DISSERTATION

_____________________________________________________________ Results and Discussion
In order to perform the experimental sequence as explained in Figure 3.53, the possibility of
removal of the intercalating compound was tested using the ssDNA/MCU-modified electrode.
Upon incubation with AO-GOx, a chronoamperometric measurement was performed in
phosphate buffer containing the redox mediator (ferricyanide, 1 mM) by applying a potential
of +400 mV (vs. Ag/AgCl/3 M KCl). A small interaction of the intercalator with the
ssDNA/MCU modified electrode was detected, shown in Figure 3.54 as a catalytic current upon
addition of glucose. Afterwards the electrode was treated with ethanol and water to remove
unspecifically bound intercalator and the chronoamperometric measurement was repeated. The
absence of any catalytic current upon addition of glucose in this case indicates that the
intercalator was completely removed from the surface.
Figure 3.54. Chronoamperometry with a ssDNA/MCU-modified electrode a) after
incubation with AO-GOx for 15 min, and b) after removal of AO-GOx. A potential of
+400 mV (vs. Ag/AgCl/3 M KCl) was applied; 10 mM PB containing 450 mM K2SO4 and
1 mM ferricyanide. Glucose was injected as shown on the figure.
Furthermore, to investigate how the intercalation process influences the stability of the formed
double helix, a control experiment was performed by following each step of the assay by means
of FSCV. Namely, initial hybridization of the ssDNA/MCU electrode was performed using FctDNA
and subsequent intercalation was done by leaving the labelled tDNA on the surface.
FSCV does not show any significant change in the response after intercalation, except of a small
shift of the oxidation peak. The DNA coverage remains unchanged suggesting that the
intercalation process does not impede the stability of the double helix (Figure 3.55).
3.5 Intercalation as a DNA detection technique 101