Ultra-bright Raman dots for multiplexed optical imaging

Imaging the spatial distribution of biomolecules is central to modern biology. Fluorescence techniques enable nanometer-precision subcellular imaging but multiplexing is limited by spectral crowding of fluorescent materials. Raman methods offer much higher spectral resolution but often lack sensitivity for biomarker imaging. Here we present Raman-active nanoparticles (Rdots) that are ultra-bright and compact (~20 nm). Using stimulated Raman scattering (SRS) microscopy, Rdots are 2–3 orders of magnitude brighter than prior Raman-active organic probes, with evidence supporting single-particle level SRS imaging. Their compactness and brightness enable immunostaining of specific protein targets (including cytoskeleton and low-abundance surface proteins) in cells and tissue slices with high contrast. Rdots provide a promising tool for studies of complex biological networks.