Effects of Nanopillar Arrays on Cell Motility - A Study of Cell-Nanotopography Interactions
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- Institutt for fysikk 
The interplay between cells and engineered high-aspect ratio nanos- tructures is emerging as an interesting and promising field within life sciences. Specific cell responses arise as a result of interactions with these structures and can be utilized for numerous applications. This can lead to new ways of studying and manipulating biological phenomenas, at or below the spatial level of the cells themselves.The work described in this Master s thesis is based on a SU-8 nanopil- lar system previously developed at the Department of Physics, NTNU. The thesis describes how cell motility and related cell-nanotopgraphy interactions are influenced by ordered SU-8 nanopillar arrays. In par- ticular, the study focuses on the effect of nanopillar densities. Electron Beam Lithography (EBL) was applied in order to fabricate arrays of hexagonally ordered nanopillars of different densities. This was done directly on microscopy cover slips. Cells were cultured in petri dishes with nanopillar cover slips attached from the bottom. These devices are compatible with high-resolution microscopy techniques such as Confocal Laser Scanning Microscopy (CLSM), Total Internal Reflection Fluores- cence (TIRF) Microscopy and Scanning Electron Microscopy (SEM). Experiment-to-experiment independent and statistically reliable results on cell migration rates were achieved by optimizing the dimensions and arrangements of the arrays, the imaging conditions and analysis proce- dures. To capture time-lapse videos of migrating cells, CLSM was applied. In addition, CLSM, TIRF and SEM were used to characterize single-cell details related to cell motility.Quantitative analysis of NIH-3T3 fibroblast migration shows that migration rates are bi-phasic related to nanopillar density. A sharp transition occurred at the transition between arrays of 1 micro meter-interpillar spacing and 2 micro meter-interpillar spacing. Cells on high density arrays (0.75-1 micro meter interpillar-spacing) seemed to retain motility comparable to, but slightly lower than, cells on flat glass controls. The motility for cells on medium dense arrays (2-5 micro meter interpillar-spacing) was considerably restrained. These findings can be related to the specific biophysical ef- fects of nanopillars on a single-cell level. More precisely, cells adapted a suspended state (on top of the pillars) on dense arrays and a fully settled state, with pillars engulfed by the plasma membrane, on medium dense arrays. Furthermore, nanopillar/actin associations were present on all arrays, with the tightest interplay at medium dense arrays. Focal adhesion distribution has also been investigated, but was not found to have a key role in the density-dependent motile behavior.The work in this thesis reveals interesting aspects on the effects of nanotopography on cell behavior. The findings might help guide the development of devices for cell biology research which rely on cell motility control and detailed insight of the nanotopographical influence on cells.