Using intracellular plasmonics to characterize nanomorphology in human cells

Determining the characteristics and localization of nanoparticles inside cells is crucial for nanomedicine design for cancer therapy. Hyperspectral imaging is a fast, straightforward, reliable, and accurate method to study the interactions of nanoparticles and intracellular components. With a hyperspectral image, we could collect spectral information consisting of thousands of pixels in a short time. Using hyperspectral images, in this work, we developed a label-free technique to detect nanoparticles in different regions of the cell. This technique is based on plasmonic shifts taking place during the interaction of nanoparticles with the surrounding medium. The unique optical properties of gold nanoparticles, localized surface plasmon resonance bands, are influenced by their microenvironment. The LSPR properties of nanoparticles, hence, could provide information on regions in which nanoparticles are distributed. To examine the potential of this technique for intracellular detection, we used three different types of gold nanoparticles: nanospheres, nanostars and Swarna Bhasma (SB), an Indian Ayurvedic/Sidha medicine, in A549 (human non-small cell lung cancer) and HepG2 (human hepatocellular carcinoma) cells. All three types of particles exhibited broader and longer bands once they were inside cells; however, their plasmonic shifts could change depending on the size and morphology of particles. This technique, along with dark-field images, revealed the uniform distribution of nanospheres in cells and could provide more accurate information on their intracellular microenvironment compared to the other particles. The region-dependent optical responses of nanoparticles in cells highlight the potential application of this technique for subcellular diagnosis when particles with proper size and morphology are chosen to reflect the microenvironment effects properly. A finer way to look inside cellsResearchers in Canada have demonstrated a technique to gather high-resolution information about nanoparticles distributed within cells. The team, led by Muthukumaran Packirisamy of Concordia University, used hyperspectral imaging combined with dark-field imaging to detect nanoparticles injected into human cancer cells. The technique is quick and does not require that the nanoparticles be labeled. Interactions between the nanoparticles and their microenvironment affect the optical responses of the nanoparticles, making it possible to use them to detect differences between subcellular regions or compartments. The team tested the approach with three types of gold nanoparticles: nanospheres, nanostars, and an Ayurvedic medicine known as Swarna Bhasma. They found that nanospheres performed better than nanostars or Swarna Bhasma. By selecting particles of the appropriate size and morphology, this imaging technique can be a powerful tool for subcellular diagnosis.