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An Enzyme-Based E-DNA Sensor for Sequence-Specific Detection of Femtomolar DNA Targets

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journal contribution
posted on 28.05.2008, 00:00 by Gang Liu, Ying Wan, Vincent Gau, Jiong Zhang, Lihua Wang, Shiping Song, Chunhai Fan
In this work, we report an enzyme-based E-DNA sensor for the sequence-specific detection of nucleic acids. This DNA sensor employs a “stem−loop” DNA probe dually labeled with biotin and digoxigenin (DIG). The probe is immobilized at an avidin-modified electrode surface via the biotin−avidin bridge, and the DIG serves as an affinity tag for the enzyme binding. In the initial state of the sensor, the probe adopts the stem−loop structure, which shields DIG from being approached by a bulky horseradish peroxidase-linked-anti-DIG antibody (anti-DIG-HRP) due to the steric effect. After hybridization, the probe undergoes a significant conformational change, forcing DIG away from the electrode. As a result, the DIG label becomes accessible by the anti-DIG-HRP, and the target hybridization event can be sensitively transduced via the enzymatically amplified electrochemical current signal. By using this new strategy, we demonstrate that the prototype E-DNA sensor has been able to detect as low as femtomolar DNA targets with excellent differentiation ability for even single mismatches.