Imaging whole cells in liquid

4th March 2013

Scientists have always wanted to take a closer look at biological systems and materials. From the magnifying glass to the electron microscope, they have developed ever-increasingly sophisticated imaging devices.

Niels de Jonge, Ph.D. - along with Dr. Diana B. Peckys (post-doc at the University of Tennessee in Knoxville and Materials Science and Technology Division, Oak Ridge National Laboratory) Dr. GertJan Kremers (post-doc molecular physiology and biophysics (Piston group), Vanderbilt University Medical School), and Prof. Dr. David W. Piston (molecular physiology and biophysics, Vanderbilt University Medical School - added a new tool to the biology-watcher's box. In the online early edition of the Proceedings of the National Academy of Sciences, they described a technique for imaging whole cells in liquid with a scanning transmission electron microscope (STEM).

Scientist Live spoke with Dr. de Jonge about his work.

What prompted you to undertake this project?

Interest to investigate the mechanisms underlying cellular function at the nanoscale. Now that the genome has been encoded the scientific challenge of the century is to figure out how all proteins work together inside the cell. I started the liquid STEM project with the goal to image labeled proteins in
whole cells in liquid with a resolution of a few nanometer, which is something that is very much needed to understand protein function, but which is not possible with existing techniques.

I was also inspired by the following two publications:
- Thiberge et al. (2004) PNAS 101, 3346.
- Williamson et al. (2003) Nature Materials 2, 532.

How did you approach the development of liquid STEM? Were there any other options that were on the table but probably would not have worked?

To develop liquid STEM I have developed silicon chips with silicon nitride windows together with the company Protochips Inc (NC), various prototypes were developed and tested. I have developed 4 different fluid holders, three of them inside ORNL and with university collaborations, the last one with the company Hummingbird Scientific (WA). To support the design I have also developed a model for the image formation and the resolution. All together this was 3 years of work from the design phase to the successful experiments.

Can you describe the various ways liquid STEM compares with normal STEM, in particular how it addresses short comings in the traditional technique?

A normal STEM gives extremely high resolution, but works only in vacuum, so no liquid. Some systems were developed to image specimen in liquid with SEM and with TEM. But, SEM does not give sufficient resolution inside a cell, as it is a surface technique. TEM works with high resolution only for very thin samples (< 500 nm), but not for whole cells, or thicker samples in materials science.

What is next for your laboratory?

Find collaborations with biologists, to work on biological and biomedical problems, develop metallic tags for labeling inside the cell, investigate live cell imaging, develop imaging of operating batteries.

  (Reporting by Marc Landas)





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