The present invention relates to novel materials based ON biodegradable polyamino acids that are useful especially for the vectorization of active principle (s) (AP). The invention further relates to novel pharmaceutical, cosmetic and dietetic or phytosanitary compositions based ON these polyamino acids. The object of the invention is to provide a novel polymer starting material that is capable of being used for the vectorization of AP and makes it possible ON the one hand to achieve high polymer/AP ratios, and ON the other hand optimally to satisfy all the specifications required in the case in point: biocompatibility, biodegradability, ability to associate easily with numerous active principles or to solubilize them and ability to release these active principles in vivo. This object is achieved by the present invention, which relates first and foremost to linear polyamino acids comprising aspartic units or glutamic units and having hydrophobic grafts comprising hydrophobic groups containing from 8 to 30 carbon atoms and at least one of these hydrophobic grafts having at least one anionic charge and/or one or more mutually identical or different ionizable groups each capable of giving rise to at least one anionic charge. These polymers are amphiphilic and anionic and are capable of being converted easily and economically to particles for the vectorization of active principles and these particles themselves being capable of forming stable aqueous colloidal suspensions.
