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Abstract
Traditional ways for the determination of the transcription factor, which include Western blots, gel-shift assays, and quantitative polymerase chain reactions, are time-consuming and complex. Here, a simple, electrochemical biosensor for the determination of transcript nuclear factor kappa B (NF-κB) is reported. By incorporation of the NF-κB binding sequence and a hemin initiated DNA structure switch, a dual functional probe that adopts the stem-loop structure was immobilized on the surface of gold electrode. With the binding of NF-κB, the probe was protected from digestion by λ-exonuclease. The stem-loop structure of the probe was maintained and the DNA nanostructure cannot capture hemins. No electrochemical signal was produced in this state. Without binding of NF-κB, the probe was digested by λ-exonuclease. The loop region of the probe was liberated and changed its structure to G-quadruplex with hemin in the center, generating an electrochemical signal. As a result, sensitive determination of NF-κB was achieved with a limit of detection of 0.2 nM.