microscopy: a new way of seeing inside tissues and cells

Researchers have developed a powerful new method to peer inside cells and tissues. As reported in this week’s Proceedings of the National Academy of Sciences Early Edition, Stephan Thiberge of Israel’s Weizmann Institute of Science and his colleagues have come up with a way to use the scanning electron microscope, or SEM, on these “wet” biological specimens. Samples to be examined by SEMs, which use focused beams of electrons instead of light to scan the surface of objects, traditionally must be held in a high-vacuum environment. Under these conditions, a sample that holds water, such as a piece of tissue or a cell, is explosively unstable, so it has to be dehydrated, changing its normal appearance. To circumvent this problem, the researchers found a way to protect the fluid-filled sample from the vacuum by using a thin polymer membrane transparent to the electron beam. Using the “wet SEM” technique, the researchers were able to see not only the exterior of a cell, as in a traditional SEM, but its interior structures as well. The researchers believe their method opens opportunities for medical investigations, including tissue biopsies.

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 2/24/2004.