title: Label-Free, Electrochemical Quantitation of Potassium Ions from Femtomolar Levels.
abstract: In this communication, a label-free and sensitive electrochemical method to detect potassium ions is proposed. The conducting polymer polypyrrole was used as both an anchor for the probe and a transducer of the detection event. A K(+)-specific G-rich aptamer was applied as a recognition element, which folded into the G-quadruplex structure in the presence of K(+), and this resulted in an increase in the electrode impedance. The combination of the K(+)-selective aptamer and the porous conducting polymer as a signal transducer afforded a successful sensor platform. The sensor responded approximately logarithmically over a wide dynamic range of K(+) concentrations from 20 fM to 1 mM, with a very low detection limit of 14.7 fM and excellent discrimination against other ions. Additionally, electrochemical impedance spectroscopy was used to study the kinetics of K(+) binding at the conducting polymer-immobilized aptamer surface, which indicated strong binding between the two. This work demonstrates a powerful approach for the sensitive, selective, and direct electrochemical detection of metal ions based on the switching conformation of G-rich aptamers attached to a porous conducting polymer surface. This assay scheme can be expanded to the detection of a wide range of targets by modifying the aptamer structure as a recognizing moiety.
authors.affiliation: School of Chemical Sciences, Polymer Electronics Research Centre (PERC), The University of Auckland, 23 Symonds Street, Auckland, New Zealand.
authors.forename: Bicheng
authors.initials: B
authors.lastname: Zhu
authors.affiliation: Digital Sensing Limited, 16 Beatrice Tinsley Cresent, Albany, Auckland, 0632, New Zealand.
authors.forename: Marsilea A
authors.initials: MA
authors.lastname: Booth
authors.affiliation: Department of Cogno Mechatronics Engineering, Pusan National University, Miryang, 627-706, Republic of Korea.
authors.forename: Han Young
authors.initials: HY
authors.lastname: Woo
authors.affiliation: The MacDiarmid Institute for Advanced Materials and Nanotechnology, Laby 410, Gate 6 Kelburn Parade, Kelburn, Wellington, New Zealand.|School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Hodgkiss
authors.affiliation: School of Chemical Sciences, Polymer Electronics Research Centre (PERC), The University of Auckland, 23 Symonds Street, Auckland, New Zealand. j.travas-sejdic@auckland.ac.nz.|The MacDiarmid Institute for Advanced Materials and Nanotechnology, Laby 410, Gate 6 Kelburn Parade, Kelburn, Wellington, New Zealand. j.travas-sejdic@auckland.ac.nz.
authors.forename: Jadranka
authors.initials: J
authors.lastname: Travas-Sejdic
mesh_terms: D055664:Electrochemical Techniques / Q000379:methods*; D004566:Electrodes; D058085:Iron Compounds; D057230:Limit of Detection; D011188:Potassium / Q000737:chemistry*
chemical_list: D058085:Iron Compounds; D011188:Potassium
keywords: aptasensors; electrochemistry; kinetics; polymers; potassium