UC San Diego

Cancer is the second leading cause of death, claiming ̃0.56 million lives in the U.S. every year following heart diseases (̃0.62 million). From 1991 to 2007, mortality associated with heart diseases decreased 39%; by contrast, the death rate of cancer only decreased by 17% in spite of intensive research and improved therapeutics. The stagnation of conventional medicine and the complexity of cancer demand new therapeutic strategies. As an emerging approach, the use of nanomaterials as cancer diagnostic and therapeutic agents has shown promising results due to their unique physical and chemical properties. To date, more than two dozen nanoparticle-based products have been approved for clinical use and they show advantages over conventional therapeutics. However, translation of many other nanomaterials has been impeded due to concerns over toxicity and biodegradability. This dissertation presents the development of biodegradable luminescent porous silicon nanomaterials and their potential applications for imaging and treatment of cancer. Chapter 3 presents a diagnostic application of LPSiNPs. Time-gated fluorescence imaging of tumors using LPSiNPs with long emission lifetime is developed. This technique can effectively eliminate interference from short-lived tissue autofluorescence and improve the detection sensitivity. Chapter 4-6 demonstrate the therapeutic applications of porous silicon nanomaterials. In Chapter 4, magnetically- guided delivery of anticancer drug to cancer cells in vitro is achieved using magnetic, luminescent porous Si microparticles. Chapter 5 demonstrates that porous silicon nanoparticles can be used as photosensitizer and generate cytotoxic singlet oxygen when irradiated by light. The phototoxicity of the nanoparticles against cancer cells is also studied. Finally, the use of LPSiNPs for immune activation is investigated in Chapter 6