Objective To prepare insulin- loaded polymeric nanoparticles based on polyethyleneimine- polycaprolactonepolyethylene glycol- polycaprolactone- polyethyleneimine pentablock copolymers and evaluate its in vitro release of insulin.Methods Polycaprolactone-polyethylene glycol-polycaprolactone(PCL-PEG-PCL) triblock copolymer was synthesized by ringopening polymerization method, and the pentablock copolymer was prepared by Michael addition reaction. The copolymers obtained were characterized by Fourier- transfor...