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