Polarization microscopy with stellated gold nanoparticles for robust monitoring of molecular assemblies and single biomolecules.

Advances in plasmonic nanoparticle synthesis afford new opportunities for biosensing applications. Here, we apply a combination of a new type of plasmonic nanomaterial - stellated nanoparticles, and polarization-sensitive darkfield microscopy for detecting molecular assemblies and tracking of individual epidermal growth factor receptors within single live cells with high signal-to-background ratio. Depolarization of linear polarized light by stellated nanoparticles is over 15-fold more efficient than similarly-sized spheroidal nanoparticles. This efficient light depolarization allows robust detection of molecules labeled with stellated nanoparticles in cross-polarized imaging where the intrinsic light scattering from cells is significantly reduced. The imaging can be carried out with single molecule sensitivity for essentially unlimited time with no signal degradation.