SEMINAR: CMCA Seminar Series

'Measuring nanoparticle dispersion and in vitro cellular uptake by electron microscopy' presented by Nicole Hondow from the Institute for Materials Research, University of Leeds

Engineered nanoparticles have been the focus of much recent research with a wide-range of potential applications in catalysis, biomedicine, magnetic resonance imaging, data storage and environmental remediation. For biomedical applications these particles often have surface modification with organic molecules to stabilise them in biological suspensions, functionalise the surface and avoid immediate uptake or clearance by the immune system. Understanding the structure of particles after modification and when within cellular environments is criticial to their safe and successful application. At Leeds we have been developing a systematic approach to the characterisation of nanoparticles and their cellular uptake using electron microscopy. One approach is to draw on the imaging and analytical capabilities of transmission electron microscopes (TEMs) to characterise these particles before and after cellular uptake. A key challenge for this work is representative sample preparation, and we are examining this using CdTe/ZnS core/shell quantum dots dispersed in biological media and serum. The uptake of these nanoparticles by U2-OS human osteosarcoma cells has been examined by quantitative TEM imaging to determine the distribution of the nanoparticles in membrane bound vesicles and the cytoplasm. This is being extended into 3-D, using the Gatan 3-View system in the scanning electron microscope (SEM) to serial section resin-embedded cells exposed to quantum dots. By combining the information from TEM imaging (i.e. location and number of vesicles per 2-D cell section plus the number of quantum dots per vesicle) and serial sectioning (i.e. location, size and number of vesicles in whole cells (3-D)) with that provided by other techniques (such as optical imaging,) we are developing a fully quantitative description of cellular uptake of these quantum dots.