Patent ID: 7332353

Claim:
A method for detecting or quantifying at least one analyte in a liquid medium, said method comprising: providing magnetic colloidal particles functionalized at the surface with at least one ligand specific for an analyte to be detected or assayed; pretreating the medium to be analyzed beforehand in order to make the analyte being sought reactive with respect to at least two molecules of one of its specific ligands, wherein the pretreatment comprises functionalizing the analyte with one of the partners of a high affinity binding couple; bringing said particles into contact with said medium to be analyzed; applying a continuous magnetic field to said medium, at a strength sufficient to cause said magnetic particles to be structured in the form of chains; maintaining said continuous magnetic field for a period of time sufficient to enable coupling or combination of at least one of the analytes concerned with at least two specific ligands present respectively on two consecutive neighboring particles of a chain; removing the magnetic field after the period of time sufficient to enable coupling or combination of at least one of the analytes; and determining the presence or absence of at least one of the analytes after removing the magnetic field and, where appropriate, a respective concentration of at least one analyte by the presence or absence of permanent chain(s) of magnetic colloidal particles.