the present invention relates to magnetic beads suitable for , for example , isolation of proteins , cells , and viruses and also for diagnostic applications and cell cultivation . the magnetic beads are composite beads with an inner core of metal particles , which are coated with an inert synthetic polymer and these are then enclosed in a hydrophilic porous polymer , preferably agarose . this provides porous biocompatible beads without metal leakage . the beads may be used for cell cultivation or for chromatography . when the beads are used for chromatography the agarose layer is preferably provided with ligands having affinity for selected biomolecules .