Label-free electrochemical aptasensor for femtomolar detection of 17β-estradiol

• Published in: Biosensors & bioelectronics 2015-08, Vol.70, p.398-403
• Main Authors: Zhu, Bicheng, Alsager, Omar A., Kumar, Shalen, Hodgkiss, Justin M., Travas-Sejdic, Jadranka
• Format: Article
• Language: English
• Subjects: 17β-estradiol; Adenosines; Aptamers, Nucleotide - chemistry; Aptasensor; Binding; Biotechnology; Conducting polymers; Conductometry - instrumentation; Electrochemical impedance spectroscopy; Electrodes; Equipment Design; Equipment Failure Analysis; Estradiol - analysis; Estradiol - urine; Human; Interfacial charge redistribution; Polypyrrole; Reproducibility of Results; Sensitivity and Specificity; Sensors; Staining and Labeling; Urine; Water - chemistry
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2015.03.050

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. [Display omitted] •An effective, direct electrical and label-free detection of 17β-estradiol using aptamer-bound nanoporous conducting polymer modified electrodes was developed.•High sensitivity, a wide dynamic range, superb selectivity and good performance in biological and environmental samples were achieved.•Interfacial charge redistribution model was employed to model the nanoporous conducting polymer based on aptasensor characteristics.•We demonstrated the developed methodology is a general approach to detect small molecules based on the conformational change of aptamers.