Label-free and 'signal-on' DNA detection using a probe DNA terminated with ferrocene and -cyclodextrin

A novel oligonucleotide probe was designed to provide a self-reporting 'signal-on' DNA detection. The probe was terminated with a ferrocene moiety at one end and a -cyclodextrin moiety at the other end, as the signal-generating and signal-suppressing parts, respectively. Electrochemical measurement of the probe using a carbon-based interdigitated array microelectrode chip showed a sigmoidal current-potential curve in the absence of the target oligonucleotide complementary to the probe. In the presence of the target, however, the curve shifted towards a more negative potential (62mV) and the observed current at +0.3V was increased 5.2-fold, indicating that the probe provided a 'signal-on' response upon hybridisation. This probe achieves simple DNA detection without the need to label the target oligonucleotides or to add any other electroactive reagents to the measurement system.