title: A label-free electrochemical DNA sensor based on exonuclease III-aided target recycling strategy for sequence-specific detection of femtomolar DNA.
abstract: The present work demonstrates a rapid, single-step and ultrasensitive label-free and signal-off electrochemical sensor for specific DNA detection with excellent discrimination ability for single-nucleotide polymorphisms, taking advantage of Exonuclease III (Exo III)-aided target recycling strategy to achieve signal amplification. Exo III has a specifical exo-deoxyribonuclease activity for duplex DNAs in the direction from 3' to 5' terminus, however its activity on the duplex DNAs with 3'-overhang and single-strand DNA is limited. In response to the specific features of Exo III, the proposed E-DNA sensor is designed such that, in the presence of target DNA, the electrode self-assembled signaling probe hybridizes with the target DNA to form a duplex in the form of a 3'-blunt end at signaling probe and a 3'-overhang end at target DNA. In this way, Exo III specifically recognizes this structure and selectively digests the signaling probe. As a result, the target DNA dissociates from the duplex and recycles to hybridize with a new signaling probe, leading to the digestion of a large amount of signaling probes gradually. A redox mediator, Ru(NH(3))(6)(3+) (RuHex) is employed to electrostatically adsorbed onto signaling probes, which is directly related to the amount and the length of the signaling probes remaining in the electrode, and provides a quantitative measure of sequence-specific DNA with the experimentally measured (not extrapolated) detection limit as low as 20 fM. Moreover, this E-DNA sensor has an excellent differentiation ability for single mismatches with fairly good stability.
authors.affiliation: Lab of Biosystems and Microanalysis, State Key Laboratory of Bioreactor Engineering, East China University of Science & Technology, Shanghai, 200237, China.
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.forename: Bin-Cheng
authors.initials: BC
authors.lastname: Yin
authors.forename: Bang-Ce
authors.initials: BC
authors.lastname: Ye
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D004247:DNA / Q000032:analysis*; D055664:Electrochemical Techniques / Q000379:methods*; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D012680:Sensitivity and Specificity
chemical_list: D004247:DNA; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III