Ultra-small (3.1 nm) multifunctional CdS:Mn/ZnS core-shell semiconductor quantum dots (Qdots), which possess fluorescent, radio-opacity, and paramagnetic properties, have been shown here. To demonstrate in vivo bioimaging capability, a rat was administered endovascularly with Qdots conjugated with a TAT peptide. The labeling efficacy of these Qdots was demonstrated on the basis of the histological analysis of the microtome sliced brain tissue, clearly showing that TAT-conjugated Qdots stained brain blood vessels.

Water-in-oil (w/o) microemulsion synthesis of 70 nm size monodisperse TAT (a cell penetrating peptide, CPP) conjugated, FITC (fluorescein isothiocyanate) doped silica nanoparticles (TAT-FSNPs) is reported; human lung adenocarcinoma (A549) cells (in vitro) and rat brain tissue (in vivo) were successfully labeled using TAT-FSNPs.

Fluorescent, radio‐opaque, and paramagnetic silica nanoparticles 100 ± 10 nm in size are developed by incorporating fluorescent tris(2,2′‐bipyridyl) dichlororuthenium(II) hexahydrate and paramagnetic gadolinium ions. The nanoparticles are radio‐opaque due to the presence of electron‐dense Ru and Gd atoms. It is estimated that each nanoparticle carries about 16 000 Gd3+ ions. The multimodality of the silica nanoparticles is shown by fluorescence (Figure, left) and X‐ray (right) imaging.