Micro-scale Platforms for Investigations of Biological Structures

Sammanfattning: This thesis describes the development of innovative micro-scale platforms as a means to address the current challenges within the field of cell biology, and to provide an interface between miniaturized analytical technology and experimental systems for the life sciences. The work includes an analytical platform for rapid assessment of the viability of adherent single cells; a surface patterning strategy for investigations of cell-to-cell communication via protrusions; a versatile microfluidic probe in SU-8 hard-polymer, and a microfabricated millimeter-wave measurement system for the identification and characterization of niosome (non-ionic surfactant vesicle) constituents, which is operated in a label-free, non-invasive manner.

One of the major challenges in cell biology is to understand the heterogeneity of cells, i.e., cells of the same species and in the same local environment can differ dramatically. Recent evidence suggests that these differences in individual cells can affect the development, health and function of the entire cell population, and for this reason, single-cell studies have become increasingly important. However, there remains a need of instrumentation for efficient analytical investigations on single cells in adherent cultures and tissue slices.

My thesis addresses some of the research problems that life scientists encounter in single-cell experiments, and suggests novel analytical devices and protocols that provide efficient solutions to these problems. One of them is a protocol for the rapid determination of the viability of individual mammalian cells in adherent cell cultures, utilizing a microfluidic device for selective perfusion of targeted cells (Paper I).

I also introduce micropatterned cytophobic polymer (Teflon AF) on glass as cell culture substrate, which exhibits differential adhesion properties with respect to biological cells. This enabled the analysis of spatially separated cells in terms of their ability to establish interconnections by reaching out to other cells via protrusions, guided by the pre-determined surface pattern. Applying a microfluidic device for selective perfusion of single cells grown on these substrates allowed for examination of the chemical communication between interconnected pairs of cells (Paper II).

In Paper III, a facile process for fabrication of free-standing microfluidic devices in a photo-patternable hard-polymer (SU-8) is reported. This constitutes a major, necessary step towards large-scale fabrication of diversely functionalized single-cell superfusion devices with high potential in drug screening and diagnostics.

Finally, in Paper IV, a concept for an open-volume dielectric spectroscopy platform based on millimeter-wave technology, developed for label-free identification and characterization of niosome constituents, is presented. The microfabricated platform creates new opportunities for analyzing and characterizing the compositional variances in niosome membranes in the context of drug delivery.