Giving a general view of the colloidal stability of nanoparticles in a biological environment remains difficult. This comes mainly from the complexity of biological environments and the diversity of nanoparticles in terms of size distribution, shape, nature of external surface and nanostructure. In particular, the number of physico-chemical studies on “soft” organic particles obtained by self-assembly of bioconjugates remains low. To understand how the physico-chemical characteristics of "soft" nanoparticles direct their interactions with blood proteins, we propose, in collaboration with the Institut Galien, to study a concrete case where the nanostructure and the surface charge of the nanoparticles give different pharmacologically efficiency (analgesic). The objective is to study in detail how nanoparticles formed by self-assembly of bioconjugates interact with a model biological medium, taking into account both the main components (albumin, hemoglobin and lipoproteins) and the hydrodynamic flow from the circulation blood.