Polymeric nanoreactors were also used to perform ring-opening polymerization (ROP) in water. Nallani et al. reported on the enzymatic polymerization of lactones using CalB, which was immobilized in both the polymersome lumen and bi-layer . Nanoreactors for ROP were prepared from polystyrene-polyisocyanopeptide (PS-PIAT) and CalB was incorporated within either the lumen or polymer membrane (Figure 5).