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The scanning electron microscope (SEM) has been a basic research tool for fifty years, and for those fifty years, scientists have been looking for better ways to observe biological samples under its beam.
The problem is that the viewing chamber of the SEM must contain a vacuum (in which liquid water in tissues “boils” away). To overcome this difficulty, scientists have had to resort to all sorts of complicated procedures, including coating the specimens with an ultra-fine layer of gold, quick-freezing samples in special deep-freezes, or treating them with drying solvents.
Now, scientists at the Weizmann Institute of Science have found a way to view samples of biological materials in their natural, “wet” state. Their secret lies in the production of a very thin but tough polymer capsule to enclose the sample, allowing it to withstand the force of the vacuum. Says Dr. Ory Zik, who worked on the capsule with Professor Elisha Moses of the Physics of Complex Systems Department: “The material for the capsule is a result of advances in the area of semiconductors. We came across it while researching ways to apply automation techniques used in the semiconductor industry to the life sciences’ scanning electron microscopes.”
The capsule’s polymer is unique in that it is allows the electrons with which a SEM works to pass through unobstructed, giving scientists a clear view of what lies within, without the use of tricky, tissue-distorting procedures. Researchers hope the new method will advance the studies of biological materials, such as the lipids that make up fat, which are easily destroyed by the old sample preparation methods.
Since the discovery was made, Zik, in cooperation with Yeda, the business arm of the Weizmann Institute, has founded a company, called QuantomiX, based on this technology. The findings of the team were published in the March 9 Proceedings of the National Academy of Sciences, USA (PNAS).
Prof. Elisha Moses's research is supported by the Clore Center for Biological Physics and the Rosa and Emilio Segre Research Award.