising alternative to the conventional electrochemical
biosensors for developing portable and cost-effective DNA sensing devices.
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