Superparamagnetic monodispersed particles

PCT No. PCT/FR97/00912 Sec. 371 Date Jan. 15, 1998 Sec. 102(e) Date Jan. 15, 1998 PCT Filed May 23, 1997 PCT Pub. No. WO97/45202 PCT Pub. Date Dec. 4, 1997The superparamagnetic monodispersed particles comprise a core of a first polymer, an internal layer of a second polymer coating the core and in which a magnetic material is distributed, and an external layer of a third polymer coating the magnetic layer and capable of interacting with at least one biological molecule. At least the second polymer is heat sensitive and has a predetermined lower critical solubility temperature (LCST) of 15-65 DEG C. These particles may be used to isolate at least one biological molecule from a liquid specimen.