Development of QTF-based electrochemical aptasensor for sarcosine detection

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Uludağ İ., Özyurt C., Ünal M. A., Sezgintürk M. K., Özkan S. A.

5th International Congress on Biosensors, Çanakkale, Turkey, 21 - 23 September 2022, pp.1

  • Publication Type: Conference Paper / Full Text
  • City: Çanakkale
  • Country: Turkey
  • Page Numbers: pp.1
  • Çanakkale Onsekiz Mart University Affiliated: Yes



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









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




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.





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.




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.


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.



1. Randviir, E. P., & Banks, C. E. (2013). Electrochemical impedance spectroscopy: an overview of bioanalytical applications. Analytical methods, 5(5), 1098-1115.

2. Sharma, T. K., Bruno, J. G., & Dhiman, A. (2017). ABCs of DNA aptamer and related assay development. Biotechnology advances, 35(2), 275-301.

3. Jin, C., Qiu, L., Li, J., Fu, T., Zhang, X., & Tan, W. (2016). Cancer biomarker discovery using DNA aptamers. Analyst, 141(2), 461-466.

4. Musumeci, D., Platella, C., Riccardi, C., Moccia, F., & Montesarchio, D. (2017). Fluorescence sensing using DNA aptamers in cancer research and clinical diagnostics. Cancers, 9(12), 174.

5. Yan, R., Lu, N., Han, S., Lu, Z., Xiao, Y., Zhao, Z., & Zhang, M. (2022). Simultaneous detection of dual biomarkers using hierarchical MoS2 nanostructuring and nano-signal amplification-based electrochemical aptasensor toward accurate diagnosis of prostate cancer. Biosensors and Bioelectronics197, 113797.

6. Özyurt, C., Canbay, Z. Ç., Dinçkaya, E., & Evran, S. (2019). A highly sensitive DNA aptamer-based fluorescence assay for sarcosine detection down to picomolar levels. International journal of biological macromolecules129, 91-97.