A suspension of vector particles (PV) based on polyamino acids and have a mean hydrodynamic diameter between 30 and 120 nm, and an insulin load factor of from 5 to 25% of associated insulin volume relative to the polyamino acid volume forming the vector particles. The polyamino acids are double-block polymers containing hydrophilic and hydrophobic monomers. The suspension may be prepared by copolymerizing N-carboxy anhydrides of hydrophobic monomers and precursors of hydrophilic monomers, in the presence of N-methyl pyrrolidone and methanol. The copolymer is optionally neutralized, subjected to dialysis, concentrated and water is eliminated to produce a solid powder, which can be suspended in a liquid to produce the colloidal suspension. Active principles such as insulin or vaccines are associated with the carrier particles to prepare special pharmaceutical products.