Micro- and Nano- Engineering Cellular Patterns with Plasma Technologies.

Abstract

Plasma, not that which constitutes the flowing liquid component of blood, but that which comprises the flow of conductive ionized gas has long been a source of intrigue for physicists. Recent biomedical advances, including modification of biocompatible surfaces and the new field of “plasma” medicine are aspects of modern day plasma technology. The work described in this dissertation involved the development of two plasma-based systems that respectively utilize corona and radio frequency-generated plasma sources as modes to generate cellular patterns on polydimethylsiloxane (PDMS) surfaces in a simple, uncomplicated and convenient manner.

The first technique consisted of microfluidic device construction that permits the preferential guidance of corona along the wall of a polydimethylsiloxane (PDMS) based microfludic channel. By this means, a wettability gradient, spanning corona- treated (hydrophilic) to untreated (hydrophobic) phases, was generated on the floor of the microchannel. Subsequent and sequential application of cell repellent proteins and cell adhesion molecules allowed the assembly of a lane of rat myoblasts, along the corona treated region, adjacent to a lane of pluronic or BSA protein. As myotubes began to differentiate, a BSA coated region was degraded while a pluronic coated region remained intact and allowed for myotubes to mature to a degree sufficient enough for bulging and contraction (3 weeks was longest period for myotube survival).

In our second method, we used simple Hoffman clamps (open and closed jaw) to introduce external compression on PDMS wells, whose interiors were oxidized with a capacitively coupled r.f. plasma etcher. Due to the brittle silicate film begotten as a result of the plasma oxidation process, compression applied to the substrate resulted in the spontaneous nucleation of a v-shaped groove feature array that was aligned along the axis of compression. To demonstrate the usefulness of the apparatus, we seeded mouse embryonic stem cells (mESCs) into the grooved surfaces of the wells. We observed that the mESCs underwent transitory alignment and elongation prior to adapting a highly circular morphology after five days of culture in leukemia inhibitory factor (LIF)-enriched media.