ORCID
0000-0003-4795-0882
Date of Award
5-3-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Shear-thinning hydrogels are a class of materials with unique rheological properties that enable them to undergo a reversible reduction in viscosity under shear stress, which allows for easy injection. The injectability of shear-thinning hydrogels is particularly important when considering their use in biomedical applications, such as drug delivery, tissue engineering, and wound healing. However, before advancing to these applications, it is crucial to evaluate the “injectability” of new shear-thinning hydrogels to avoid clogging of the needle for injection. Injectability is typically associated with determining suitable viscosity, storage/loss moduli, and other factors, such as injection force (e.g., needle length and gauge for injection), for a specific hydrogel composition. Cyclodextrin (CD)-based host-guest chemistry is a widely used method for creating functional shear-thinning hydrogels. Despite the versatility and functional group tolerance of ring-opening metathesis polymerization (ROMP), its utilization in CD-based polymer synthesis is limited. This is primarily attributed to the bulky and rigid structure of CDs, which may hinder efficient polymerization or affect the reactivity of the catalyst. In this dissertation, I describe my efforts to address issues associated with injectability of shear-thinning hydrogels by synthesizing CD-based polymers using ROMP and studying the resultant materials to establish a new approach to shear-thinning hydrogels, antibiotic-loaded coatings, and as a potential drug delivery platform. In Chapter 2, I describe a novel stimuli-responsive hydrogel comprising CD- and adamantane-based bottlebrush polymers that is both saltwater- and photoredox-responsive and exhibits broad adhesive properties on multiple materials with polar and non-polar surfaces. The host-guest cross-linked network remained soluble in deionized water and only formed viscous hydrogels in saltwater. The unique gelation mechanism was not dependent on the concentration of the polymer in the pre-gel solution, and this implies that the cross-linked network could be readily ejected from the syringe as a soluble aqueous solution prior to rapid gelation in saltwater without having to optimize any parameters associated with the injection method. The shear-thinning properties of the hydrogel were then “switched on” with either heat or exposure to visible light. Following this work, I then expanded the applications of viscous hydrogels to include antibacterial polymer coatings, which is described in Chapter 3. The polymer coatings were loaded with negatively charged antibiotics via electrostatic interactions and we demonstrated the release from the coatings effectively mitigated the growth of Pseudomonas aeruginosa. In Chapter 4, I describe an investigation into the possibility of developing a CD-based drug delivery platform through protein-polymer conjugation. In Chapter 5, future directions for “curing” the viscous hydrogels with a secondary polymerization step for further use in biomedical applications is discussed.
Language
English (en)
Chair and Committee
Jonathan Barnes
Recommended Citation
Zhang, Yipei, "Design, Synthesis, Self-Assembly, and Applications of Functional Bottlebrush Architectures through Ring-Opening Metathesis Polymerization" (2024). Arts & Sciences Electronic Theses and Dissertations. 3078.
https://openscholarship.wustl.edu/art_sci_etds/3078