9 Aptamers for the Diagnosis of Malign Tumors
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or photo-electrochemical biosensors, surface plasmon resonance, surface-enhanced
Raman scattering, fluorescence energy transfer, and colorimetric-based platform.
These so-called aptasensors can meet the needs for fast, convenient, and portable
molecular devices.
9.3.1 Electrochemical Aptasensors
Electrochemical aptasensors contains a surfaced functional electrode as the platform for biological sensing aptamer immobilization. The electrochemical current
variations can monitor the analyte-binding event, which can be used for analyte
detection. Electrochemical transduction can be achieved through many approaches,
such as impedimetric, potentiometric, amperometric, and photo-electrochemical.
The electrochemical aptasensors can offer several advantages, as readily miniaturized, low cost of production without expensive optical instruments, and especially
high sensitivity, which can approach the clinical testing requirements. And also, these
aptamer-based electrochemical platforms can be label-free and reusable, promising
for real-time monitoring.
The vascular endothelial growth factor (VEGF) is a regulator for vascular permeabilization and angiogenesis, and the most abundant and potent isoform, VEGF 165 ,
has been identified as cancer biomarkers [33]. The electrochemical biosensor should
construct with the aptamer as a recognition element and a catalytic redox reaction must happen to transfer electrons to the electrode [34]. Qureshi et al designed
an on-chip aptamer-antibody sandwich-type electrochemical biosensor for VEGF
protein sensing, using the gold microelectrodes arrays. The aptamer-VEGF protein
complex was then captured by antibody-coated magnetic beads, resulting in the
change in capacitance and impedance. The capacitance change was quantified by
non-Faradaic electrochemical impedance spectroscopy (nFIS) [35]. Carbon or metal
nanomaterials are used for electrochemical aptasensor establishment, and the surface
modification could enhance the electrical signal [36]. Another research reported an
ultra-traceVEGF 165 -sensing aptasensor based on the nanocomposite platform (BSAAuNCs/IL) functional glassy carbon electrode for aptamers immobilization. The
VEGF binding could cause a decrease of differential pulse voltammetry current
together with more mass-transfer limiting to the electrode surface. The benefit of the
large surface area of gold-nanocluster for VEGF immobilization, more this sensor
could achieve the detection range of 2.5–250 pM with limit of detection (LOD)
of 0.48 pM [37]. By utilization the ordered mesoporous carbon-gold nanocomposites (OMCeAu-NCs)modified screen-printed electrode to immobilize the VEGF
aptamers, the electrochemical sensor could detect VEGF in serum range from 10.0
to 300.0 pg/mL with LOD of 1.0 pg/mL using cyclic voltammetry along with electrochemical impedance spectroscopy [38]. A sandwich electrochemical aptasensor
based on graphite screen-printed electrodes was established with thiolated DNA
aptamer and secondary biotinylated aptamer. This strategy showed the LOD of
30 nmol/L by means of differential pulse voltammetry (DPV) [39].
245
or photo-electrochemical biosensors, surface plasmon resonance, surface-enhanced
Raman scattering, fluorescence energy transfer, and colorimetric-based platform.
These so-called aptasensors can meet the needs for fast, convenient, and portable
molecular devices.
9.3.1 Electrochemical Aptasensors
Electrochemical aptasensors contains a surfaced functional electrode as the platform for biological sensing aptamer immobilization. The electrochemical current
variations can monitor the analyte-binding event, which can be used for analyte
detection. Electrochemical transduction can be achieved through many approaches,
such as impedimetric, potentiometric, amperometric, and photo-electrochemical.
The electrochemical aptasensors can offer several advantages, as readily miniaturized, low cost of production without expensive optical instruments, and especially
high sensitivity, which can approach the clinical testing requirements. And also, these
aptamer-based electrochemical platforms can be label-free and reusable, promising
for real-time monitoring.
The vascular endothelial growth factor (VEGF) is a regulator for vascular permeabilization and angiogenesis, and the most abundant and potent isoform, VEGF 165 ,
has been identified as cancer biomarkers [33]. The electrochemical biosensor should
construct with the aptamer as a recognition element and a catalytic redox reaction must happen to transfer electrons to the electrode [34]. Qureshi et al designed
an on-chip aptamer-antibody sandwich-type electrochemical biosensor for VEGF
protein sensing, using the gold microelectrodes arrays. The aptamer-VEGF protein
complex was then captured by antibody-coated magnetic beads, resulting in the
change in capacitance and impedance. The capacitance change was quantified by
non-Faradaic electrochemical impedance spectroscopy (nFIS) [35]. Carbon or metal
nanomaterials are used for electrochemical aptasensor establishment, and the surface
modification could enhance the electrical signal [36]. Another research reported an
ultra-traceVEGF 165 -sensing aptasensor based on the nanocomposite platform (BSAAuNCs/IL) functional glassy carbon electrode for aptamers immobilization. The
VEGF binding could cause a decrease of differential pulse voltammetry current
together with more mass-transfer limiting to the electrode surface. The benefit of the
large surface area of gold-nanocluster for VEGF immobilization, more this sensor
could achieve the detection range of 2.5–250 pM with limit of detection (LOD)
of 0.48 pM [37]. By utilization the ordered mesoporous carbon-gold nanocomposites (OMCeAu-NCs)modified screen-printed electrode to immobilize the VEGF
aptamers, the electrochemical sensor could detect VEGF in serum range from 10.0
to 300.0 pg/mL with LOD of 1.0 pg/mL using cyclic voltammetry along with electrochemical impedance spectroscopy [38]. A sandwich electrochemical aptasensor
based on graphite screen-printed electrodes was established with thiolated DNA
aptamer and secondary biotinylated aptamer. This strategy showed the LOD of
30 nmol/L by means of differential pulse voltammetry (DPV) [39].