Interactions of Semiconductor Nanoparticles with Environmentally Relevant Bacteria Model

Abstract

The growth in nanotechnology and the specific interest in the use of semiconductor nanoscale quantum dots have increased recently. The environmental and health concerns over the use of cadmium (Cd) in quantum dots has led to research towards design and synthesis of Cd-free quantum dots. With the growth and synthesis of these alternative quantum dots, research is ongoing to understand their environmental and biological interactions and implications. In this thesis, I have focused on comparison of the toxic effects of conventional CdSe and CdSe/ZnS quantum dots, and various alternative quantum dots such as silicon quantum dots and Zn-based QDs, which are emerging as a potentially benign alternative, using bacteria as a model organism. I have also focused on studying the toxicity and stability of another semiconductor nanoparticle group, copper zinc tin sulfide nanoparticles. This research assesses changes in cell viability, respiration pattern, and cell membrane integrity in the presence of the nanoparticles using colony counting, respirometry and membrane integrity assays, respectively. The association of the QDs with bacterial cell membranes was investigated using transmission electron microscopy (TEM). Mechanism of toxicity is assessed via ion dissolution studies and reactive oxygen species monitoring.