Electrochemical behaviour of 2,4-dinitrophenylhydrazi(o)ne as multi-redox centre DNA label at mercury meniscus modified silver solid amalgam electrode

Abstract

A detailed voltammetric study of 2,4-dinitrophenylhydrazine (DNPH), a DNPH modified nucleotide (dCDNPHMP) and a short single stranded DNA (ssDNA-DNPH) at mercury meniscus modified silver solid amalgam electrode (m-AgSAE) is presented in this work. Electrochemical behaviour of these compounds was studied using cyclic voltammetry (CV), adsorptive stripping CV and open circuit adsorptive transfer stripping CV. Adsorptive and transfer stripping techniques offered sensitive detection of the studied compounds at submicromolar levels with low sample volume consumption (about 0.5μl), respectively. The ssDNA-DNPH gives three specific cathodic signals related to the reduction of the redox label. All these signals advantageously appear at significantly less negative potentials than unmodified nucleic acid and they may be optionally switched on/off by properly adjusted potential windows and scan rates. This opportunity increases signal response diversity and selectivity in DNA sensing. Mechanism of electrochemical reduction of the studied compounds is proposed. Thanks to a better mechanical stability, easy handling and sufficient sensitivity, the m-AgSAE appears/seems to be more potent alternative to the hanging mercury drop electrode and better suited for biosensor development. Successful incorporation of the DNPH labeled nucleoside triphosphate into the DNA structure shows that selected DNA polymerase tolerates this bulky moiety and can be used, in combination with electrochemical methods utilizing m-AgSAE, in further development of various applications.