DEVELOPMENT AND APPLICATIONS OF NANOMATERIALS ENRICHED APTAMER BASED ELECTROCHEMICAL BIOSENSORS

Project no. 21648 · Status: Kapanmış · 2020

Summary

Within the scope of this project based on PhD thesis, it is aimed to synthesize functional electrode surfaces to serve as a platform for aptasensor development. Single-use pencil graphite electrode PGE surfaces were deposited with nanostructured manganese and molybdenum oxides by either cyclic voltammetry (CV) or pulsed deposition (PD) techniques. These transition metal oxides were chosen due to their availability and low-cost, and other unique advantages such as biocompatibility and catalytic performances. Then, the aptamers specific to the target molecules were immobilized by either carbodiimide chemistry or adsorption onto the electrode surface. Performances of the aptasensors developed by this means have been compared in clinical and food analysis.In the first part of the study, aptasensors for a mycotoxin, Ochratoxin A (OTA) widely encountered in foodstuff was developed and electrochemical impedance spectrometric (EIS) measurements were used to evaluate the performances of the electrodes. Amino-terminated aptamers were immobilized by EDC/NHS mechanism onto the CV or PD deposited MnOx/PGE or MoOx/PGE and the difference in their charge transfer resistances (DRct) were compared to those obtained with the thiol-terminated aptamer by adsorption through Au NP decorated onto the metal oxide film deposited electrode surfaces. After characterization of the best responded electrode surfaces (MnOx (PD)/PGE), analytical characteristics of the method was studied and the limit of detection (LOD) (S/N=3) was calculated as 0.025 nM well below of the lowest limit for OTA in grape juice set by European Community being 2 nM. Selectivity of the method was proven by comparing the DRct values obtained for the most possible interferents namely, Aflatoxin B1 and Zearalenone. Then, the method was applied to grape juice samples and satisfactory recovery values have been obtained.In the second part, another aptasensor development based on transition metal oxides for diagnosis of early-stage cancer was targeted and prostate cancer cell was chosen as the model. Recently, the development of aptamers has accelerated the studies on the determination of PSA in serum but, direct cellular analyses is required for a reliable diagnosis. Therefore, in this part of the study, after the modification of the PGE surfaces with transition metal oxides, carbodiimide chemistry was utilized in attachment of the aptamer specific to the PSA. Then, the prostate cancer cells cultivated by cell culture was investigated by EIS. A label-free, fast, specific, and inexpensive analysis methods have been developed by this means.

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