Development of electrochemical nucleic acidbiosensors for biomolecular interactions

In the first part of this study, in order to develop electrochemical biosensors in which the determination of microRNA can be performed more quickly, practically and with low cost by means of biomolecular interaction based on nucleic acid hybridization. A novel biosensor was devloped for the determination of microRNA-34a as a major biomarker in the diagnosis of cancer and many diseases by modifying the surface of disposable pencil graphite electrode (PGE) via covalent agent (CA) and ionic liquid (IL). Microscopic characterization of sensor surface was done by scanning electron microscopy (SEM) and electrochemical characterization by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. DNA probe concentration, probe immobilization time on to electrode surface, miRNA-34a target concentration, hybridization time and immobilization time for hybrid onto the electrode surface were optimized by using EIS technique. Detection of miRNA-34a based on biomolecular interaction after hybrid formation between the DNA probe and miRNA-34a target was performed by monitoring the charge transfer resistance (Rct) by EIS technique. In order to investigate the applicability of the developed biosensor, miRNA detection was also performed in artificial serum medium (FBS). The selectivity of impedimetric biosensor to miRNA-34a was also tested in the presence of other non-complementary miRNA sequences both in buffer media, or diluted FBS. In the second part of this study, PGE was used to investigate the biointeraction of mycotoxin, Fumonisin B1 (FB1) with double helix DNA for the first time in the literature by using EIS technique. DNA concentration, FB1 concentration and interaction time etc. were optimized. The interaction of FB1 with dsDNA was also tested in the mixture (1:1) of other mycotoxins, such as Zearalenone (ZEN), Deoxyvinalenol (DON), Ochratoxin A (OTA) for testing the selectivity of impedimetric biosensor to FB1. Biomolecular interactions based on single-use electrochemical biosensors in this study conducted with a more sensitive, rapid and selectively reproducible results can be obtained by analyzing the determination of different types of miRNAs and toxins in the future.