ABSTRACT OF THE THESISTitle By Alyssia Fossorier Master of Science in Biomedical Engineering University of California, Irvine, 2024 Professor Jered B. Haun, Chair

Cancer, particularly breast cancer, poses a significant global health challenge, affecting millions of women annually and remaining a leading cause of death. Early detection is crucial for improving outcomes, yet many cases go undiagnosed until advanced stages highlighting the need for accurate diagnostics. This thesis explores optical imaging and fluorescence lifetime imaging microscopy (FLIM) to enhance early detection in breast cancer.Two key aspects of fluorescence imaging are focused on: enhancing the stability of fluorescent dyes, specifically quantum dots, through silica coating, and analyzing fluorescence lifetime using the phasor approach. Silica coating improves the stability and biocompatibility of quantum dots by acting as a protective barrier preserving their optical properties and preventing aggregation. The phasor approach in FLIM is used to analyze the behavior of fluorescent dyes, revealing distinct fluorophore positions on the phasor plot and providing insights into fluorescence decay and self-quenching. Overall, the benefits of silica coating for dye stability and the insights gained through phasor plot analysis in FLIM can advance fluorescence imaging techniques. Future work should focus on applying these techniques to improve diagnostic accuracy in breast cancer analysis.