| AVS 60th International Symposium and Exhibition | |
| Nanoparticle-Liquid Interfaces Focus Topic | Friday Sessions |
| Session NL+AS+BI+SA-FrM |
| Session: | Emerging Methods to Identify and Measure Nanomaterials in Biological Environments |
| Presenter: | X.M. Ma, Southern Illinois University Carbondale |
| Authors: | X.M. Ma, Southern Illinois University Carbondale J. Geisler-Lee, Southern Illinois University Carbondale M. Amati, Sincrotrone Trieste, Italy L. Gregoratti, Sincrotrone Trieste, Italy S. Guenther, Technical University Muenchen, Germany M. Kiskinova, Sincrotrone Trieste, Italy A. Kolmakov, Southern Illinois University Carbondale |
| Correspondent: | Click to Email |
The increased use of engineered nanoparticles (ENPs) in biomedical applications and their inevitable release into the environment has prompted considerable need to study of their uptake, accumulation and transport inside biological tissue and in plants. This is particularly true for addressing the ENPs fate on a cellular level which inevitably requires the microscopy approach. For long time optical microscopy with the resolution in the order of 100 nm was the major tool available. Better resolution can be readily achieved with traditional transmission (TEM) or scanning (SEM) electron microscopy. However, it requires histological sample treatments such as fixation, staining, dehydration, freezing etc which excludes in vivo (in situ) modes of observations and can alter their native morphology, functionality and living cycles. Different from standard environmental SEM, where the near sample pressure is limited by ca few tens of Torr, we are actively working on fabrication and tests of electron transparent membranes for ambient pressure electron spectromicroscopy and its application to fully hydrated samples for phytotoxicity, and materials research. Such enclosed environmental cells, equipped with 50-100 nm windows transparent for 10-20 keV electrons, can maintain the sample at atmospheric pressure and/or fully hydrated. This approach is beneficial compared with dry methods since in vivo SEM/TEM observations at nanoscale can be performed. Using this methodology, we were able to image the uptake of silver (Ag) NPs by living Arabidopsis roots on a cellular level. It was shown that NPs with the sizes larger than 20 nm accumulate preferably on the surface of the cellular walls and do not to traverse the plant cell membrane.
Recent developments in high yield fabrication and handling protocols of ultrathin (~1 nm) membranes, such as graphene or graphene oxide sheets with thicknesses comparable to the effective attenuation length (EAL) of 200-1000 eV electrons opened the opportunity to perform traditional XPS (X-ray Photoelectron Spectroscopy) and AES (Auger Electron Spectroscopy) at the interfaces between the membrane and fully hydrated samples. Using model water solutions and NPs, we report here on major design principles of such cells as well on first spectral demonstrations, advantages and limitations of this new technique.