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Dissertation
Electrodeformation in Solid-State Nanopores and its Application for Characterization of Nanoscale Vesicles and Viruses
Doctor of Philosophy (Ph.D.), Drexel University
May 2016
DOI:
https://doi.org/10.17918/etd-7797
Abstract
Cells and subcellular organelles undergo significant morphological changes in their life course, which requires crucial bending on their membranes. Therefore, characterizing the elastic properties of membranes and their deformation behavior has gained significant attention in the past decades. Researchers often use vesicles as model systems to study the mechanical properties of membranes because vesicles form the frame of various sub-cellular organelles such as lysosomes, endosomes, exosomes, as well as the lipid envelope of viruses. However, due to technological limitations, researchers have to use microscale vesicles hundreds of times larger than their naturally-occurring counterparts that are sub-micron in size. Since length-scale plays a crucial role in mechanical properties of vesicles, microscale vesicles are not a reliable model system for many biologically-relevant processes. The main objective of this research is to develop a novel analytical platform that enables measuring the elasticity of nanoscale vesicles. In order to characterize nanoscale vesicles, we employ a solid-state nanopores and an electric field to form a local strong field inside the pore. Nanoscale vesicles, dispersed in an ionic solution, are then allowed to translocate through the pore, where they undergo a strong DC pulse. Such a strong DC pulse can deform the nanoscale vesicle due to the well-known phenomenon called electrodeformation. By measuring the ionic current through the pore and blockade events caused by vesicle translocation, we characterize the morphology of the translocating vesicle. Hence, electrodeformation in nanopores allows characterizing force-deformation properties of nanoscale vesicles. In this dissertation, we focus on proof-of-the-concept experiments and particularly investigate the electrodeformation of nanoscale vesicles of varied mechanical properties. The dissertation is divided into five chapters. Chapter 1 introduces the motivation and the objectives of this research. It discusses the theoretical background required to understand electrodeformation phenomenon as well as the working principle of nanopore resistive pulse sensing. Chapter 2 discusses the electrodeformation of synthetic liposomes inside nanopores. Resistive pulse measurements of liposomes with varied composition and mechanical properties are compared and correlation between elasticity and resistive pulse characteristics is established. Chapter 3 is dedicated to characterizing the morphology of deformed liposomes inside nanopores. In this chapter, multiphysics simulations are used to establish a relationship between resistive pulse signals and shape characteristics of liposomes. Translocation events of particles with various shapes through a nanopore are modeled and the differential equations for the underlying physics are solved to simulate a resistive pulse signal. These simulated signal are then compared the experimental data from chapter 2 to predict the shape of deformed liposomes inside nanopores. Chapter 4 demonstrates the ability of our platform to compare elasticity of pseudotype human immunodeficiency viruses type 1 (HIV-1). The elasticity of immature and mature viruses is compared based on their respective resistive pulse signals. In addition, the effect of cholesterol on the mechanical properties of mature viruses is investigated by removing cholesterol from their membranes. Furthermore, a recapturing protocol is employed to investigate the elastic properties of a single virion as opposed to average ensemble measurements. Chapter 5 is dedicated to explaining current challenges and opportunities for future works. Important steps to follow this research are suggested and potential experimental or theoretical investigations to overcome current challenges are proposed. Opportunities for future research in both fundamental and applied sciences are further discussed. In conclusion, our findings lay the groundwork to develop novel enabling technologies based on nanopore resistive pulse sensing for characterization of vesicles' elastic properties at nanoscale. Our data suggests that such platform can offer significant advantages over current state-of-the-art systems particularly in terms of throughput, costs and operability.
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Details
- Title
- Electrodeformation in Solid-State Nanopores and its Application for Characterization of Nanoscale Vesicles and Viruses
- Creators
- Armin Darvish - DU
- Contributors
- MinJun Kim (Advisor) - Drexel University (1970-)Ming Xiao (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xx, 112, 2 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- School of Biomedical Engineering, Science, and Health Systems (1997-2026); Drexel University
- Other Identifier
- 7797; 991014632590304721