Opto-magnetophoretic method for the detection of biological and chemical substance

A method for detecting the presence or absence of a biological or chemical substance in a particular sample mixed with a suspension with functionalized magnetic particles, the particles having a diameter between 10 and 1000 nm and a saturation magnetization such that their magnetic separation time is different in the absence or presence of the biological or chemical substance, by monitoring the optical properties of the suspension, the method comprising the steps of:

• providing a light source and detector;
• providing a constant magnetic force perpendicular to the light's propagation direction by applying a constant magnetic field gradient, and with an absolute value of the magnetic field which is higher than 0.1 T;
• measuring the change of the magnetic particle's suspension transparency versus time;
• and
• comparing the variation along time of the magnetic particle's suspension transparency in the presence and in the absence of the biological or chemical substance of interest,
• wherein the magnetic force is provided by a magnetic force generator comprising at least four permanent magnets following the Halbach progression for a quadrupole in a cylindrical support.