DISSERTATION

________________________________________________________________ Experimental Work
of the labeled or non-labeled target DNA solution (1 μM in 10 mM PB, 450 mM K2SO4) and
kept in a thermo-mixer (HTC BioTech, Germany) at 37 ºC for 10 min or 1 h. The electrode was
sealed within the tube to prevent solution evaporation. After hybridization the electrode was
rinsed with the hybridization buffer to remove any unspecifically bound tDNA.
Dehybridization of dsDNA was performed by incubation of the dsDNA/thiol electrode in water
for 5-10 min. The efficiency of dehybridization was confirmed using Fc-tDNA by measuring
the Fc redox peak before and after dehybridization using fast-scan cyclic voltammetry.
5.10.1 Detection of hybridization
Direct hybridization detection was done using different detection methods, depending whether
the tDNA was labeled or not. Hybridization with non-labeled tDNA was detected by means of
EIS following the change of Rct upon hybridization. EIS parameters were the same as in Section
5.9.1.
Hybridization with labeled tDNA was detected using FSCV in 10 mM PB with 450 mM K2SO4
at a scan rate of 1 V/s in the potential window from -0.05 V to 0.55 V (vs. Ag/AgCl/3 M KCl)
under argon atmosphere.
5.10.2 DNA coverage determination by means of FSCV
Direct determination of tDNA coverage or indirect determination of pDNA coverage (in case
of low coverages) was done by integration of the cathodic peak of the Fc label from FSCV
measurements. The cathodic peak area can be used to calculate the transferred charge:
Q =
peak area
ν
(5.7)
where peak area is the background corrected charge under the cathodic wave and v is the scan
rate used in the FSCV measurement. Then the surface coverage can be calculated:
Γ =
Q
nFA
(5.8)
where n is the number of electrons transferred in the redox process (in this case 4 since four
ferrocene moieties were used per DNA strand), F is the Faraday constant (96485 C/mol) and A
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