Biopolymer-modified electrodes in the voltammetric determination of nucleic acids and proteins at the submicrogram level

Abstract

Nucleic acid- and protein-modified mercury and carbon electrodes can be prepared by immersing the electrode in a 5- μl drop of nucleic acid or protein solution. The biomacromolecule is strongly and irreversibly adsorbed at the electrode, resisting subsequent washing. The electrode is then transferred into a background electrolyte (not containing any biomacromolecule) followed by voltage scanning. This procedure is called adsorptive transfer stripping voltammetry (AdTSV). Nanogram amounts of nucleic acid can be determined with graphite electrodes, including the highly oriented pyrolytic graphite frequently used as a support in scanning probe microscopes, at relatively short waiting times without stirring of the solution. Even smaller amounts of nucleic acids are sufficient for analysis with the mercury electrode. Adsorption of DNA from different denaturing media produces DNA cyclic voltammetric peaks of different heights, suggesting that the arrangement of the DNA molecules at the electrode is influenced by the adsorption event and persists even after the electrode transfer to a non-denaturing medium. AdTSV with the mercury and graphite electrodes can be used for studies of virus suspensions producing DNA and protein signals, providing information about the virus particle degradation.