Sensitive determination of oligodeoxynucleotides by anodic adsorptive stripping voltammetry at surface-roughened glassy carbon electrode in the presence of copper
A sensitive voltammetric detection of different oligodeoxynucleotide (ODN) samples at the surface-roughened glassy carbon electrode (GCE) is described. The optimisation of the measurement showed that the most sensitive detection of the ODN samples can be performed at the GCE mechanically polished by abrasion particles with diameter of about 15 mu m (15 mu M GCE; 1200-grid silicon carbide paper). The heights of the ODN signals at the GCE polished with I gm diamond paste (1-mu m GCE) were about 22-times less than on the 15-mu m GCE. An atomic force microscope (AFM) was used for characterisation of the surface roughness of the mechanically polished GCE by different abrasion particles. The proposed electrochemical method for the detection of different ODNs is based on the following steps: (i) before voltammetric measurement the acidic hydrolysis of the ODN (ahODN) sample was performed; (ii) the second step includes a potential-controlled reduction of Cu(11) and accumulation of the purine base residue-Cu(I) complex (ahODN-Cu(I) complex) at the GCE; (iii) finally, followed the anodic stripping of the electrochemically accumulated ahODN-Cu(I) complex from the GCE. The anodic stripping of the accumulated ahODN-Cu(I) complex produced a well-developed voltammetric signal (peak 1) at around +0.28 V. At more positive potentials a second voltammetric signal (peak 11) corresponding to the oxidation of adenine residues can be detected. The intensity of peaks I and II of the ahODN-Cu(I) complex increased linearly with the length of ahODNs containing only adenine units. We observed a good correlation between the number of purine units within the ODN-chain and the height of the peak I of the electrochemically accumulated ahODN-Cu(I) complex. (c) 2005 Elsevier B.V. All rights reserved.