Publication Date

5-2024

Advisor(s) - Committee Chair

Ali Oguz Er, Lawrence Hill, Matthew Nee

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

With the ever-increasing threat of antibiotic resistant bacteria, alternative treatment methods have been developed including photodynamic therapy (PDT). Within the PDT process, photosensitizers are used to generate reactive oxygen species (ROS) and facilitate the cell termination process. This work lays the conceptual foundation for the functionalization of the photosensitizer methylene blue (MB) with gold nanoparticles (AuNPs) and INF-55 as a potential inhibitor of the AcrAB-TolC efflux pump to enhance the effectivity of the PDT process.

AuNPs were synthesized using pulsed laser ablation in an aqueous citrate solution. Both nanosecond and picosecond pulse durations, as well as both 532 nm and 1064 nm wavelengths at various powers and frequencies were tested to determine the effect of laser parameters on particle synthesis. The nanosecond, 532 nm, 2.0 W laser parameters were determined to produce the most viable AuNPs for application in PDT with an average Feret diameter of 7.46 ± 3.28 nm. After synthesis, the AuNPs were characterized using transmission electron microscopy imaging, UV-Visible spectroscopy, fluorescence spectroscopy, and Fourier transform infrared (FTIR) Spectroscopy.

After synthesis and characterization of the AuNPs, the ROS generated in solution was measured by monitoring the photobleaching of 9,10-Anthracenediyl-bis(methylene)dimalonic Acid (ABMDMA). Molecular docking calculations were conducted to determine the viability of INF-55 as a competitive inhibitor for the AcrB subunit. The most probable binding mode for INF-55 had a binding affinity of –9.1 kcal/mol while the most probable binding mode for MB had a binding affinity of –7.2 kcal/mol.

Additionally, AuNPs were used in combination with MB in-vitro on the Gram-negative bacteria Escherichia coli (E. coli) to determine the effect of AuNPs on cell termination. When AuNPs were used with MB, a 99.98 - 99.99 % decrease in the bacteria concentration was observed as compared to a 97.51 % decrease with MB alone.

Disciplines

Life Sciences | Medicine and Health Sciences | Physical Sciences and Mathematics

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