Luminescent silicon quantum dots as a base for multimodal nanoplatforms
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Since the first reports of their use in biological contexts, QDs have confirmed their potential in biomedical application. QDs can potentially replace organic dyes in most biological applications because of their superior optical properties and photostability. However, most of the quantum dots studied to date, such as CdSe/ZnS, CdS, CdTe and PbSe, incorporate toxic heavy metal components, which may limit their use for in vivo studies. Comparatively few studies have reported the application of silicon quantum dots (SiQDs) in biology and medicine. Compared to other semiconductor materials, silicon is abundant, economical and inherently non-toxic. Silicon nanoparticles can be made via various chemical and physical routes. Our group uses high-temperature decomposition of silane to prepare silicon nanocrystals with typical sizes of 5 to 7 nm in diameter. As described in previous publications, our group is able to obtain water-dispersable silicon nanoparticles that have size-dependent photoluminescence. In spite of that, there are several challenges that must be overcome to use SiQDs as multimodal probes. In the work reported in this thesis, we have used several methods to demonstrate the potential of SiQDs for biosensing and bioimaging applications, including silicon FRET, paramagnetic SiQDs as MRI contrast agents, and SiQDs conjugates for siRNA delivery.