Aptamer substrate complexes, formation

The formation of aptamer-substrate complexes was also followed by the use of redox-active intercalators73 (Fig. 12.18d). A nucleic acid hairpin structure that contained in its single-stranded loop the antithrombin base sequence was assembled on a Au electrode, and methylene blue was intercalated as a redox label in the double-stranded stem of the hairpin structure. The hairpin was, then, opened in the presence of thrombin, by generating the respective G-quadruplex-thrombin complex, and as a result, the redox label was removed from the nucleic structure, showing a decrease in the voltammetric response with the increase in the concentration of thrombin. This method enabled the analysis of thrombin with a detection limit that corresponded to... 

We further addressed the use of the nucleic acids as biopolymers for the formation of supramolecular structures that enable the electronic or electrochemical detection of DNA. Specifically, we discussed the use of aptamer/low-molecular-weight molecules or aptamer/protein supramolecular complexes for the electrical analysis of the guest substrates in these complexes. Also, nucleic acid-NPs hybrid systems hold a great promise as sensing matrices for the electrical detection of DNA in composite three-dimensional assemblies. While sensitive and selective electrochemical sensors for DNA were fabricated, the integration of these sensor configurations in array formats (DNA chips) for the multiplexed analysis of many DNAs can also be envisaged. 

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