Abstract

Amphiphilic block copolymers are unique macro-molecules capable of self-assembling into bilayers analogous to naturally occurring lipid membranes. When combined with lipids, these copolymers form hybrid membranes with unique and sometimes unpredictable properties, including increased chemical and mechanical stability. These synthetically enhanced biological structures represent a versatile platform suitable for a wide range of applications, from advanced biosensing devices to drug delivery systems. The realization of these advancements necessitates a deep understanding of material properties, including the ability to predict and control interfacial behaviors. It has been shown that in the case of pure lipid membranes, interfacial behaviors are dominated by electrostatic forces. The following work will demonstrate that, electrostatic forces also represent a major driving force behind hybrid vesicle adhesion events, such as the formation of supported bilayers or interactions with biological tissues. These electrostatic forces can be manipulated to a limited degree by adjusting suspension buffer pH which primarily modulates the substrate zeta potential. Protonation of silanol groups, in the case of silicate surfaces at low pH, results in slightly positive surface zeta potential. Unfortunately, hybrid vesicles containing BdxEOy polymers exhibit a slight negative zeta potential independent of buffer pH conditions. Therefore, pH mediation can only result in supported bilayer formation in limited cases and may be insufficiently robust for many demands of application. Furthermore, the zeta potential of hybrid vesicles is surprisingly difficult to predict and control, likely due to screening and steric effects of the PEO block. This investigation provides a model to tune and control the zeta potential of such vesicles, independent of other tunable properties. This technique, in combination with pH mediation, proves to be especially effective in controlling vesicle-substrate interaction. Furthermore, translating this understanding to interactions with tissues, could facilitate more targeted drug delivery, potentially avoiding sensitive tissues, thus reducing off-target effects. In summary, this work deepens our understanding of the complex relationship between surface-potential, pH conditions, and vesicle behavior, paving the way for novel applications in bio-sensing, drug delivery, and nanotechnology.

Degree

PhD

College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2023-12-07

Document Type

Dissertation

Handle

http://hdl.lib.byu.edu/1877/etd13061

Keywords

amphiphilic block copolymers, polymers, polymersomes, hybrid vesicles, lipids, membranes, vesicles, soft matter, biosensing, biomedical applications, biomimetic, drug delivery

Language

english

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