ULTRASENSITIVE VOLTAMMETRIC DETECTION OF UNDERIVATIZED OLIGONUCLEOTIDES AND DNA

Electrochemical detection of nucleotides, ssDNA, and dsDNA was accompl ished by using sinusoidal voltammetric detection at copper microelectr odes, Generally, detection of these molecules utilizes the electroacti ve nature of adenine and guanine residues at most electrode surfaces. The detection approach used in this study is based on the electrocatal ytic oxidation of sugars and amines at copper surfaces, All nucleotide s and DNA molecules comprise a ribose sugar backbone and primary amine s present on the different nucleobases. Consequently, the detection ap proach is universal to all types of nucleotides, As the number of suga r moieties increases with the length of an oligonucleotide, the detect ion sensitivity is enhanced for bigger oligonucleotides, Irreversible adsorption of these oligonucleotides and other biomacromolecules like dsDNA on the electrode surface was avoided with sinusoidal voltammetry since it is a scanning electrochemical technique, The sensitivity of the detection strategy is, however, still preserved due to the effecti ve decoupling of the faradaic signal from the capacitive background cu rrents in the frequency domain. The ssDNA and dsDNA were detected in t he picomolar concentration range. The electrochemical signal due to ds DNA is actually higher than that due to ssDNA due to the larger number of easily accessible sugars on the outer perimeter of a dsDNA double helix compared to those on a ssDNA of the same size, This is in contra st to the existing electrochemical detections techniques based on the electroactivity of the nucleobase.