Fast Scan Cyclic Voltammetry As a DNA Sensor Using Carbon Fiber Microelectrodes
Authors: Liu Favian Alberto , Asrat Thomas Michael , Zestos Alexander George 
Published: May 2020

Over the past five decades and since the discovery of the structure of nucleic acids (DNA and RNA), different technological advancements have been achieved to understand the overall biochemical properties of nucleic acids. The electrochemical reactivity of these nucleobases defines the overall reactivity of DNA. So far, technological progress on the development of electrochemical DNA biosensors has been applied on different biomedical and environmental analyses which includes, analysis of infectious diseases, diagnosis and treatment of cancer and extensive studies on neurodegenerative and genetic diseases. As nucleic acids are the profound and vital biomolecules of all living things, they are still the center of intensive research. The building blocks of DNA are purine bases, adenine and guanine and pyrimidine bases, thymine and cytosine, where each base is attached to the pentose sugar with phosphate group.

Fast scan cyclic voltammetry (FSCV) is an electroanalytical technique which applies a voltage in a fast (greater than 400 V/s) and repeating manner to a working electrode and records the resultant current produced by oxidation of analyte at the electrode surface. Previous research by Venton and colleagues has shown that the electroactive nucleosides and nucleotides can be oxidized at a voltage of a specific waveform, using carbon fiber-microelectrode (CFME). The applied voltage can only oxidize specific nucleobases such as purines and the peak oxidative current is analyzed to quantify the concentration of the analyte.

When co-detecting the purine nucleosides, the two primary oxidative peaks interfere with each other. As a result, a scalene waveform for the co-detection of adenosine and guanosine, initially developed by Ross et. al, was adapted to help with the co-detection of purine bases adenine and guanine in DNA. The used waveform sweeps up at 150 V/s from -0.4 to 1.45 V and sweeps back at 400V/s vs. a silver-silver chloride (Ag/AgCl) reference electrode. Adenine was recorded to have two oxidative peaks at 1.34 V on the backward scan (primary peak) and another at 1 V on the forward scan (secondary scan). The two peaks come from the oxidation of C2 and C8 into ketones. In addition, guanine was recorded to have two oxidative peaks at 1.2 V on the forward scan (primary peak) and another at 0.7 V on the backward scan (secondary peak). The two peaks are from the oxidation of C8 into a ketone and the oxidation of N7 after it has lost its hydrogen from the oxidation of C8. The structure of the DNA sample, (ssDNA, dsDNA, synthetic DNA, bacterial DNA, short base pairs and longer base pairs), determines the shape and measurement of the peak oxidative current of adenine and guanine, which is a molecular fingerprint for analyte detection. Due to the nature of DNA, we are able to amplify and manipulate it using biochemical methods. However, nucleic acid base pairing has to be taken into account and a strategy to detect target sequences with an electrode must be implemented. Based on the analyzed data from this experiment, this analytical method and measurement can be useful in detecting different physical and structural DNA damage and opens a way for studies on a potentially new diagnostic and treatment mechanisms. This work could potentially develop an entire new class of biosensors for DNA, RNA, and other nucleic acids, which would have lasting impacts in the field of sensor diagnostics.