Abstract: A method for detecting changes of magnetic response of at least one magnetic particle provided with a external layer in a carrier fluid, comprising measuring the characteristic rotation time of the magnetic particle with respect to the external layer, and measuring Brownian relaxation in the carrier fluid under the influence of an external alternating magnetic field. The method implies that upon modification of the effective volume of the particle or its interaction with the carrier fluid, a hydrodynamic volume of the particle changes, which implies a change of the frequency (ƒmax) at which an out of phase component of the magnetic susceptibility has its maximum.

Abstract: The present invention relates to a method for detecting changes of magnetic response of at least one magnetic particle provided with an external layer in a carrier fluid, wherein the method comprises using a measuring method comprising measuring the characteristic rotation time of said magnetic particle with respect to said external layer, which measuring method involves measuring Brownian relaxation in said carrier fluid under the influence of an external alternating magnetic field. The method implies that upon modification of the effective volume of the particle or its interaction with the carrier fluid a hydrodynamic volume of the particle changes, which implies a change of the frequency (fmax) where an out of phase component of the magnetic susceptibility has its maximum.