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Author ORCID Identifier

https://orcid.org/0000-0003-4723-7569

AccessType

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Physics

Year Degree Awarded

2020

Month Degree Awarded

September

First Advisor

Anthony Dinsmore

Subject Categories

Biological and Chemical Physics | Biomaterials | Biophysics | Biotechnology | Statistical, Nonlinear, and Soft Matter Physics

Abstract

In this thesis we explore two experimental systems probing the interactions of nanoparticles with lipid bilayer membranes. Inspired by the ability of cell membranes to alter their shape in response to bound particles, we report two experimental studies: one of nanospheres the other of long, slender nano-rods binding to lipid bilayer vesicles and altering the membrane shape. Our work illuminates the role of particle geometry, particle concentration, adhesion strength and membrane tension in how membrane morphology is determined. We combine giant unilamellar vesicles with oppositely charged nanoparticles, carefully tuning adhesion strength, membrane tension and particle concentration.

In the case of nanospheres we show that spherical nanoparticles binding to lipid-bilayer membrane vesicles results in a remarkably rich set of collective morphologies that are controllable via the particle binding energy. We separately study cationic and anionic particles, where the adhesion is tuned by addition of oppositely charged lipids to the vesicles. When the binding energy is weak relative to a characteristic membrane-bending energy, vesicles adhere to one another and form a soft solid gel, a novel and useful platform for controlled release. With larger binding energy, a transition from partial to complete wrapping of the nanoparticles causes a remarkable vesicle destruction process culminating in rupture, nanoparticle-membrane tubules, and an apparent inversion of the vesicles.

In the case of nanorods when we increased adhesion strength, the primary behaviors observed are membrane deformation, vesicle-vesicle adhesion, and vesicle rupture. These behaviors are observed in well-defined regions in the parameter space with sharp transitions between them. We observed deformation of the membrane resulting in tubulation, texted surfaces, small dark aggregates, and large aggregates. These responses are robust and repeatable providing a physical understanding of the dependence on shape, binding affinity, and particle concentration in membrane remodeling. These findings help unify the diverse phenomena observed previously as well as present new particle induced morphologies. They open the door to a new class of vesicle-based, closed-cell gels that are more than 99% water and can encapsulate and release on demand, and show how to drive intentional membrane remodeling for shape-responsive systems.

DOI

https://doi.org/10.7275/van1-3v04

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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