Multifunctional silica nanoparticles with potentials of imaging and gene delivery.

This article reports the method of preparation of gadolinium oxide-doped silica nanoparticles (NPs) whose surface has been functionalized to anchor DNA onto it. The silica NP's surface was modified by 3-aminopropyltrimethoxysilane for DNA to bind electrostatically. Silica NPs with low polydispersity and encapsulating gadolinium oxide were prepared in the aqueous core of the reverse micelles. The average size of these spherical silica NPs doped with gadolinium oxide and dispersed in water is ∼ 50 nm as measured by dynamic light scattering and transmission electron microscopy. The plasmid DNA electrostatically held over NP's surface was firmly immobilized and protected from DNase attack. The gadolinium oxide-doped silica NPs are paramagnetic as observed from the nuclear magnetic resonance (NMR) line-broadening effect on proton spectrum of the surrounding water. In vitro transfection efficiencies of these gadolinium oxide-doped and DNA-conjugated silica NPs in COS-7 and 293T cells were found to be about 75% and 77% respectively of that of 'Polyfect®' as positive control. FROM THE CLINICAL EDITOR: This article reports the method of preparation of gadolinium oxide-doped silica nanoparticles (NPs) whose surface has been functionalized to anchor DNA. These NPs are paramagnetic with in vitro transfection efficiencies in COS-7 and 293T cells of about 75% and 77% compared to 'Polyfect®' as positive control.