  We demonstrated a biosensing approach which, for the first time, combines the
high-sensitivity of whispering gallery modes (WGM) with a metallic nanoparticle
based assay. We provided a computational model based on generalized Mie theory
to explain the higher sensitivity of protein detection through Plasmonic
enhancement. We quantitatively analyzed the binding of a model protein (i.e.,
BSA) to gold nanoparticles from high-Q WGM resonance frequency shifts, and fit
the results to an adsorption isotherm, which agrees with the theoretical
predictions of a two-component adsorption model.
