DISSERTATION

_____________________________________________________________ Results and Discussion
Figure 3.55. FSCV recorded for a ssDNA/MCU (grey line) and dsDNA/MCU-modified
electrode before (black line) and after intercalation with AO-GOx into the dsDNA (green
line). FSCV measurements were conducted in 10 mM PB solution containing 450 mM
K2SO4 with a 1 V/s scan rate. DNA immobilization and subsequent passivation were
performed by potential-assisted immobilization (0.5/-0.2 V vs. Ag/AgCl/3 M KCl pulse
profile with 10 ms pulse duration), each for 1 min. Immobilization was performed in 1
µM DNA solution in 10 mM PB with 450 mM K2SO4. Passivation was performed with 1
mM MCU in 10 mM PB with 20 mM K2SO4 (30 % ethanol). Hybridization was done by
incubation for 10 min in 1 µM Fc-tDNA solution in 10 mM PB with 450 mM K2SO4 at 37
°C. Intercalation was performed by drop coating of an aliquot of an AO-GOx solution (in
100 mM PB) on the dsDNA/MCU-modified electrode (incubation time: 15 min).
Figure 3.56 shows the possibility to clearly differentiate between dsDNA and ssDNA-modified
electrodes via AO-GOx intercalation using the developed DNA detection scheme based on
potential-assisted surface modification to control the ssDNA coverage and the passivation of
the surface. Normalized steady state currents with respect to dsDNA-modified electrodes are
extracted from I-t curves after the addition of glucose (40 mM) measured with ssDNA and
dsDNA-modified electrodes. After removal of tDNA and AO-GOx the electrodes were again
incubated in the AO-GOx solution and the amperometric measurement was repeated in order
to investigate the interaction of the AO-GOx with ssDNA (negative control). Higher currents
3.5 Intercalation as a DNA detection technique 102