|Views through the ESEM: a flower (top) and pollen (bottom)|
Ask any of the students who took Fundamentals of Biological Electron Microscopy what they liked best about the Intersession course, and you get the same answer: the Environmental Scanning Electron Microscope (ESEM).
The $200,000 microscope was acquired last May through an undergraduate Howard Hughes Medical Institute grant. Used by researchers in biology, chemistry, and engineering, it is one of the centerpieces of the newly renovated Integrated Imaging Center, which opened last August on the first floor of Dunning Hall.
Though students in the course also learned to use transmission electron microscopes and related instruments, the ESEM quickly became the focal point for most of them, according to J. Michael McCaffery, Integrated Imaging Center director and an associate research professor in the Department of Biology.
“To be candid, the students just went bonkers over the ESEM, and for good reason,” says McCaffery, who sounds like the proverbial kid in a candy shop when he talks about this piece of equipment. “They loved it essentially because it is so easy to use and because it provides instant gratification and success in observing common, everyday things—moldy cheese or bread, their own hair, pond water—at thousands of times in magnification.”
Electron microscopes use beams of highly energetic electrons to produce images of objects at a much higher magnification than is possible with ordinary light microscopes. However, many electron microscopes (such as conventional scanning electron microscopes) don’t allow researchers to examine specimens that are wet or moist, which rules out many biological samples, as well as liquids, gels, foods, adhesives, grease, and others. The ESEM, on the other hand, lets one look at almost anything at a magnification of up to 100,000.
“Generally speaking, preparing samples for conventional SEMs is a very time-consuming, stringent process that includes fixing, dehydrating, drying, and subsequent metal coating to render the specimen ready,” McCaffery explains. “With the ESEM, you can literally look at fully hydrated, wet samples. In fact, in many cases, you can observe and image actual live specimens.”
Just ask sophomore Tuyen Nguyen, who says she became “enthralled” with the ESEM as she used it to image a variety of biological specimens. “I used it to look at pretty much anything from yeast to fungi to bumble bees,” says Nguyen, who took the Intersession course to prepare her for future work in cell and tissue engineering.
“I was fascinated and spent many idle hours playing with all of its knobs and settings. It’s a really cool microscope to learn about microscopy on. Usage of the ESEM was not hard to pick up; there is a straightforward set of protocols to follow, and for the most part an accompanying software program prompts you with basic instructions that you need to start up the microscope,” she says.
Students, however, are not the ESEM’s only fans. Oncology researcher Bert Vogelstein of the School of Medicine has used the scope to evaluate and characterize endospores from anaerobic bacteria as part of his research into treating colorectal tumors, and engineering professor Jennifer Elisseeff of the Whiting School finds it invaluable in her evaluation of collagen films to be used in tissue engineering projects, according to McCaffery.
“It’s wonderful,” he says, “that even though the Integrated Imaging Center is a facility of the Department of Biology, the equipment and personnel here have really become a microscopy resource, not only for researchers across Johns Hopkins, but also for researchers from other institutions around the country and across the world.”
"...even though the Integrated Imaging Center is a facility of the Department of Biology, the equipment and personnel here have really become a microscopy resource, not only for researchers across Johns Hopkins, but also for researchers from other institutions around the country and across the world.”
— J. Michael McCaffery