an appropriate conformation, which is close to the physiological conformation
of these molecules [49]. Although the influence of the surface
chemistry on the cell adhesion is abundant in the literature, the discussion
on the effect of the layer stability is very limited. The results on the
sample CPA42 showed how crucial is the layer stability for a normal cell
behaviour. Moreover, the live monitoring of the cell behaviour was rarely
performed and the cell viability on different surfaces was generally
estimated from assays or static single images. Since CCHM enables
label-free and quantitative live cell imaging (see Supporting Information,
video file), it should be considered as an essential technique for
the monitoring of biological reaction of cells to both layer stability and
its chemistry.
The deposition of amine coating by plasma polymerization appeared
to be an efficient environment friendly method for the preparation of
nitrogen-rich biocompatible coatings favouring the adhesion and proliferation
of human fibroblasts. Nevertheless, the conditions of plasma polymerization
must be carefully tuned to obtain a sufficient amine
concentration combined with good layer stability in water. The high
plasma power leading to deposition of more compacted films induced
not only depletion of NHx environment but led also to layer buckling induced
by contact with water. Such negative effect of plasma power was
shown before [22] but requires further analysis to investigate the mechanism
of CPA plasma polymer cracking.
4. Conclusion
The plasma polymerization of cyclopropylamine in RF discharge was
used as a versatile method for the deposition of thin amine coatings on
glass with different concentrations of nitrogen and NHx groups. Although
the surface chemistry can be considered as a crucial parameter,
the stability of layers in water strongly affected their biocompatibility.
The film with the lowest nitrogen concentration, deposited in the continuous
wave mode, cracked when immersed in water. It had detrimental
effect on the cell behaviour. Although the films deposited in the
pulsed mode were slightly dissolved in water, their morphology
did not change and the cells behaved normally. The results from
the analysis of human dermal fibroblasts viability by CCHM were
correlated with the surface chemistry of the films. It was proved
that amine-rich coatings prepared in pulsed plasma are biocompatible
and a higher concentration of amine groups at the surface
enhances the cell adhesion and proliferation. In the analysis, CCHM
played an important role as a reliable technique for monitoring and
evaluation of cell–surface interaction without the need of staining
and additional sample preparation.
Acknowledgements
This work was supported by CEITEC — Central European Institute of
Technology (CZ.1.05/1.1.00/02.0068) from the European Regional
Development Fund, by the Specific Research grant of Brno University
of Technology (FSI/STI-J-15-2752), and by BioFibPlas project No.