Date of Award

Spring 2006

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Engineering

First Advisor

Debasish Kuila

Abstract

The extracellular matrix (ECM) plays an important role in regulating a number of cellular properties and functions like cell differentiation, cell synthesis and degradation, cell viability and proliferation, cell function, and cell aging. Surface modification of planar substrates with self-assembled monolayers (SAMs) is a promising technique to achieve stable ECMs.

In this work, substrates such as silicon (Si), gallium arsenide (GaAs) and indium tin oxide (ITO) substrates were modified with SAMS containing amino (-NH2), methyl (-CH3), thiol (-SH) and carboxylic (-COOH) end groups and characterized using contact angle measurements, surface infrared (IR) spectroscopy and atomic force microscopy (AFM). Different cell types such as human dermal fibroblasts (HDFs), mouse stromal mesenchymal stem cells (MSCs), rat brain neurons (RBN), and rat hepatocytes were cultured on these surfaces to develop stable and standard cell culture platforms (CCPs).

Contact angle measurements showed that surfaces modified with SAMs containing amino and carboxylic end groups are hydrophilic, methyl terminal group is hydrophobic, and SAM containing thiol end group has an intermediate property. Reflection absorption infrared spectroscopy (RAIRS) and attenuated total reflectance IR (ATR/IR) confirmed the presence of respective SAMs on surfaces. AFM data show that SAMs with methyl and carboxylic group modified surfaces present an average roughness of 1.51 and 2.67 nm, which are higher than 1.01 and 1.1 nm obtained for SAMs containing amino and thiol end groups.

For cell culture studies on SAM-modified surfaces, viability was assessed using the LIVE/DEAD® assay, proliferation by the MTT assay, while phenotypic maintenance was monitored by immuohistochemical detection of Type I collagen. Morphological responses of the cells were studied using phase contrast and fluorescence imaging to document changes in cell shape and properties. Based on their viability, proliferation and phenotype, HDF cells preferred the substrates in the following order: ITO-ODT > Si-APTES > ITO > Si > GaAs-ODT > GaAs. MSCs grew well on all SAM-modified surfaces with highest proliferation observed on thiol (-SH) terminated ITO substrates. For neuronal cells, addition of 1% serum initially to the cell suspension maintained their viability on methyl and amino modified ITO substrates by neutralizing the effects of dimethyl sulfoxide (DMSO). Neurons preferred amino over methyl terminated SAMs on ITO. (Abstract shortened by UMI.)

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