Porous silica can form stable and biocompatible nanometer-sized hollow spheres, or vesicles, that are suitable for transporting and delivering drugs to their targets in the body. The clinical use of silica vesicles, however, has been obstructed by the tendency for the spheres to clump into aggregates in water-based solutions. A team led by Ye Liu from the A*STAR Institute of Materials Research and Engineering in Singapore has now circumvented this problem by attaching water-soluble, brush-shaped polymers called polyethylene glycol (PEG) to the shells of the silica vesicles1.
The researchers prepared nanometer-sized silica spheres from a precursor known as TEOS using polystyrene beads as templates. Then, after removing the templates by heating, they modified the outer surface of the spheres with nitrogen-containing organic linkers that reacted easily with the PEG polymers to produce polymer-functionalized vesicles.
In addition to dispersing well in solution, the newly synthesized vesicles maintained their small size even in highly diluted aqueous solutions. They also remained intact for over a year, highlighting their long shelf-life and stability.
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