Electrochemical Measurements of Oligonucleotides in the Presence of Chromosomal DNA Using Membrane-Covered Carbon Electrodes

Substantial improvements in the selectivity of electrochemical measurements of trace nucleic acids are obtained by using membrane-covered carbon disk electrodes. Access to the electrode surface can be manipulated via a judicious choice of the membrane molecular weight cutoff (MWCO). The resulting separation step, performed in situ at the electrode surface, adds a new dimension of selectivity based on molecular size to electroanalysis of nucleic acids. Transport properties are evaluated with respect to the oligonucleotide length and membrane MWCO. A highly selective response is observed for synthetic oligonucleotides in the presence of otherwise interfering chromosomal DNAs. Discrimination among oligonucleotides of different lengths is also possible. Short accumulation periods (1−5 min) are sufficient for convenient measurements of low milligram per liter concentrations.