A seeded watermelon-like mesoporous nanostructure (mSiO(2)@CdTe@SiO2, mSQS) composed of a novel dendritic mesoporous silica core, fluorescent CdTe quantum dots (QDs), and a protective solid silica shell is successfully fabricated by loading QDs into dendritic mesoporous silica nanoparticles through electrostatic interaction, and then coating with a solid silica shell by the modified Stober method. The shell thickness of mSQS can be tuned from 0 to 32 nm as desired by controlling the reaction parameters, including the amount of silica precursor, tetraethyl orthosilicate, that is introduced, the solvent ratio (H2O: ethanol), and the amount of catalyst (NH3 center dot H2O). These fluorescent mSiO(2)@QDs@SiO2 nanoparticles possess excellent stability and thickness-dependent cytotoxicity, and are successfully applied to bioimaging.