Surface Modifications for Biointerfaces - Supported Lipid Bilayers and some Aspects of Microcontact Printing

Doctoral thesis, 2002

Biointerfaces engage several disciplines: physics, materials science, chemistry, biology and medicine. They are found on the surfaces of implants, tubes and tanks in the food industry or on the hull of a boat. In this work, model surfaces aimed for contact with biological systems were studied. The overall goal is to use the knowledge gained from this type of basic research in applications of more practical nature. Supported phospholipid bilayers (SPBs) are interesting in this context because they are deposited on solid surfaces where they mimic the biomembranes enclosing living cells. When vesicles of phosphatidyl-choline lipids come in contact with, for example, an SiO2 surface, they first adsorb intact and then transform into an SPB. The Quartz Crystal Microbalance with Dissipation (QCM-D) technique and Surface Plasmon Resonance (SPR) were used to study the kinetics of formation of SPBs. Also the adsorption of proteins (by QCM-D and SPR) and the attachment of cells (by microsocopy) to the SPBs were studied. The experiments revealed very little protein adsorption and no cell attachment. SPBs are thus shown to be quite non-adhesive surfaces, which can be used to produce surfaces with alternating non-adsorbing and adsorbing regions for e.g. biosensors or cell culture. A common technique for micro-patterning of large surface areas is Micro-contact Printing (.my.CP). In this work, the (undesired) transfer of stamp material to the surface during .my.CP was measured and characterised using mainly X-ray photo-electron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The material transfer to the substrate surface was found to be significantly reduced when the stamp was oxidised by UV/ozone treatment before stamping.