Sixteen millions of people are diabetics in the United States. Finding an oral way to deliver the insulin they need would improve the quality of their life. For this purpose biodegradable and biocompatible nanovesicles encapsulating some insulin have been synthesized. Those nanovesicles are made by self-assembly of a triblock copolymer poly(ethylene glycol)-b-poly(lactic acid)-b-poly (glutamic acid). The triblock copolymer has been prepared in several steps by multi-step anionic ring- opening polymerization. The first step consisted in the preparation of the diblock copolymer PEG-b-PLA. The second step was the synthesis of the poly (glutamic acid). The polybenzyl(glutamic acid) was obtained by ring opening polymerization of the N- Carboxyanhydride of the corresponding amino acid. Finally, the benzyl group was deprotected via protonolysis, to generate the homopolymer. This triblock was successfully obtained by coupling a diblock copolymer PEG-b-PLA and a homopolymer poly (glutamic acid). In the presence of an aqueous solution of insulin, the triblock copolymer self- assembles in nanovesicles containing a part of the free insulin.