Synthesis, functionalization, and bioconjugation of monodisperse, silica-coated gold nanoparticles: Robust bioprobes

Herein, we report an efficient process for preparing monodisperse Au@SiO2 nanoparticles using homogeneous shaking and without the use of surface-coupling silane agents or large stabilizers. The resulting pure-silica surface of the Au@SiO2 nanoparticles is very important for straightforward surface functionalization with different functional groups via well-established silica surface chemistry. Subsequent covalent bioconjugation of the aldehyde-functionalized Au@SiO2 nanoparticles with various biomolecules is successfully employed to make robust nanoprobes for fast, colorimetric DNA and protein detection based on the sequence-specific hybridization properties of DNA and the specific binding affinity between proteins, respectively.