Electroactive indicators

Electrochemical detection of successful DNA hybridization events should be also considered. Although it is based mostly on external electrochemical markers, such as electroactive indicators or enzymes, the exploitation of the intrinsic DNA oxidation signal requires a multi-site attachment such as adsorption as the immobihzation technique. 

Template-free MIP film impermeable for electroactive indicator... 

A Electroinactive analyte fed MIP particle Electroactive competitor Electroactive indicator... 

Keywords Carbon screen printed electrodes Genosensors Electrochemical adsorption Hybridization event Electroactive indicators Indicator-free electrochemical genosensor... 

In literature two possibilities for the detection of a DNA hybridization event in the case of carbon SPE genosensor are reported to use electroactive indicators or to detect the guanine moiety signal per se (label-free). 

Sequence-Specific Hybridization Genosensors based on Electroactive Indicators... 

It has been pointed out that nonspecific adsorption can also influence the results of hybridization sensors based on electroactive indicators. 

Indicators associating preferentially with ssDNA have been advantageously used with electrochemical DNA hybridization sensors. For instance, the phenothiazine dye methylene blue (MB) associates with unpaired guanine moieties. In dsDNA this interaction is hampered, which results in decrease in the current response due to MB reduction [22]. On the other hand, there are also ds-specific electroactive indicators such as the intercalator ferrocenyl naphthalene diimide, which results in a detection limit of 10 zmol at the differential pulse voltammetric mode [23,24]. 

Figure 14.17. Schematic representation of the enhanced detection of DNA hybridization based on a DNA-MWCNT sensor using daunomycin as the electroactive indicator.

Nucleic acid biosensors using electrochemical detection schemes have been reported [53-57]. These biosensors normally involve inunobilization of single-stranded DNA (ssDNA) at an electrode surface and hybridization is measured by monitoring changes in the redox properties of an electroactive indicator that is physically associated with the nucleic acid material. 

Table 1 Electroactive indicators commonly used for the biosensing of DNA hybridization...

CdL2] as electroactive indicator, the hybridization between the probe and its complementary ssDNA, was investigated by DPV. Experiment with non-complementary oligonucleotides was carried out to assess the selectivity of the developed electrochemical DNA biosensor. The complementary HBV DNA could be quantified ranged from 1.01 xlO to 1.62 xlO mol L with good linearity (r = 0.9962). The detection limit was 7.19 xlO mol L (3[Pg.136]

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