Magnetic nano or micro spheres can be separated easily and quickly by magnetic forces and will be used together with
bioaffine ligands e.g. antibodies or proteins with a high affinity to the target. The targets can be cells, bacteria or DNA / RNA.
Magnetic separation techniques are fast with simple handling of a sample vial and dealing with large sample volumes without
the need for time-consuming centrifugation steps.
handling of a sample vial and dealing with large sample volumes without the need for time-consuming centrifugation steps.
This also makes biomagnetic separation ideal for automated assay / analysis systems which will play a very important role in
the near future.

Magnetic particles for bioseparation consist of one or more magnetic cores with a coating matrix of polymers, silica or hydroxylapatite with terminal functionalized groups. The magnetic core generally consists either of magnetite (Fe O ) or maghemite (gamma Fe O ) with superparamagnetic or 3 4 2 3 ferromagnetic properties. Super paramagnetism is when the dipole moment of a single domain particle fluctuates rapidly in the core due to the thermal excitation so that there is no magnetic moment for macrosconic time scales. Thus the particles are non magnetic when an external magnetic field is applied but do develop a mean magnetic moment in an external magnetic field.

In contrast Ferromagnetic means that the particles have a permanent mean magnetic moment. Here the larger effective
anisotropy suppresses the thermally activated motion of the core moments.

Advantages of superparamagnetic particles are easy resuspension, large surface area, slow sedimentation and uniform distribution of particles in the suspension media. Once magnetized, the particles behaves as small permanent magnets, and thus form aggregates or lattice due to magnetic interaction. Advantages of ferromagnetic particles are very strong magnetic properties and therefore the fast separation with an external magnetic field even in viscous media. Ferromagnetic particles are recommended for the separation of DNA/RNA (Magnatosilica-DNA), whereas superparamagnetic particles are more suitable for all other applications.