Stimuli-triggered growth and removal of a bioreducible nanoshell on nanoparticles.

A new and easy method of stimuli-triggered growth and removal of a bioreducible nanoshell on nanoparticles is reported. The results show that pH or temperature could induce the aggregation of disulfide-contained branched polymers at the surface of nanoparticles; subsequently, the aggregated polymers could undergo intermolecular disulfide exchange to cross-link the aggregated polymers, forming a bioreducible polymer shell around nanoparticles. When these nanoparticles with a polymer shell are treated with glutathione (GSH) or d,l-dithiothreitol (DTT), the polymer shell could be easily removed from the nanoparticles. The potential application of this method is demonstrated by easily growing and removing a bioreducible shell from liposomes, and improvement of in vivo gene transfection activity of liposomes with a bioreducible PEG shell.