Date of Award

8-4-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical and Chemical Engineering

Advisor(s)

Mary Beth Monroe

Abstract

Shape memory polymers (SMPs) are a class of smart materials that can maintain their secondary shape after implantation. Upon exposure to specific external stimulus (such as heat, enzyme, magnetic field, light, and pH) they recover their primary shape to serve as indication tool, drug/antibiotic delivery device, antifouling surface, and/or sensor. In the second chapter of this dissertation, synthesis of a library of biostable segmented shape memory polyurethanes with varying hard/soft segment ratios is synthesized and extensively characterized in varying degradation media. Shape recovery and mass loss were negligible over long time frames of storage in accelerated degradation media for polyurethanes with higher ratios of hard segment. In this research magnetic particles were incorporated into the polymer to enable a shape change response to magnetic field, which resulted in 44% recovery after 5 minutes of exposure. In the third chapter, chemical and physical methods of incorporation were utilized to couple non-drug antimicrobials into this biostable polymer. Thermomechanical, shape memory, and growth inhibition rates against E. coli and S. aureus were assessed over time. This platform can be coupled with other stimulus responsive moieties to act as a self-defensive material for user-defined triggering in biomedical applications to prevent antibiotic overuse and antibiotic-resistant bacteria development. In the fourth chapter, polyglutamic acid was incorporated into the biostable polymer backbone to provide an enzymatically responsive SMP for infection surveillance and treatment in chronic wounds. This SMP changes shape specifically in the presence of bacterial proteases; and minimal recovery was observed in response to mammalian cells and other control media. Visible shape recovery of these SMPs in both in vitro and ex vivo models indicate the potential to use this system to alert clinicians to start antibiotic treatment; and inhibition of biofilm formation on SMP surfaces after shape recovery could sensitize bacteria to applied treatments.

Access

Open Access

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