DISSERTATION

_____________________________________________________________ Results and Discussion
3.3.1 Fast and controlled formation of DNA surfaces. Optimization of ssDNA
immobilization procedure
Theoretical discussions were done with Dr. Magdalena Gebala and Prof. Dr. Fabio La Mantia.
Parts of this section were published in ref. 5 : “D. Jambrec, M. Gebala, F. La Mantia, W.
Schuhmann, Angew. Chem. Int. Ed. 2015, 54, 15064-15068; Angew. Chem. 2015, 127, 15278-
15283.” written by the author. Figure adapted from ref. 5 .
The amount and accessibility of immobilized ssDNA on the electrode surface greatly influences
the later hybridization process. Therefore, well-defined reproducible and controlled DNAmodified
surfaces are a prerequisite for the development of optimized DNA sensors 3 . Even
though ssDNA-modified surfaces are the foundation for all envisaged applications, the
mechanism of ssDNA immobilization has not been fully elucidated yet. DNA immobilization
is a complex process depending on many parameters such as ionic strength, strand length, and
the valence of the ions screening the charge of the DNA strands 86 . By introducing varying
applied potentials, this process becomes even more complex. While it is known that certain
potentials (positive or negative with respect of the pzc) induce the bending or lifting of DNA at
the electrified interfaces, the reasoning that the DNA itself is attracted by a positively charged
3.3 Importance of controlling the surface 51