Recent years have seen the development of a new class of reagentless, electrochemical sensors utilizing electrode-bound, redox-tagged oligonucleotide probes as their sensing elements. To date, these E-DNA (electrochemical DNA) and E-AB (electrochemical, aptamer-based) sensors have been reported against specific DNA and RNA sequences, proteins, small molecules and inorganic ions. Because all of the sensing components in E-DNA and E-AB sensors are covalently attached to the interrogating electrode, they do not require labeling of the target molecules or the use of exogenous reagents. Likewise, because E-DNA and E-AB signal generation is linked to specific, binding induced changes in the dynamics of the probe DNA (rather than changes in absorbed mass, charge etc.), these sensors show no loss in functionality when challenged with complex, contaminant-ridden samples such as blood serum, soil extracts and foodstuffs.

Despite their many potentially promising attributes, the E-DNA/E-AB class of sensors suffers from a potentially important drawback: to date these sensors have been limited to the detection of targets that bind to unmodified DNA or RNA sequences. And while the use of aptamers as recognition elements has greatly expanded the range of targets that can be addressed using DNA- or RNA-based recognition elements, the further expansion of the E-DNA platform to the detection of targets that, for example, bind specific small molecules might be of utility. The observation that E-DNA/E-AB signaling requires only that target binding alters the dynamics of the DNA-bound redox tag suggests a straightforward means by which the platform's range can be expanded by appending new recognition elements to the DNA probe normally employed. To test this hypothesis we demonstrate here an E-DNA-like platform that combines the reagentless, electrochemical detection of the E-DNA platform with the recognition properties of specific small receptors.

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