Surfaces with periodic nano-features : physical properties and biocompatibility
The behaviour of animal cells in vitro is affected by both the chemistry and the shape of the surface (“topography”) to which they adhere. Culturing animal cells on nanopatterns of different shape, dimensions and chemistry considerably modifies cell attachment, spreading, proliferation, migration and gene expression. This work was primarily aimed at elucidating the influence of nanopatterning on some physical properties of the substrate. The contact angle of water on nanopatterned silicon was measured, and the predicted DLVO (Derjaguin-Landau-Verweey-Overbeek) interaction between a nanopatterned silica plate and a microsphere was calculated. After the physical measurements, the silicon nanopatterns were replicated into a biocompatible polymer, and further experimental investigations of the response of biological cells to nano-pillared samples were carried out. Finally, in the last chapter a flow system was designed, in order to determine the influence of a nano-pitted interface on the initial adhesion of cells subjected to hydrodynamic forces. Surface texture has a great influence on both the wetting and the interfacial properties of the substrate. In this thesis, I show that the contact angles on nano-topographies are linked to the geometry and chemistry of the pattern by defined analytical rules. Contact angle measurements also proved that air-trapping can happen at a nanopatterned biomaterial surface. On the other hand, a SEI (Surface Element Integration) study predicts that the adhesion of a microsphere onto a plate should be strongly favoured by nanopatterned regular protrusions, and that the shape of the protrusions is a determining factor in this process. My results on cell behaviour confirm previous observations that some particular nano-patterns can inhibit the proliferation of fibroblasts in vitro. It is also shown how cell-specific this response can be, and possible explanations for this behaviour, including air-trapping at the interface, are discussed.