title: Label-free electrochemical aptasensor for femtomolar detection of 17β-estradiol.
abstract: We report an electrochemical aptasensor for the rapid, label-free detection of 17β-estradiol (E2) from femtomolar to micromolar levels. The sensor features an aptamer-functionalised nanoporous conducting polymer electrode whose surface potential is probed via electrochemical impedance spectroscopy. The unprecedented detection limit for E2 is explained via the redistribution of negative charges in the electrode double-layer region when the aptamer adopts a folded conformation around the small neutral target molecule. The sensor responds approximately logarithmically over a wide dynamic range of E2 concentration that spans biological trigger levels, with excellent discrimination against structurally similar molecules including progesterone, and robust operation in human urine. The generality of the approach of using conformationally gated small molecule binding aptamers is highlighted with a further example of adenosine detection via the adenosine binding aptamer.
authors.affiliation: Polymer Electronics Research Centre, School of Chemical Sciences, University of Auckland, 23 Symonds Street, Auckland, New Zealand.
authors.forename: Bicheng
authors.initials: B
authors.lastname: Zhu
authors.affiliation: School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6012, New Zealand; The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand.
authors.forename: Omar A
authors.initials: OA
authors.lastname: Alsager
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, Wellington 6012, New Zealand.
authors.forename: Shalen
authors.initials: S
authors.lastname: Kumar
authors.affiliation: School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6012, New Zealand; The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand. Electronic address: Justin.Hodgkiss@vuw.ac.nz.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Hodgkiss
authors.affiliation: Polymer Electronics Research Centre, School of Chemical Sciences, University of Auckland, 23 Symonds Street, Auckland, New Zealand; The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand. Electronic address: j.travas-sejdic@auckland.ac.nz.
authors.forename: Jadranka
authors.initials: J
authors.lastname: Travas-Sejdic
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D003217:Conductometry / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004958:Estradiol / Q000032:analysis* / Q000652:urine*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013194:Staining and Labeling; D014867:Water / Q000737:chemistry*
chemical_list: D052157:Aptamers, Nucleotide; D014867:Water; D004958:Estradiol
keywords: 17β-estradiol; Aptasensor; Electrochemical impedance spectroscopy; Interfacial charge redistribution; Polypyrrole