The invention concerns delivery particles (DP's) for active principles (AP's) based on linear amphiphilic polyamino-acids (PAA's), with &agr;-peptide chains, capable of being spontaneously formed by contacting PAA's with a liquid medium, preferably with water, wherein the hydrophile part of the PAA's is solubilized more than the hydrophobic parts of said PAA's, such that the latter precipitate while being organised in discrete supra-molecular arrangements, of average size ranging between 0.01 and 20 &mgr;m, capable of combining with at least an AP and releasing the latter in vivo, in prolonged and controlled manner. The inventive suspension is characterised in that the recurrent amino acids (rAA's) constituting the main chain of PAA's are identical to or different from one another and are glutamic acid and/or aspartic acid and/or their salts; and some of said rAA's bear at least one hydrophobic group, said hydrophobic group, being identical to or different from one another. The invention is useful as carriers for active principles, in particular pharmaceutical, insulin or for therapeutic uses.