The invention relates to novel biodegradable polyamino acid based materials which can be used for the vectorization of (an) active substance(s) (PA). The invention also relates to novel pharmaceutical, cosmetic, dietary or phytosanitary compositions based on said polyamino acids. The present invention which primarily relates to polyamino acids comprising aspartic units and/or glutamic unites some of which bearing at least one graft, characterized in that at least one of said grafts is joined to an aspartic or glutamic unite by means of an amide bond and in that at least one of said grafts comprises at least one oligoamino acid which is Leu, and/or Ileu, and/or Val, and/or Phe based. Said amide function ensure better stability with respect to hydrolysis than similar products of prior art. Advantageously, said polymers can be easily and economically transformed into active substance vectorization particles, said particles being able to form stable aqueous colloidal suspensions.
