Akademik Veri Yönetim Sistemi
5th International Congress on Biosensors, Çanakkale, Türkiye, 21 - 23 Eylül 2022, ss.1
Development of QTF-based electrochemical aptasensor for sarcosine
detection
İnci Uludağ1*, Canan Özyurt2,
Mehmet Altay Ünal3, Mustafa Kemal Sezgintürk1, Sibel
Ayşıl Özkan4
1Bioengineering
Department, Engineering Faculty, Çanakkale Onsekiz Mart University, Çanakkale,
Turkey
2Department
of Chemistry and Chemical Processing Technologies, Lapseki Vocational School,
Çanakkale Onsekiz Mart University, Çanakkale, Turkey, Çanakkale, Türkiye
3 Stem Cell Institute, Ankara University, Ankara, Türkiye
4Analytical Chemistry,
Faculty of Pharmacy, Ankara University, Ankara, Türkiye
e-mail: inciuludag@comu.edu.tr
ABSTRACT
Biomarkers play an important
role in cancer diagnosis and screening, and their use could be extended to
determine and monitor prognosis. Additional testing is necessary to increase
the probability of detecting prostate cancer (PC) and reduce the number of unnecessary
biopsies. Sarcosine, an N-methyl derivative of the amino acid glycine that is
produced by glycine-N-methyltransferase, has a significant function in the
aggressiveness and development of PC. In this context, a gold quartz tuning
fork (GQTF) based aptasensor was developed to evaluate the relationship between
sarcosine levels and PC. In this study, the GQTF was used as a detection
platform for the first time to diagnose sarcosine. SH-modified sarcosine-specific
single-stranded DNA aptamers have been effectively covalently bonded on the
surface of GQTFs to provide sensitivity detection in a complicated environment
simulating urine circumstances. Electrochemical impedance spectroscopy (EIS) was
used to monitor immobilization steps and results. The optimisation research continues
for an effective immobilisation strategy.
Key
words: aptasensor, quartz tuning fork, sarcosine, prostate
cancer, electrochemical impedance spectroscopy
1. INTRODUCTION
The Randles-Ershler electrical
circuit model is the most often utilized electrical equivalent circuit model
for electrochemical reactions. This equivalent circuit model consists of the
ohmic resistance (Rs) of the electrolyte solution between the working electrode
and the reference electrode, the charge transfer resistance (Rct), and the
double-layer capacitance linked by the capacitance of the complicated bioactive
layer and Warburg. The Warburg impedance indicates the diffusion of the redox
probe from the electrode surface. EIS may also be utilized to determine
physical properties such as an electrode's surface roughness and porosity1.
Aptamers are superior than
antibodies in terms of chemical stability, affordability, and simplicity of
selection. In addition, aptamers are easily modifiable and compatible with
complicated media and matrices. In contrast to antibodies, the in vitro selection technique is
adaptable to the necessary pH, temperature, and ionic strength conditions.
Aptamers have been utilized as biorecognition components in several sensing
systems, including colorimetric, fluorometric, and electrochemical tests2.
Cancer research is one application field for aptamers, where cancer-specific
aptamers are identified and employed for diagnosis, imaging, and treatment3,4,5.
2. MATERIALS AND METHODS
Electrochemical investigations
were performed using a Gamry Reference 600 Potentiometer/Galvanometer and a 5mM
[Fe(CN)6]3-/4- 50 mM PB solution (pH 7) containing 0.01M
KCL as the redox probe. GQTF was used as the working electrode, 3M Ag/AgCl as
the reference electrode, and platinum as the counter electrode in the triple
electrode system. The GQTF electrodes were purchased from Shoulder
Crystal Company (China) and all other compounds used in this study were
obtained from Sigma-Aldrich Company (Germany). Aptamers were chosen by
employing a procedure known as systemic evolution of ligands by exponential
enrichment (SELEX), with the assistance of graphene oxide (GO), as was
mentioned in earlier research6. The flowchart of the immobilization
procedure is depicted in Figure 1.
Figure 1. A
measurement strategy and an immobilization technique for the sarcosine
aptasensor are presented.
3. RESULTS AND DISCUSSION
In this work, the electrochemical impedance
spectroscopy (EIS) method, which is a very sensitive technique, was combined
with aptamers as an identification element to detect sarcosine. It is necessary
to find the most favourable settings to construct an effective aptasensor.
Determining specific circumstances enables for setting parameters where
suitably aligned recognition components are sufficient to form a homogenous
layer. In this setting, EIS measurements at each stage supported the layer
evolution processes on the electrode surface. As observed in Figure 2, the
insulating of the surface and hence the electron transfer resistance increased,
as evidenced in the EIS Nyquist plots for each immobilization phase.
Figure 2. The proposed
aptasensor's EIS spectrum after each immobilization stage.
3.1. Optimization
studies
Optimization of experimental parameters is crucial for successful electrode
design and aptasensor progression. In this context, optimizing the
concentration of sarcosine aptamer is essential to obtaining reproducible,
sensitive and linear biosensor responses. For this purpose, GQTF electrodes
were modified with 5 and 25 nM sarcosine aptamer. Figure 3 displays the linear
calibration curves from the sarcosine aptamer concentration optimization
analysis.
Figure 3. Comparison of the
calibration graphs of the aptasensor produced with various concentrations of
sarcosine aptamer.
4. CONCLUSIONS
We aimed to develop a
disposable, affordable, simple-to-prepare, and sensitive aptasensor for
sarcosine detection. The results demonstrated that the technique has the
potential to detect sarcosine.
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