Date of Award
Doctor of Philosophy (PhD)
Biomedical and Chemical Engineering
Chemical Engineering | Engineering
Shape-memory polymers (SMPs) are a class of smart materials that can respond to stimuli. A one-way SMP can transform from a temporary shape to a permanent one. Taking advantage of their active response and deformation properties, SMPs have been studied for a variety of applications. Despite the extensive study on SMPs, significant challenges to their successful application in biomedical science still need to be addressed. For instance, although many studies have researched diverse shape-memory triggers as well as multi-shape memory (such as triple-shape memory and two-way SMPs), there has been almost no study of cytocompatible, non-thermally triggered, multi-shape change SMP, further limiting their applications in biomedicine. Furthermore, most SMPs used in biomedical research are synthesized at the macroscale, restricting their use in applications such as drug delivery. An additional limitation is the lack of biological coatings capable of enhancing SMP cytocompatibility or bioactivity. Scaling down to the micro/nano scale to address these issues is limited by currently available methods of synthesis. Previously, these topics have been studied independently, in isolation; in this thesis, in the interests of broadening the triggering and shape change mechanisms available to biomedical researchers, these concepts are integrated in a novel way. In the following subsections, each of these building blocks will be addressed independently, and the relationship between each will be systematically enlightened. First, this dissertation describes the development of a cytocompatible SMP that responds directly to cells (Chapter 2). Shape recovery in response to hepatic cells in the presence of heparin was successfully demonstrated. We envision using cell-responsive materials and phenomena in biomedical fields, expanding the range of SMP-triggering mechanisms to include biological cells. Next, this dissertation describes a triple-SMP that, with cells present, can undergo two different shape changes via two distinct cytocompatible triggers during active cell culture (Chapter 3). Tandem triggering was achieved via a photothermally triggered component, comprising poly(ε-caprolactone) (PCL) fibers with graphene oxide (GO) particles physically attached, embedded in a thermally triggered component, comprising a tert-butyl acrylate-butyl acrylate (tBA-BA) matrix. This development can be anticipated to enable the incorporation of triple-shape memory into biomedical devices and strategies. Then, Chapter 4 of this dissertation describes the in situ fabrication and application of a human body temperature-triggered nanoscale SMP. The SMP NPs at their original shape exhibited reduced toxicity and enhanced cellular uptake towards homotypic cells. This innovative approach revealed a promising potential for cell membrane coating applications, as well as a novel method for targeted drug delivery of nanosized SMPs. Finally, Chapter 5 of this dissertation describes the cell-mediated polymerization of a fluorescent polymer (PNaSS) without the addition of initiator or ultraviolet illumination. Collectively, this dissertation addresses in situ polymerization of nanosized SMPs, a biological triggering mechanism, and a triple-SMP for biomedical applications.
Chen, Junjiang, "Cytocompatible Functional Polymers: In Situ Synthesis, Novel Triggering, and Multistep Actuation" (2023). Dissertations - ALL. 1734.