title: Re-engineering aptamers to support reagentless, self-reporting electrochemical sensors.
abstract: Electrochemical aptamer-based (E-AB) sensors have emerged as a promising and versatile new biosensor platform. Combining the generality and specificity of aptamer-ligand interactions with the selectivity and convenience of electrochemical readouts, this approach affords the detection of a wide variety of targets directly in complex, contaminant-ridden samples, such as whole blood, foodstuffs and crude soil extracts, without the need for exogenous reagents or washing steps. Signaling in this class of sensors is predicated on target-induced changes in the conformation of an electrode-bound probe aptamer that, in turn, changes the efficiency with which a covalently attached redox tag exchanges electrons with the interrogating electrode. Aptamer selection strategies, however, typically do not select for the conformation-switching architectures, and as such several approaches have been reported to date by which aptamers can be re-engineered such that they undergo the binding-induced switching required to support efficient E-AB signaling. Here, we systematically compare the merits of these re-engineering approaches using representative aptamers specific to the small molecule adenosine triphosphate and the protein human immunoglobulin E. We find that, while many aptamer architectures support E-AB signaling, the observed signal gain (relative change in signal upon target binding) varies by more than two orders of magnitude across the various constructs we have investigated (e.g., ranging from -10% to 200% for our ATP sensors). Optimization of the switching architecture is thus an important element in achieving maximum E-AB signal gain and we find that this optimal geometry is specific to the aptamer sequence upon which the sensor is built.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: White
authors.forename: Aaron A
authors.initials: AA
authors.lastname: Rowe
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Plaxco
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D052157:Aptamers, Nucleotide / Q000737:chemistry*; D001483:Base Sequence; D015374:Biosensing Techniques; D055664:Electrochemical Techniques / Q000379:methods*; D004566:Electrodes; D006801:Humans; D007073:Immunoglobulin E / Q000737:chemistry; D016376:Oligonucleotides, Antisense / Q000737:chemistry; D010084:Oxidation-Reduction
chemical_list: D052157:Aptamers, Nucleotide; D016376:Oligonucleotides, Antisense; D007073:Immunoglobulin E; D000255:Adenosine Triphosphate