Biology Reference
In-Depth Information
Table 2.2. Aptamer-based biosensors based on the “switch-on” or
“switch-off”approach
Target
Signal Label
AnalyticalCharacteristics References
Cocaine
ON
MB
Baker
et al.
(2006)
Thrombin
ON
Ferrocene
DL 0.5 nM
Radi
et al.
(2006)
Thrombin
OFF
MB
DL 3 nM
Xiao
et al.
(2005)
DL 0.02
μ
M
Adenosine
OFF
Ferrocene
Wu
et al.
(2007)
[Ru(NH
3
)
6
]
3
+
0.5
μ
g/mL
Lysozyme
OFF
Cheng
et al.
(2007)
DL 2
μ
M
Theophylline ON
MB
Feropontova
et al.
(2009b)
Thrombin
ON
Ferrocene
Picomolar range
Huang
et al.
(2008)
Thrombin
ON
Ferrocene
DL 30 fM
Mir
et al.
(2008)
Cocaine
ON
MB
Low micromolar
Swensen
et al.
(2009)
Thrombin
ON
Glucose/Glucose DL 2.5 nM
Tan
et al.
(2009)
oxidase
Thrombin
OFF
Ferrocene
DL 3.9 nM
Tan
et al.
(2009)
Adenosine
OFF
MB
DL 0.01
μ
M
Wang
et al.
(2009)
Botulinum
OFF
Fluorescein/anti- DL 40 pg/mL
Wei
et al.
(2009)
neurotoxin
fluorescein-HRP
PDGF
ON
MB
DL 50 pM
Rodriguez
et al.
(2005)
becomes an intrinsic part of the nucleic acid structure [35]. This
feature represents an almost unique mechanism that can be
exploited in the design of new electrochemical biosensors [2]. In
this approach the interaction of a labeled aptamer with its tar-
get can modulate the distance of the electroactive labels from the
sensor electrode, thereby altering the redox current. Various
aptasensors (Table 2.2), based on this approach, are used for the
detectionofdifferenttargetssuchastheophylline[36,37],lysozyme
[38], botulinum neuorotoxin [39], adenosine [40, 41], cocaine [42],
or thrombin [43-45].
In the two studies using a “signal-off” approach by Xiao
et al.
[44, 45], thrombin was detected by monitoring the decrease in the
amperometric response of a redox label present at one end of the
thrombin aptamer as a result of the association of thrombin with
the aptamer. The interaction of the labeled aptamer with its target
modulates the distance of the electroactive labels from the sensor
electrode, thereby altering the redox current. In the absence of the
