Label-free "digital detection" of single-molecule DNA hybridization with a single electron transistor.

Here we present a novel assay that eliminates fluorescent labels and enables "digital detection" of single-molecule DNA hybridization in complex matrixes with greatly simplified protocols. Electronic coupling of the binding state of a single oligonucleotide to the quantum dot (QD) of a single electron transistor (SET) affords direct observation of binding events in real-time via "molecular gating". The change of electrostatic charge associated with the molecular capture is used in lieu of a gate electrode to modulate the SET conductivity. Target oligos containing base mismatches do not elicit SET response under 0.1X SSC at room temperature nor do changes in ionic strength or pH. Furthermore, hybridization is detected even in optically inaccessible matrixes such as serum or quanidinium thiocyanate lysis buffer.