Moreover, the capsules' ability to osmotically shrink was examined by exposing them to high salt concentrations. The capsules are semipermeable for small water-soluble compounds but are impermeable for encapsulated macromolecules and colloids. This feature was harnessed to make microreactor capsules for the decomposition of hydrogen peroxide by the encapsulated PtNPs. Furthermore, the capsules' outer surface could be stably and selectively functionalized with a PEG3000cholesterol linker, whereby the cholesterol was inserted into the hydrophobic domains of the APCN.