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Author ORCID Identifier

https://orcid.org/0000-0002-3312-1592

Document Type

Campus-Only Access for Five (5) Years

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Civil and Environmental Engineering

Year Degree Awarded

2019

Month Degree Awarded

September

First Advisor

Boris Lau

Subject Categories

Environmental Engineering | Nanomedicine

Abstract

Identifying the mechanisms of interactions of nanoparticles (NPs) with biological interfaces (e.g., the surface of cell membranes and proteins) is the key for enhancing the performance of NPs in various applications (e.g., as carriers for drug delivery) and minimizing unintended consequences (e.g., cytotoxicity). Nano-bio interactions are not only determined by the surface properties of NPs (e.g., charge, hydrophobicity and curvature) but also on the components of the immediate surrounding medium (e.g., solute type and concentration). Many reports in the literature point out that cationic NPs can induce more membrane disruption than anionic ones. In contrast, my results showed that anionic polystyrene NPs are also capable of binding and penetrating supported lipid bilayers (SLBs) formed by zwitterionic DOPC lipids when charge and hydrophobicity work in concert with specific anions. The preferential deposition of anionic NPs onto the bilayer is rationalized electrostatically by considering the slightly positive charge of DOPC. In addition to charge, NP hydrophobicity played an important role in the subsequent penetration of anionic NPs into SLBs. The extent of NP deposition was modulated by chaotropic anions (NO3−). vii To better mimic the fate of NPs in the physiological environment, I further investigated how zwitterionic osmolytes in combination with specific anions modulate NP-SLB interactions. I found that osmolytes are capable of protecting SLBs from being disrupted by NPs albeit to different extents depending on kosmotropic or chaotropic nature of osmolyte. The combination of kosmotropes (i.e., F− and trimethylamine N-oxide) are more effective than that of chaotropes (i.e., NO3− and urea) in weakening the hydrophobic NP-SLB interactions by preferential binding to NPs and/or SLBs. Rational optimization of NP surfaces is essential for successful conjugation of proteins to NPs for numerous applications. Using surface-roughened gold NPs (SRNPs) and quasi-spherical gold NPs (QSNPs) as two model nanostructures, I examined the effects of local surface curvature on bovine serum albumin (BSA) conformation and interfacial behaviors. My findings demonstrated that: 1) SRNPs possess higher tendency to denature BSA and accommodate a higher number of BSA molecules on the surface and 2) the aggregation of AuNP-BSA complexes, likely induced by either denatured BSA (for QSNPs) or reduced electrostatic repulsion between complexes (for SRNPs), is dependent on both the BSA concentration and the NP surface roughness.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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