Date of Award

December 2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical and Chemical Engineering

Advisor(s)

James H. Henderson

Second Advisor

Patrick T. Mather

Keywords

Active cell culture, Biomaterial, Multi shape memory, Shape Memory Polymer

Subject Categories

Engineering

Abstract

Biomaterial platforms have been used to probe how cells respond to chemical, topographical or mechanical changes in their environments. However, these traditionally static biomaterial platforms have not enabled the study of how cells respond to dynamic changes in their environment. Driven by a need to better understand cell behavior and its role it disease, development and tissue regeneration recent efforts have focused on designing dynamic biomaterial platforms to better mimic a cell’s natural environment. In this work, advanced shape memory polymers (SMPs) that respond to non-thermal triggers and multi-shape memory materials capable of multiple topographical transitions were developed for advanced active cell culture platforms.

The first part of this dissertation describes the fabrication and application of an enzymatically triggered SMP, which changed its shape in response to enzymatic degradation (Chapter 2). This was achieved by combining an enzymatically stable fiber and an enzymatically vulnerable fiber. Upon degradation of the enzymatically vulnerable fiber, the enzymatically stable fiber was allowed to relax back to its original conformation, thus driving shape recovery back to the original shape. Both the enzymatically triggered SMP and the process of enzymatic shape recovery were shown to be cytocompatible.

The second part of this dissertation describes the fabrication and application of visible-light triggered SMPs (Chapter 3). To design this material platform, methacrylated graphene oxide was copolymerized with tert-butyl acrylate, a material previously used in active cell culture SMP platforms. Upon exposure to white light, the graphene oxide absorbs the light energy through photoexcitation, and then transmits that energy as heat to the SMP. This heats the SMP above its glass transition temperature triggering recovery back to the original shape. In addition, visible-light triggered SMPs demonstrated localized recovery which would enable us to study cell behavioral changes as they crossed topographical boundaries.

Next, this dissertation describes the development of a real-time cell tracking algorithm that could acquire images, segment and link cell between frames and analyze cell migration behavior during a live time-lapse experiment (Chapter 4). The structure of this algorithm is discussed and one of the eight imaging modes is demonstrated during a live cell experiment.

Finally, this dissertation describes utilizing multi-shape memory composites to generate complex topographies. First, a wrinkling platform is discussed that forms double or complex wrinkle patterns along the surface of triple shape polymeric composites (Chapter 5). Second, a novel quadruple shape memory composite that displays quadruple surface shape memory is developed and discussed (Chapter 6).

Overall, this work furthers the experimental applications of SMPs as active cell culture platforms to study cell-material interactions in dynamic environments. It is expected that this work will enable new experiments probing cell mechanobiology.

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