Date of Award

Fall 2023

Document Type

Open Access Dissertation


Environmental Health Sciences

First Advisor

Jamie Lead


Nanoparticles (NPs), materials with dimensions ranging from 1 to 100 nanometers, are widely used in various consumer products, with silver nanoparticles (AgNPs) being the most prominent. Exposure to AgNPs occurs through multiple sources, including food packaging, supplements, and disinfectants, owing to their antimicrobial properties. Prior research has identified adverse health effects, such as cytotoxicity, toxicity, and Ag bioaccumulation resulting from AgNP exposure to bacteria in biological systems and the environment. However, most studies employ pristine, highly concentrated NPs, which may not accurately represent realistic exposure scenarios at environmentally relevant concentrations. This project investigates the fate and internalization of AgNPs, found in a commercially available consumer product, upon exposure to Escherichia coli (E. coli) strain MG1655 within simulated human gastrointestinal fluids (SGF). A multimethod approach is employed to: 1) Detect and characterize physico-chemical transformations of AgNPs, both before and after dynamic changes, with a focus on size, agglomeration, surface changes, and dissolution. 2) Determine optimal experimental conditions for exposure to the product (XAg) to prevent cellular lysis of commensal E. coli strain MG1655 cells in vitro. 3) Quantify the uptake of commercially available AgNPs by commensal E. coli MG1655 following oral ingestion of XAg in SGF, distinguishing between the internalized, sorbed, and suspended fractions; using 5 mM EDTA for periplasm removal and single-cell inductively coupled plasma mass spectrometry (SC-ICP-MS) for analysis. The results demonstrate that SGF has a significant impact on the dissolution behavior of commercially available AgNPs, leading to alterations in particle shape, size, and distribution. Notably, the minimum inhibitory concentration of XAg intended for consumer use (20 ppm) hindered the growth of E. coli MG1655 at concentrations exceeding 5 ppm, while the optimal concentration with no adverse effects on cell density was 1 ppb. Furthermore, SGF, despite inhibiting E. coli MG1655 growth, proved to be a suitable medium for mature cells harvested from the late log phase. This study ultimately quantifies Ag uptake by E. coli MG1655, revealing that 0.03% of Ag was internalized, 4.4% were in suspension, and 95.6% were sorbed or weakly bound to the periplasm. These findings offer invaluable insights into the behavior of AgNPs in environmentally relevant conditions within the human gastrointestinal system.


© 2024, Samantha McNeal Case

Available for download on Wednesday, December 31, 2025