Electrochemical aptamer biosensor for DNA detection based on label-free aptamers.

• We present an electrochemical sensor for detecting DNA based on triblock DNA. • PolyA fragment has high affinity to the surface of Au electrode. • A wide linear range (10 pM-10 μM) was obtained with a detection limit of 2.9 pM. • The electrochemical sensor can detect DNA in human serum samples. Electrochemical aptasensor has been broadly advanced for nucleic acid detection. However, it is a long-term goal to design an aptasensor with high specificity, flexibility, and simplicity. In this work, we develop a strategy of triblock DNA probe, which consists of two DNA probes at both ends and ployA fragments in the middle as probe-polyA-probe. PolyA fragment has high affinity to the surface of gold electrode, so it can be assembled on the electrode surface via polyA instead of traditional Au-S bonds. When the target DNA is simultaneously hybridized with the two capture probes, the hybridization stability can be improved due to the strong base stacking effect. [Ru(NH 3) 6 ]3+, as signal probe, can be electrostatically adsorbed on the negatively charged DNA skeleton. A wide linear range (10 pM-10 μM) is obtained with a detection limit of 2.9 pM. Our electrochemical aptasensor has good repeatability, stability, and specificity. More importantly, the electrochemical sensor can successfully detect DNA in human serum samples, which proves its practical value and extensive applicability in complex environment. [ABSTRACT FROM AUTHOR]