Cellular uptake and nanoscale localization of gold nanoparticles in cancer using label-free confocal Raman microscopy

This work demonstrates the use of confocal Raman microscopy (CRM) to measure the dynamics of cellular uptake and localization of gold nanoparticles (GNP) with nanoscale resolution. This is important as nanoparticle cellular interactions are increasingly under investigation to support applications as diverse as drug delivery, gene transfection and a variety of heat and radiation based therapeutics. At the heart of these applications is a need to know the dynamics of nanoparticle cellular uptake and localization (i.e., cell membrane, cytoplasm or nucleus). This process can change dramatically based on size, charge, shape and ligand attached to the nanoparticle. While electron microscopy, atomic emission spectroscopy and histology can be used to assess cellular uptake, they are labor intensive and post-mortem and can miss critical dynamics of the process. For this reason investigators are increasingly turning to optically active nanoparticles that allow direct microscopic interrogation of uptake. Here we show that CRM adds to this evolving armamentarium as a fast, noninvasive, and label-free technique to dynamically study cellular uptake of GNPs with subcellular detail in cancer. Raman laser interaction with GNPs inside cells shows unique spectroscopic features corresponding to the intracellular localization of GNPs over 2 to 24 h at the membrane, cytoplasm or nucleus that are separately verified by histology (silver staining) and electron microscopy. These results show that CRM has the potential to facilitate high-throughput study of the dynamics and localization of a variety of GNPs in multiple cell types.