Graphene-Assisted
Label-Free Homogeneous Electrochemical
Biosensing Strategy based on Aptamer-Switched Bidirectional DNA Polymerization
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Abstract
In this contribution, taking the
discrimination ability of graphene
over single-stranded (ss) DNA/double-stranded (ds) DNA in combination
with the electrochemical impedance transducer, we developed a novel
label-free homogeneous electrochemical biosensor using graphene-modified
glassy carbon electrode (GCE) as the sensing platform. To convert
the specific aptamer-target recognition into ultrasensitive electrochemical
signal output, a novel aptamer-switched bidirectional DNA polymerization
(BDP) strategy, capable of both target recycling and exponential signal
amplification, was compatibly developed in this study. In this strategy,
all the designed DNA structures could be adsorbed on the graphene/GCE
and, thus, serve as the electrochemical impedance signal reporter,
while the target acts as a trigger of this BDP reaction, in which
these designed DNA structures are bound together and, then, converted
to long dsDNA duplex. The distinct difference in electrochemical impedance
spectroscopy between the designed structures and generated long dsDNA
duplex on the graphene/GCE allows label-free and homogeneous detection
of target down to femto-gram level. The target can be displaced from
aptamer through the polymerization to initiate the next recognition–polymerization
cycle. Herein, the design and signaling principle of aptamer-switched
BDP amplification system were elucidated, and the working conditions
were optimized. This method not only provides a universal platform
for electrochemical biosensing but also shows great potential in biological
process researches and clinic diagnostics