Binding a target substance

A process for separating a target substance from a sample containing the target substance, the process comprising:

• (a) providing magnetic beads in a liquid, wherein each magnetic bead includes a magnetic material coated with a matrix material, the matrix material having an affinity for the target substance and having a surface comprising hydrophilic functional groups which promote disaggregation of the magnetic beads in the liquid, the magnetic material including one or more magnetic particles comprising ferrimagnetic, metal oxide and having a length or diameter of about 100 nm to 300 nm, and wherein the magnetic beads form aggregates due to remanent magnetization in the absence of a magnetic field;
• (b) disrupting the aggregates by an external force to form a dispersion of the magnetic beads suspended in the liquid;
• (c) contacting the dispersion of the magnetic beads with the sample containing the target substance to allow the target substance to bind to the magnetic beads;
• and
• (d) extracting the magnetic beads bound to the target substance from the sample by applying a magnetic field to thereby separate the target substance from the sample.