Dissertation/Thesis Abstract

Surface and Colloidal Approach to Endothelial Cell-Segmental Polyurethane Interactions
by Hill, Michael J., Ph.D., State University of New York at Buffalo, 2017, 250; 10254911
Abstract (Summary)

The field of biosurface science began the wide scale investigation of the adhesive interactions between cells and materials in the 1960’s. This occurred shortly after the emergence of several empirical or theoretical approaches to relate liquid contact angle and wettability to solid surface energy. These theories, along with the famous DLVO theory of colloidal stability have been applied extensively to study the aqueous stability and adhesive interactions of cells and other biological substances. However no definitive statement about the intermolecular force nature of these interactions is widely accepted today.

In this work we investigated the adhesive relations between endothelial cells and segmental polyurethanes. Endothelial cells are a highly important cell type for regenerative medicine applications. Additionally, segmental polyurethanes have been used extensively as biomaterials and have several applications as support structures for endothelial cells. However, the relationship between chemical structure of the polyurethane, its resultant physical structure after processing, and the character of the surface molecular force field that interfaces with biological proteins and cells is still obscure.

We applied several of the original surface and colloidal theories as well as some of their more modern updates to investigate the nature of the relationships between polyurethane chemical structure, surface energy, and the behavior of endothelial cells in contact with them. We investigated a 2D (surface) context where cells interact with a thin segmental polyurethane film consisting of a polycaprolactone soft segment and an L-tyrosine based chain extender with aliphatic diisocyanate. We also examined the interfacial characteristics of different protein matrices which act as interlayers between endothelial cells and the polyurethane substratum. Lastly, the 3D (colloidal) context of bimodal microtissues consisting of endothelial cells or epithelial cancer cells interacting with polyurethane microgel particles with poly (ethylene glycol) soft-segment in bulk tissue phases was also investigated. The altered surface chemistry of cancer cells has been widely acknowledged and serves as a useful comparison to endothelial cell microtissue behavior in the search for general relationships.

This family of segmental polyurethanes has previously been shown to influence the differentiation of mesenchymal stem cells. Therefore, considering the controversies surrounding surface energy theory, we sought empirical relationships to correlate cell behavior to the surface energy of a biomedically useful system of polymers which is to be distinguished from relationships which may be found for certain homogenous or “ideal” surface systems that have been highly controlled. Such “ideal” systems may be artificial in terms of design parameters for practical biomedical usage considering the real world surface heterogeneity, which is ubiquitous.

We found that for a given system, each theory can offer unique interpretations and “extra” information. However, different systems were best suited to different theories. In brief, Kaelble’s numerical method (Owens-Wendt) best predicted substratum polarity, van Oss-Good-Chaudhury theory best predicted protein-endothelial cell interactions, and the critical surface tension of Zisman best predicted hydrated polyurethane microgel-cell interactions in conjunction with the extended DLVO theory. We suggested that the success or failure of a given theory for a particular system may stem from differences in microscopic detail that aren’t accounted for. Overall, a combinatorial surface energy approach was useful in comparing physically disparate cellpolyurethane interaction contexts.

Indexing (document details)
Advisor: Sarkar, Debanjan
Commitee: Baier, Robert E., Ehrensberger, Mark, Lovell, Jonathan
School: State University of New York at Buffalo
Department: Biomedical Engineering
School Location: United States -- New York
Source: DAI-B 78/07(E), Dissertation Abstracts International
Subjects: Physical chemistry, Biomedical engineering, Biophysics
Keywords: Colloid, DLVO, Endothelial, Polyurethane, Surface, vOGCT
Publication Number: 10254911
ISBN: 9781369593273
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