We report on a nanoparticle-based biosensor that represents a label-free homogeneous bioassay suitable for in-vitro biomolecular diagnostics. The underlying detection principle is based on the optical observation of the rotational dynamics of multicomponent nanoparticles utilizing magnetic and plasmonic properties. The plasmon-optical properties of the anisotropic nanoparticles depending on their material composition and geometrical design were investigated by numerical simulations. Based on such an analysis, monodisperse magneto-plasmonic nanoparticles were fabricated using physical fabrication methods. Rotational dynamics measurements revealed the lowest detectable particle concentration in the picomolar (ng/mL) regime, which is very promising in reaching the biomolecular limit of detection which is relevant for routine clinical diagnostics.
