Graduation Semester and Year

2011

Language

English

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Bioengineering

First Advisor

Young-Tae Kim

Abstract

The mechanical properties of the cellular environment play an important role in the functioning of the cell. Cells attach to the extracellular matrix or other surrounding cells, thus sensing their mechanical properties and tune their own internal mechanical properties accordingly. A number of in vitro studies have been performed to study various cellular mechanical phenomena, but most of them employ a very stiff substrate such as glass or plastic that does not encompass the physiologically relevant range. Also, for tissues of the nervous system, the relationship between the substrate stiffness and the cellular behavior is less understood. In this study, we report the fabrication of a novel device having a cell growing substrate with adjustable elastic moduli ranging from 20kPa to 2.2MPa and systematically study the effects of substrate elasticity on cell behavior. The substrate can be further tuned to obtain a wider range of moduli for the intended applications. Also, the substrate has a thickness of 50 µm which is suitable for monitoring the cells at high magnifications. To study the effects of the varying stiffness on cell behavior, mouse neural stem cells, rat embryo derived cortical neurons, and human glioblastoma multiforme cells were cultured on these devices and monitored. We observed a significant difference in the outgrowth, differentiation, and migration of these cells based on the stiffness of the substrates, indicating that cells respond differently to substrate stiffness. For NSCs, it was seen that there was an increase in the proliferation and differentiation of these cells into astrocytes with increase in the substrate stiffness. Cortical neurons displayed increased outgrowth with stiffer substrates whereas for GBM too, migration of the cell from their clusters was seen to increase with the underlying substrate stiffness. In order to further improve the efficiency of the device and study two or more factors that could affect cell behavior simultaneously, a PDMS array has been fabricated having substrates of different stiffness, assembled on a 48X65 mm glass slide and coated with different ECM proteins. Human gliobastoma multiforme cells were cultured on the array to examine the effects of both the stiffness and the underlying ECM protein at the same time and it was observed that substrate stiffness strongly controlled cell migration for majority of the coated proteins. In conclusion, the device/array can be easily tuned for making substrates of varying stiffness over the entire physiologically relevant range on a single glass slide to mimic the in vivo substrate of the cells and to test cellular behavior on the differing substrates.

Disciplines

Biomedical Engineering and Bioengineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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