Nanowires in Cell Biology
Abstract: This thesis explores the interactions between cells and nanowires, to increase our understanding of how cells are affected and how they can be manipulated by these one-dimensional, semiconductor crystals (lengths 1-10 µm, diameters <100 nm). These are much smaller than most mammalian cells (10-30 µm in diameter), and it is generally held that nanowires can be interfaced with cells without adverse effects. On this assumption, several nanowire-based applications have been explored, yet few studies investigate how basic cellular functions are affected. We have studied how the dimensions of nanowires affect fundamental cell behaviour in cells. We found that increasing nanowire length reduces cell migration and interferes with cell division. Cells interfaced with as few as 50 nanowires are inhibited in their migration. Increasing the density of nanowires has minor effects on migration and division until a threshold density is reached when the cells are able to adhere to the tips of the nanowires rather than the substrate, enabling migration. Based on these results, we hypothesize that it is possible to tune nanowire dimensions to control the degree of cell migration and proliferation, enabling experiments where cells are immobilized for continuous observation over several generations. Our results can further be used to limit adverse effects in nanowire-based cell biological applications. As part of our cell-nanowire interaction studies, we have worked toward a microfluidic injection system based on oxide nanotubes to improve both existing, standard injection systems and nanowire-based experimental versions. We demonstrate the successful fabrication of key parts of this system and its fluidic transport ability, important steps toward a fully functional nanosyringe device, capable of serial injection and retrieval of cell material. To improve future studies regarding the interactions between semiconductor nanowires and cells, we developed inherently fluorescent nanowires and showed that it is possible to fabricate nanowires with alternating fluorescent and non-fluorescent segments, creating a barcode design useful for systematic studies. These results will prove useful for research groups working towards cell biological applications based on similar nanostructures, both for injections, cell migration and otherwise.
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