a1 Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305-4034, USA
a2 Molecular Imaging Program at Stanford, Department of Radiology, Stanford University, Stanford, CA 94305-5427, USA
a3 Department of Radiology, University of Cambridge, Cambridge CB2 2QQ, UK
a4 Department of Bio-engineering and Bio-X Program, Stanford University, Stanford, CA 94305-5427, USA
The use of nanoparticles for the diagnosis and treatment of cancer requires the complete characterization of their toxicity, including accurately locating them within biological tissues. Owing to their size, traditional light microscopy techniques are unable to resolve them. Transmission electron microscopy provides the necessary spatial resolution to image individual nanoparticles in tissue, but is severely limited by the very small analysis volume, usually on the order of tens of cubic microns. In this work, we developed a scanning transmission electron microscopy (STEM) approach to analyze large volumes of tissue for the presence of polyethylene glycol-coated Raman-active-silica-gold-nanoparticles (PEG-R-Si-Au-NPs). This approach utilizes the simultaneous bright and dark field imaging capabilities of STEM along with careful control of the image contrast settings to readily identify PEG-R-Si-Au-NPs in mouse liver tissue without the need for additional time-consuming analytical characterization. We utilized this technique to analyze 243,000 μm3 of mouse liver tissue for the presence of PEG-R-Si-Au-NPs. Nanoparticles injected into the mice intravenously via the tail vein accumulated in the liver, whereas those injected intrarectally did not, indicating that they remain in the colon and do not pass through the colon wall into the systemic circulation.
(Received January 22 2013)
(Accepted May 16 2013)