Probe electrochemical/redox-active

Electrochemical methods involve redox behavior of probes or the polymers themselves. It is possible to utilize this technique to investigate permselectivity (86). It can be utilized to probe any redox active species in the polymer films. 

The intercalation of polycyclic aromatic compounds into duplex DNA structures was used to develop nucleic acid-based electrochemical sensors.66 For example, the bis-ferrocene-tethered naphthalene diimide (16) was used as a redox-active intercalator to probe DNA hybridization.67 The thiolated probe was assembled on a Au electrode, and the formation of the duplex DNA with the complementary analyte nucleic acid was probed by the intercalation of (16) into the double-stranded nucleic acid structure and by following the voltammetric response of the ferrocene units (Fig. 12.17a). The method enabled the analysis of the target DNA with a sensitivity that corresponded to ca. 1 x 10-20mol. 

Within a regular scanning electrochemical microscopy (SECM) system, the probe microelectrode, called the tip electrode, can be precisely positioned several micrometers away from a substrate under the control of a three-dimensional motorized positioner in the solution containing redox-active species. By scanning the SECM tip within the plane paralleling a substrate surface and simultaneously monitoring tip current (/ [ ), which is sensitive to the presence of conducting and... 

Fig. 5 Immobilized nucleic acid assays utilizing redox-active moieties, a Amplified detection of viral DNA by generation of a redox-active replica and the bioelectrocatalyzed oxidation of glucose (Reprinted with permission from [200]. Copyright(2002) American Chemical Society), b Alternative formats for the capture on a gold electrode SAM of solution-extended primers or direct surface extension of primer with electrotides (adapted from [185]). c Ferrocene-labelled hairpin for electrochemical DNA hybridization detection. A Fc-hairpin-SH macromolecule is immobilized on a gold electrode. When a complementary DNA target strand binds to the hairpin, it opens and the ferrocene redox probe is separated from the electrode, producing a decrease in the observed current (Reprinted with permission from [203], Copyright(2004) American Chemical Society)...

The light-induced control of the electroactivity of charged redox-active substrates allows the functionalized electrode to be used to control electrochemical transformations. A system composed of two oppositely charged diffusional redox probes—positively charged 2,5-bis[[2-(dimethylbutylammo-nio)ethyl]amino]-l,4-benzoquinone (14) and negatively charged pyrrolo-quinoline quinone (PQQ) (15)—was used to demonstrate this behavior... 

An alternative approach for utilizing DNA thin films for electrochemical sensors involves using redox-active probe molecules intercalated into the Ji-stack. Fig 5-lb. This approach has been successfully employed in the design of electrochemical assays for hybridization,single-base mismatches, and chemical modifications and lesions within duplex DNA. It has also provided provocative experimental results regarding charge transport through the double helix. ... 

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