Polarization microscopy with stellated gold nanoparticles for robust, in-situ monitoring of 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. (c) 2008 Optical Society of America.