Biomedical Engineering Reference
In-Depth Information
labels through layer-by-layer (LBL) assembly of CdTe QDs onto the surfaces of
the polystyrene (PS) microbeads. Instead of the conventional single CdTe QD one,
numerous CdTe QDs were involved in each molecular recognition event, which
were illuminated in Fig.
4.6
. The analytical signal output was thus expected to be
dramatically amplified. With this new PS-(CdTe)
2
labels, about 2-4 orders of mag-
nitude improvement in detection limit for thrombin is obtained compared with that
of other universal signal amplification routes. The detection limit could be pushed
down further by increasing the number of CdTe QD layer coated on the PS beads.
Besides the traditional QDs, Xu's group [
64
] reported the highly enhanced ECL
from a nitrogen doped TiO
2
nanotube array. They found that the nitrogen incor-
porated in TiO
2
NTs could greatly enhance the ECL intensity and make the ECL
spectrum red shift. Using K
2
S
2
O
8
as the coreactant, the TiO
2
-N NTs electrode can
enhance the ECL intensity by 10.6-fold and move the onset ECL potential more
positively by about 400 mV as compared to the pure TiO
2
NTs electrode. And the
possible mechanism was forwarded as following:
S
2
O
8
2
−
+e
→
SO
4
2
−
+ SO
4
·−
(4.34)
SO
4
·−
SO
4
2
−
+h
+
→
(4.35)
-N+h
+
→
N - TiO
2
(
h
+
)
TiO
2
(4.36)
N-TiO
2
(
h
+
)+
e
−
→ (
N-TiO
2
)
∗
(4.37)
(
N-TiO
2
)
∗
→
N-TiO
2
+
H
(4.38)
Fig. 4.6
Schematic presentation of the PS-(CdTe)
2
assembly-labeled ECL detection of throm-
bin. Reprinted with permission from Ref. [
68
]. Copyright 2011 Elsevier
