DISSERTATION

______________________________________________________________________ Introduction
length of the DNA. On average, for sequences with 25 bases, around 100 masks are needed per
chip. Nevertheless, the obtained chips can have an extremely high density (> 10 6 spots per
array). Main drawbacks of this technique are the complex nature of chemical synthesis and a
very expensive production 51 . Furthermore, difficult customization and the possibility of
synthesizing only relatively short DNA sequences are limiting the application of the technique
for production of point-of-care devices.
Figure 1.10. Schematic representation of the photolithographic synthesis of DNA
sequences on the electrode surface. a) surface modified with a covalent linker with a
protective group, b) irradiation of desired spots on the surface, c) modification of
deprotected spots with desired nucleotides, d-h) repetition of the process of irradiation
and modification with nucleotides to fabricate spots with desired DNA sequences.
The principle of spotting (printing) of already synthesized DNA sequences consists of spotting
nano- to picoliter volume drops of DNA-containing solution onto a predefined grid by a
1.3 DNA immobilization 19