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@PHDTHESIS{Zhou:1009798,
author = {Zhou, Lei},
othercontributors = {Herrmann, Andreas and Offenhäusser, Andreas},
title = {{D}evelopment of novel electrochemical aptamer biosensors
for point-of-care glycemic control},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-03678},
pages = {1 Online-Ressource : Illustrationen},
year = {2024},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2025; Dissertation, RWTH Aachen University, 2024},
abstract = {Diabetes mellitus is a disease mainly induced by insulin
deficiency and/or insulin resistance, which can cause
several complications and seriously reduce the life quality
of patients. The early-stage diagnosis of this disease is
beneficial not only to diabetes monitoring but also to
treatment evaluation. The acute and long-term glycemic
control for diabetes patients commonly rely on the
assessment of the levels of blood glucose and glycated
hemoglobin A1C (HbA1C), respectively. Glycated human serum
albumin (GHSA) can be considered an alternative to HbA1C,
its lifespan is four times shorter and its concentration in
blood is independent of hemic diseases. Besides, the insulin
level of patients is also an important factor for diabetes
monitoring through glucose metabolism control, thus it is
crucial to determine the insulin concentration. Although it
is important to assess the blood glucose level, there is
also a huge necessity for insulin and GHSA determination. In
this thesis, we aim to establish aptamer-based
electrochemical sensing platforms to detect insulin and GHSA
biomarkers in high selectivity and sensitivity. Firstly, a
ratiometric electrochemical aptasensor was proposed by using
gold rod electrodes for insulin detection, then the gold rod
electrodes were used again for the determination of human
serum albumin (HSA) and GHSA, respectively. Finally, the HSA
and GHSA detection were transferred from the gold rod
electrode to a flexible polymer-MEAs chip to facilitate the
dual-detection of the two biomarkers. Firstly, a ratiometric
electrochemical aptasensor is proposed to recognize the
insulin biomarker by square wave voltammetry (SWV)
measurement with a gold rod electrode, which was immobilized
with insulin-capturing aptamer in hybridization with
partially complementary ssDNA. The capturing aptamer and
hybridized ssDNA were modified with redox tags of
anthraquinone (AQ) and methylene blue (MB) at the side
either far or close to the gold surface, respectively.
Moreover, the capturing aptamer was self-assembled on the
gold surface through functional groups of double
dithiol-phosphoramidite ((DTPA)2) thus a considerably
superior aptasensor durability can be obtained.
Monofunctional methoxy-polyethylene glycol thiol (PEG) was
used as a blocking material to passivate the gold surface
undecorated by aptamer molecules. The detection of insulin
biomarkers can cause the ssDNA dehybridization from the
capturing aptamer which leads to the formation of a typical
G-quadruplex structure during the specific binding of
insulin. Therefore, the target detection results in an
increased AQ current and decreased MB current, both of which
can be utilized to evaluate the insulin concentration. The
fabrication process as well as the target binding of this
aptasensor were characterized by different physical or
chemical techniques such as quartz crystal microbalance with
dissipation (QCM-D), atomic force microscopy (AFM),
electrochemical impedance spectroscopy (EIS), and cyclic
voltammetry (CV). The optimal aptamer concentration and
target incubation time were sequentially obtained by SWV
measurements and used in all further tests. Then, the
reliability of this aptasensor could be further improved by
operating an AND logic gate, in which the obtained current
signal only makes sense when both AQ and MB-induced signals
are different from zero. Consequently, this insulin
dual-signal aptasensor possesses a comprehensive detection
limit as low as 0.15 nM and a detection range of 0.5 nM -
2.5 µM, which is promising for the PoC diagnosis.Then, the
gold rod electrode was further employed to establish another
electrochemical aptasensor for either HSA or GHSA detection.
HSA aptamer and GHSA aptamer were accordingly applied. The
commonly used blocking material of 6-mercapto-1-hexanol
(MCH) was utilized as backfills. The aptasensor production
and target binding processes were also characterized with
AFM and EIS techniques, followed by the optimization of the
experimental conditions including the aptamer concentration
as well as the incubation time of targets. Afterwards, the
detection of HSA and GHSA were all transferred from gold rod
electrodes to the flexible multielectrode arrays
(flex⎯MEAs) facilitating the immobilization of respective
aptamer receptors. MCH was replaced with PEG backfills which
is beneficial to reduce the unspecific adsorption in real
blood sample detection. Therefore, the polymer chip is
promising for the detection of the two biomarkers only in
one mixed sample combined with the cost analysis. In this
work, the flex⎯MEAs polymer chip contains two individual
sets of gold electrodes, which are independently decorated
with respective aptamer receptors. Therefore, this
electrochemical aptasensor is capable of simultaneously
detecting the HSA and GHSA biomarkers. In this work, the
established dual-target aptasensing platform has detection
limits of 13 nM and 25 nM for HSA and GHSA, respectively,
followed by a comprehensive dynamic detection range of 40 nM
- 10 µM, covering the clinically required concentrations.In
summary, both the insulin and HSA (GHSA) aptasensors exhibit
high selectivity, durability, sensitivity as well as real
blood sample detection performance. Benefited from several
techniques such as electrochemical impedance spectroscopy,
cyclic voltammogram, atomic force microscopy,
chronocoulometry, square wave voltammetry, differential
pulse voltammetry, and quartz crystal microbalance with
dissipation monitoring, the insulin aptasensor for selective
quantification of its analyte in diluted real blood samples,
in combination with the simultaneous and quantitative
detection of HSA and GHSA ratios in concentration, allows a
reliable and cheap long-term glycemia control in PoC. Thus,
more biomarkers can be included so that a more complete and
comprehensive inspection of the glycemic surveillance
becomes realistic.},
cin = {155910 / 150000 / 057700},
ddc = {540},
cid = {$I:(DE-82)155910_20190516$ / $I:(DE-82)150000_20140620$ /
$I:(DE-82)057700_20231115$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2025-03678},
url = {https://publications.rwth-aachen.de/record/1009798},
}
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