The present disclosure relates to a process for the preparation of core-shell particles by the coacervation method encapsulating contrast agents for multimodal imaging. The process consists in: a.Providing a water in oil emulsion of a biocompatible polyelectrolyte polymer. b.Providing an aqueous solution of a biocompatible polyelectrolyte polymer having opposite charges of the polyelectrolyte of step a). c.Adding a crosslinking agent to the primary emulsion and the secondary solution. d.Adding at least a tracer independently to the primary emulsion or the secondary solution or emulsion. e.Adding the secondary aqueous solution to the primary emulsions and occurring of the complex coacervation leading to the separation of the coacervate particles. f.Optionally absorb a further tracer into the nanoparticles The disclosure also relates to the coacervates obtained by the above described process and their use as probe for multimodal imaging in the diagnostic field.
