Epi-illumination through the microscope objective applied to darkfield imaging and microspectroscopy of nanoparticle interaction with cells in culture.

Existing darkfield illumination schemes are incompatible with many types of samples and/or procedures. We present a darkfield epi-illumination scheme which addresses these incompatibilities by providing illumination through the imaging objective. We validate the system performance using silver nanospheres in varying refractive index environments, characterize the intensity distribution of the darkfield illumination, and demonstrate system capabilities through a preliminary study of functionalized gold nanosphere interactions with cancer cells in culture. We observe a broadened scattering spectrum from unconjugated nanoparticles, as compared with anti-EGFR conjugated nanoparticles, upon incubation with cancer cells, and discuss the implications of this observation.