Oligonucleotides redox-modified

Numerous electrochemical strategies have been developed for the detection of mismatches in DNA. These vary from the use of electroactive DNA intercalators to enzymatic signal amplihcation schemes, or redox-modified oligonucleotides. In the following sections, we will focus on the discussion of a range of electrochemical mismatch detection schemes. 

Fig. 6. (A) The electrochemical detection of hybridization on Au electrode surface. Probe oligonucleotides with 5 -thiol are incubated on the Au surface for 12h. Strong covalent bond between thiols and Au surface results in the formation of the probe-modified electrode (A1), noncomplementary oligonucleotides are incubated with the probe-modified electrode (A2) however, no hybridization takes place between these two strands (A3), the redox label, Hoechst 33258, is incubated with the probe-modified-electrode (A4), since the redox label cannot intercalate with the single-strand probe oligonucleotides on the surface, a small electrochemical current response is obtained (A5). The current intensity at the peak potential (-0.6V) is recorded relative to the background response of the blank buffer solution (dashed grey line). (B) The electrochemical detection of hybridization on Au electrode surface. Probe oligonucleotides with 5 -thiol are incubated on the Au surface for -12 h for the preparation of the probe-modified electrode (B1), target oligonucleotides are...

Oligonucleotides modified with a terminal thiol group can be chemisorbed onto gold electrodes and, after hybridization with a soluble complementary sequence, detected voltammetrically using the redox-active bis (benzimide) dye Hoechst 33 258 [209]. This group also showed that voltammetric peak potentials for acridine orange [210] and daunomycin [211]... 

When a metal complex is formed with the nucleic acid base of single-stranded DNA (ssDNA), such ssDNA can be used as an alternative electrochemically-active DNA-binding ligand. For example, Palecek and coworkers reported the formation of a reversible redox-active metal complex by the reaction of osmium tetraoxide-pyridine with the thymine (T) base of ssDNA, and they developed an electrochemical gene detection method based on this modified oligonucleotide as a DNA probe [3]. 

---