A novel enzyme responsive amphiphilic copolymer was synthesized.The copolymer was composed of hydrophobic polylactide (PLA) and hydrophilic αmethoxy-poly(ethyl glycol) (MPEG) block.The two blocks were conjugated through 5

5′-azodisalylic acid (OLZ) (MPEG-OLZ-b-PLA).The chemical structure of the copolymer was verified by FTIR

NMR and GPC.The NMR characterization demonstrated that the copolymers could be synthesized by esterification and purified by precipitation and dialysis.The micellization behavior of the copolymer in aqueous media was studied with transmission electron microscopy (TEM) and dynamic light scattering (DLS).The results showed that MPEG-OLZ-b-PLA self-assembled into spherical micelles with diameter at about 30 nm.The critical micelle concentration (CMC) of the copolymer was 2.69×10-3 g/L.The enzyme-degradation experiment demonstrated that the MPEG-OLZ-b-PLA micelles could be specifically degraded in rat cecum contents.And the degradation curve had two time platform with no change in azo content.The first platform phase resulted from the induction period of the enzyme so that desirable concentration of the enzyme could be achieved for initialing the degradation of the copolymers.The second could be attributed to the slow dynamic process for azoreductase to migrate into the micelles.Such degradation behavior of the copolymers suggested of potential usefulness to colon-site specific delivery.