Magnetoplasmonic nanostructures for biological applications
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Plasmonic nanostructures have received great attention from the nanoscience community due to their unique tunable optical properties, especially the colloidal gold nanorods. An intense NIR absorption of gold nanorods, created by longitudinal surface plasmon resonance, provides opportunity for outstanding optical imaging and therapeutic modalities in deep tissue due to their tunability to the "transmission window" for biological tissues in the range of ∼650 to 900 nm. The engineering of biocompatible gold nanorods has grown very rapidly because the designed nanoformulation is beneficial for many biological applications such as gene delivery, bio-imaging, photothermal therapy, and biosensors. The work reported in this dissertation focuses on the biomedical imaging and imaging-guided therapy applications, specifically photodynamic and photothermal therapy with gold nanostructures. The use of a low toxicity polyethyleneglycol coated (PEGylated) gold nanorod formulation for tumor imaging, based on passive targeting, has confirmed that the functionalized gold nanorods can serve as biocompatible colored probes for replacing heavy metal-based nanoparticles in biomedical applications. This finding will provide a basis for guided optical surgery to remove the cancerous areas, without harming the normal tissues. In addition, our engineered nanoformulation is capable of being an incorporated probe for multiple imaging modalities such as optical imaging, magnetic resonance imaging (MRI) and Surface Enhanced Raman Scattering (SERS). The multimodal system is highly promising for the early diagnosis and therapy of cancer. The plasmonic nanostructures are also helpful in imaging-guided photodynamic therapy, for example, the presence of metal nanoshells provides photostabilization of encapsulated dye. In addition, plasmonic nanostructures can be employed for plasmonic photothermal therapy (PPTT) of cancer. Cancer cells in vicinity of the plasmonic nanostructures, heated by laser irradiation, undergo hyperthermia and death, resulting in drug-free tumor remission. Therefore, we propose here a promising magnetoplasmonic nanoplatform for enhanced photothermal therapy. It involves a combination of the gold nanorods and iron oxide nanoparticles within phospholipid nanomicelles. This formulation also demonstrates here the capability of magnetic-field controllable photoacoustic signal enhancement. Our preliminary data, presented in this dissertation is of value for developing a hybrid nanoplatform for deep tissue imaging and photoinduced therapy. Moreover, we introduce computer modeling to guide and interpret the experimental work, and also provide a fundamental understanding of underlying phenomena of photothermal generation.