Superparamagnetic monodispersed particles

superparamagnetic, monodisperse, process for their preparation and their uses, these particles comprising: a core based on a first polymer, an internal layer covering the core, based on a second polymer and in which is distributed a magnetic material, and an outer layer covering the magnetic layer, based on a third polymer and capable of interacting with at least one biological molecule, at least the second polymer is heat-sensitive and having a lower critical solubility temperature (LCST) between 15 and 65 ~ C.