Topics Covered
Understanding Function of Cells and Tissues
Accurately
Obtaining Microscopic Images of Biological Samples
maging Biological Samples Using The ORION PLUS Helium Ion Microscope
The ORION PLUS Capabilitites
Application
Understanding Function of Cells and Tissues
A key to understanding the function of cells and tissues is the ability to
image their structure. The way that musculoskeletal tissues are structured, for
example, will determine their ability to perform their mechanical functions. In
cellular material, the cell membrane mediates the exchange of material with its
environment, helping to drive biological responses.
Accurately Obtaining Microscopic Images of Biological
Samples
Many biological specimens, however, present obstacles to accurate microscopic
imaging. Many of these materials are non-conducting, making for a challenge in
obtaining a stable, high resolution image. Their organic composition also make
them susceptible to shrinkage under the influence of charged particle beams.
Thus it is desirable to create minimum impact to these sensitive structures in
order to image them successfully.
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Imaging Biological Samples Using The ORION PLUS Helium Ion Microscope
We can take advantage of the unique beam-sample interaction of a primary
helium ion beam in order to get past the challenges described above. For samples
that charge it is often possible to simply image at lower beam current in order
to allow charge to dissipate and to create a stable image. The consistent nature
of the charge flow in an ion microscope (positive charge in and negative charge
out under all conditions) obviates the often difficult task of searching for the
charge equalizing beam voltage as is required in SEM. The ORION® PLUS
also can maintain this charge flow balance at high beam energy, bypassing the
trade-off between charge control and resolution necessary in SEM.
An example of this is seen in imaging of collagen fibers from the knee joint
of a mouse, as seen in the first image below. This sample, prepared by critical
point drying, was found to be challenging to image in SEM due to charge related
instabilities. In the ORION® PLUS it was possible to obtain a stable image, thus
more easily revealing detail on the banding in these fibers. There is also
charge neutralization capability available from a low energy electron flood
gun.
An example of non-damaging image acquisition is found in the investigation of
CHO (Chinese Hamster Ovary) cells. CHO cell lines are very common and important,
being utilized for example in drug discovery. The structure of the membranes and
of the finger-like structures, called filopodia, on these cells is related to
their biology – and thus to their behavior in pharmaceutical research. The ORION® PLUS
microscope has shown the ability, as seen in the second image below of critical
point dried cells, to provide superior image resolution and contrast. It is also
notable that it is possible to image the filopodia at high magnification without
shrinking them, which is a problem in SEM imaging.
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Figure 1. Collagen fibers Imaging in collaboration with
Dr. Claus Burkhardt, NMI (Stuttgart, Germany)
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Figure 2. Chinese Hamster Ovary (CHO) cells Imaging in
collaboration with Dr. Claus Burkhardt, NMI (Stuttgart, Germany)
The ORION PLUS Capabilitites
Material contrast, non-destructive imaging, charge control
Application
Imaging three dimensional biological structures
Source: "Imaging Biological Samples " by Carl Zeiss
For more information on this source, please visit Carl
Zeiss.