The fabrication of self-assembled vesicles comprised entirely of an amphiphilic diblock copolymer of poly(ethylene oxide) (PEO) and polycaprolactone (PCL) was discussed. It was observed that in vivo drug release from these bioresobable polymersomes depend on both PCL matrix erosion and a drug's intrinsic permeability from the aqueous core through a membrane. It was found that the large membrane core thickness affords the opportunity for facile incorporation of both hydrophobic and hydrophilic compounds within a single complex delivery vehicle. The results show that the self-assembled vesicular structure architecture allows for the economic generation of mesoscopic colloidal devices.