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. Author manuscript; available in PMC: 2013 Dec 17.
Published in final edited form as: J Am Chem Soc. 2012 Sep 10;134(37):10.1021/ja305720w. doi: 10.1021/ja305720w

Figure 1.

Figure 1

An antibody (Ab)-activated electrochemical “switch” that uses a redox-modified DNA scaffold conjugated with two antigens or epitopes and specifically triggered by bi-dentate antibody binding. The switch is composed of a single stranded DNA probe containing two identical, covalently-linked antigens (black crosses) and modified at the two ends with a redox label (MB: methylene blue) and a thiol group for convenient attachment to a gold electrode surface. In absence of the target antibody, the DNA adopts a stem-loop conformation that brings the redox label near the gold electrode thus enabling rapid electron transfer. Upon binding of the relevant cognate antibody, the DNA probe opens, which brings the redox label far from the electrode thus resulting in lower electron transfer rate and Faradaic current. By coupling recognition to a large-scale conformational change this mechanism renders the sensor largely insensitive to the non-specific adsorption that takes place when the sensor is deployed directly in complex biological samples4–6.