Formation and degradation of layer-by-layer-assembled polyelectrolyte polyrotaxane capsules.

We report the preparation of degradable capsules via layer-by-layer assembly using polyelectrolyte (PE) polyrotaxanes (PRXs). The PRX capsules were prepared by the sequential deposition of PRXs onto silica particles followed by the dissolution of the silica cores. The colloidal stability of the PRX capsules that are formed depends on the salt/buffer solution used in the assembly process. Various salt/buffer combinations were examined to avoid aggregation of the core-shell particles during PRX assembly and core dissolution. Using appropriate assembly conditions, we prepared colloidally stable, robust capsules. PRX capsules consisting of eight layers of PE PRXs had a wall thickness of ~15 nm. The degradation of the PRX capsules was demonstrated through the disassembly of the PE PRXs using glutathione, which cleaves the disulfide bonds linking the end-capping groups of the PE PRXs. Given the supramolecular noncovalent structure of PRXs and their adjustable properties, it is expected that PRXs will be used as building blocks for assembling advanced capsules with unique and tailored properties.