Electron beam lithography: a promising and versatile technique for fabrication of new platforms for cell studies
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- Institutt for fysikk 
For more than a century cellular studies using cell cultures have had an immense impact on biomedical research. These in vitro studies have primarily been performed on cultures of cells residing on flat two-dimensional surfaces. However, cells in tissue are embedded in a more complex three-dimensional network providing biochemical and biophysical cues, which support the cells in their growth and function. Flat surfaces are therefore only partially representing the conditions cells experience in vivo. Recently, modern nanotechnology tools have made us able to recreate some of these in vivo characteristics in an in vitro setting. Furthermore, the techniques have facilitated the creation of systems for advanced cell studies and sophisticated applications in smart bio-devices. By employing nanofabrication techniques, for instance lithography adopted from the semiconductor industry, it is now possible to fabricate more complex substrates for cellular studies, taking cell studies to the next dimension. One approach for fabricating substrates for these studies is applying electron beam lithography to make vertically aligned nanostructures. Accordingly, the main purpose of this work has been to develop a fabrication protocol for fabricating nanostructures in an epoxy based polymer. Micrometer thick films of the polymer SU-8 were spin coated on standard microscopy cover-glasses. By exposing given areas of the resist to electrons, structures with controlled nanoscale dimensions were realised. As the structures were fabricated directly on transparent substrates, they could be easily be studied with optical microscopy techniques used in the life sciences. The samples were then used to study the migration dynamics of fibroblast cells on surfaces covered with nanostructures. More specifically, distinct regimes for migration of fibroblasts were identified on different arrays of vertically aligned, hexagonally organised pillars. These findings were corroborated with detailed dynamic studies on the influence of the nanopillars on the actin cytoskeleton. From these dynamic studies, the cells were found to interact strongly with the pillars, and this interaction was identified as a contribution in reducing the migration speed on specific pillar arrays. In another cell line, electron beam lithography-fabricated surfaces were used to study the actin cytoskeleton and focal adhesion organisation in response to a set of nano-topographies. As a model system, different arrays of vertical nanopillars were fabricated. Using high resolution optical microscopy, the cells were found to respond differently depending on the type of nanopillar arrays. The work presented in this thesis shows how electron beam lithography can be utilised to fabricate surfaces decorated with nanostructures for cellular studies. In a broader sense, the work contributes to understanding design of new surfaces for cellular studies, how to make smarter bio-interfaces; and at last, understanding mechanisms associated with cells interacting with nanostructures.