ABSTRACT
Silicon (Si) is the second most abundant element in the earth’s crust preceded only by oxygen, making Si the most abundant metallic element. For non-porous silica nanoparticles, molecular dyes can be incorporated into the silica matrix itself, or in the interior forming a dye-rich core that finally is encapsulated into a solid silica shell; or the dyes can be introduced via a layer-by-layer technique where dye-rich layers are sandwiched between layers of solid silica. Nanoparticles have been widely used as labels in diagnostic and imaging applications as they possess high specific activity, and even single binding events can be observed due to the extremely intense, e.g., photoluminescence signal of the particles as compared to molecular labels. The greatest benefit of the nanoscopic imaging, diagnostic or theranostic agents will most likely be the information that can be gained through imaging for promoting the development of new nanotherapeutic systems.
