DISSERTATION

_________________________________________________________________ Aims of the Work
Self-assembly finds its application in many different fields of research, yet the most
used protocol is the same in all of them – simple immersion of the material of choice into a
solution containing the molecule to be assembled, followed by a spontaneous adsorption and
formation of appropriate bonds 66 . Among SAMs self-assembly of thiolated molecules on gold
is the most known.
While, for example, the aim of SAM formation of alkylthiols is generally to reach highly
compact monolayers, the immobilization of thiolated DNA is performed aiming at a wide range
of DNA coverages, depending on the envisaged sensing strategy. Nevertheless, in order to
obtain high coverages of thiolated molecules a long incubation time is required, ranging from
several hours to days 13-15 . In contrast, low coverages can be obtained in a shorter time, however,
with a significant variation of densities and substantially decreased reproducibility 67 .
To meet the demands of the market, future point-of-care devices have to link high-quality
performance with speed, simplicity and low production costs 4 . Despite its simplicity of
formation of comparably stable films, thiol chemisorption on gold is not yet the chemistry of
choice for fabrication of commercial DNA biosensors, partly due to issues with reproducibility
and the time required for modification. In order to profit from possibilities that self-assembly
offers, the dependence on the spontaneous adsorption process, that is very slow and lacks
reproducibility, needs to be eliminated. A new and simple strategy that will allow to
reproducibly control the surface modification in a desired manner, and what is equally
important, in a very short time, would significantly decrease the production costs and with this
the cost of a final point-of-care device.
Base-by-base DNA sequence synthesis made a tremendous contribution to fabrication of highly
dense DNA chips for genome sequencing. However, the complex nature of chemical synthesis
and very expensive production, coupled with a limited flexibility for customization and length
of probe sequences, makes this technique less suitable for point-of-care devices 51 . Moreover,
the very high number of individual test sites is often not necessary for specific measurements
of point-of-care applications. Furthermore, the more flexible and cheaper approach, namely
spotting of pre-synthesized DNA sequences, still suffers from several drawbacks, such as
special working conditions and problems with accuracy and efficiency. Nevertheless, new
approaches for the production of DNA chips are arising, including electrochemically driven
surface modification, demonstrating the evolution of microarray technology to more practical
platforms for diagnostic applications.
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