Doctor of Philosophy
Dr. Peter R. Norton
The spatial control of cellular adhesion is fundamental to the development of studies of cell interaction, cellular microarrays, and cell based biosensors. The ability to pattern cell adhesion on flat substrates and in microfluidic channels is important for locating cell near microdetectors in cell based biosensor devices. Cell adhesion can be controlled by patterning a material's wettability, as cells are able to adhere to hydrophilic surface and will generally avoid hydrophobic materials.
This thesis focuses on patterning the surface wettability of poly(dimethylsilox-ane) (PDMS) in order to spatially control cell adhesion. The polymer is selectively modifed by the deposition of aluminum through a stencil mask in a magnetron sputtering system. After etching away the aluminum layer, a hydrophilic oxygen rich silica-like layer is exposed. This technique permits the creation of hydrophilic dots which are surrounded by the hydrophobic native PDMS. A second technique involving the use of photolithography results in a surface that can undergo hydrophobic recovery. By contrast, the selected areas covered by aluminum are protected against hydrophobic recovery. Finally, photolithography is used to selectively react a methyl terminated alkyl silane with the modified surface.
Each surface modification was characterized by X-ray photoelectron spectros-copy, atomic force microscopy, contact angle measurements, force distance curves, cell attachment and viability tests; the effectiveness of the techniques to pattern wettability and cell adhesion was assessed. The relative adsorption of fibronectin and fibrinogen was visualized on the patterned surface. Further, the relative availability of the cell binding sites were also visualized on the surface through immunofluorescent labeling.
While all patterning methods were effective at controlling surface wettability, cells did not show any selectivity on the surfaces patterned for hydrophobic recovery. The use of an alkyl silane proved more effective, as cell attachment did show some selectivity. However, cells were able to adhere and grow on the hydrophobic silanized regions. The stencil mask patterned surfaces showed cell selectivity, with cells almost completely avoiding the native hydrophobic PDMS background.
Overall, the stencil mask patterning technique proved to be the most effective at controlling cell adhesion. Thus this surface patterning technique was integrated into reversibly and irreversible sealed microfluidic channels.
Dechene, Jessica M., "Surface Modifications of Poly(dimethylsiloxane) for Biological Application of Microfluidic Devices" (2010). Electronic Thesis and Dissertation Repository. 24.