UC Irvine

Breast cancer is the most diagnosed cancer in the world and is responsible for millions of deaths. Early-stage diagnosis enhances survival rates and extends life expectancy by enabling timely treatment interventions. Many cancer cell detection techniques have been developed, but lacking abundant probes limited their further application. The utilization of fluorescence lifetime and phaser plot approach makes it possible to push the limits. The fact that lifetime information exhibits in a semi phasor pixel by pixel makes detection easier and more convenient. However, developing suitable fluorescent probes for multiplexing is still challenging. Synthesizing new fluorescent species is time-consuming; additionally, it is hard to maintain a stable lifetime in a complex microenvironment. More importantly, the number of probes strongly restricted the application of the technique. Multiplexing with 4-6 probes has been demonstrated, but the probe capacity needs to be further expanded. Therefore, fluorescent lifetime nanoprobes based on silica shells were proposed. Silica is biocompatible and surface modification versatile. Fluorescent species or their mixtures were wrapped within 30-50 nm silica particles. Because dye molecules inside the silica shells were so close to each other, the quenching effect could be utilized to change the lifetime of nanoprobes. In this study, I developed fluorescence lifetime libraries based on novel nanoprobes in silica shells for breast cancer cells detection. First, a method was shown to prepare silica particles modified with Polyethylene Glycol (PEG), where cell staining tests proved that the particles could specifically bind to cancer cells. Secondly, the fluorescence lifetime libraries were built with different fluorescent species. Through two approaches, addition of dark quencher and self-quenching, the lifetime of silica probes was altered, and the limit on number of probes was expanded. Lastly, a tumor panel was built and individual probe was validated on cancer cells, which proved the feasibility of using the silica probe for multiplexing. In summary, this study demonstrated that the fluorescence lifetime libraries using the innovative silica nano probes would serve as a powerful tool for multiplexing in breast cancer cells detection.