In Vivo Molecular Probing of Cellular Compartments with Gold Nanoparticles

Surface-enhanced Raman (SERS) signatures were measured from single living cells at different times after the uptake of gold nanoparticles. The spectra are indicative of chemical changes in the environment of the nanostructures over time. The increase of the SERS signal strength and parallel TEM studies indicate the formation of nanoaggregates providing optimum SERS enhancement for ultrasensitive probing inside the endosomal compartment. The results have implications for medical and biotechnology applications of SERS nanosensors in cells. Owing to their favorable physical and chemical properties, gold nanoparticles have been useful tools in biology for several decades. Their high electron density has made them popular labels in electron microscopy, and because their surface properties enable a great variety of functionalization procedures1 they can be used to target selected structures in biological samples.2-4 The latter advantage, along with the universal biocompatibility of their material, has contributed to the increasing interest in utilizing gold nanoparticles as vehicles for drug and gene delivery.5,6 In past years, a numbe