Degree
Doctor of Philosophy (PhD)
Department
Chemistry
Document Type
Dissertation
Abstract
My dissertation describes the design and synthesis of a novel photoswitchable rotaxane-based molecular platform to modulate lipid membranes in response to light. Furthermore, the ability of this system to alter lipid bilayer properties is leveraged to study the neuromorphic behavior of lipid membranes and to assess their potential as membrane-targeted antibacterial agents.
Chapter 1 explores the significance of rotaxanes as a next-generation molecular platform for membrane modulation and highlights their unique structural features and potential functional capabilities compared with established systems.
Chapter 2 describes the synthesis of a rotaxane featuring a macrocycle with appended photoswitches, together with its photoswitching behavior in solution and in model lipid bilayers. Supported by molecular dynamics simulations, this work provides insight into how the rotaxane interacts with surrounding lipids and how photoswitching alter lipid packing and membrane permeability. Importantly, incorporation of photoswitches into the topologically constrained architecture of the rotaxane did not adversely affect their photophysical properties.
Chapter 3 examines how rotaxane photoswitching affects the permeability of lipid bilayers with different compositions and fluidities. It establishes membrane composition and fluidity benchmarks for vesicles whose permeability can be reversibly controlled by azobenzene-decorated rotaxanes, enabling the release of hydrophilic cargo. The chapter also identifies the roles of individual rotaxane components in light-driven permeability changes, providing design principles for more effective rotaxane-based membrane modulators.
Chapter 4 demonstrates that photoswitchable rotaxanes can reversibly modulate neuromorphic behavior in lipid membranes. Specifically, photoisomerization switches the membrane between a memristive state, dominated by voltage-dependent ion transport arising from increased membrane permeability, and a memcapacitive state characterized by charge accumulation across the bilayer. Overall, this work establishes a new strategy to emulate the history-dependent electrical behavior of neural synapses, suggesting that photoswitchable rotaxanes embedded in membranes could serve as promising components for bioinspired neuromorphic devices.
Chapter 5 introduces rotaxanes as potent antibacterial agents against Acinetobacter baumannii, a highly virulent, multidrug-resistant pathogen. This chapter also establishes preliminary structure–activity relationships, providing insight into how individual rotaxane subcomponents contribute to antibacterial activity. Furthermore, the results suggest a membrane-active mechanism of action, although more detailed studies will be required to fully elucidate the underlying antibacterial mechanism.
Date
7-12-2026
Recommended Citation
Conthagamage, Udyogi Navodya Kulathilaka, "Functional Rotaxanes in Lipid Membranes: From Photoswitchable Membrane Modulation to Ion Transport, Neuromorphic Behavior, and Antibacterial Activity" (2026). LSU Doctoral Dissertations. 7134.
https://repository.lsu.edu/gradschool_dissertations/7134
Committee Chair
Victor García-López
LSU Acknowledgement
1
LSU Accessibility Acknowledgment
1