Laser microdissection

Laser Microdissection is an extraction process to dissect specific tissue for analysis or research.

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Extraction process

A laser is coupled into a microscope and focuses onto the tissue of the slide. By movement of the laser by optics or the stage the focus follows a trajectory which is predefined by the user. This trajectory, a so called Element, is then cut out and separated from the adjacent tissue. After the cutting process, an extraction process has to follow if an extraction process is desired.

Theoretically, there are several ways to extract tissue from a microscope slide with a histopathology sample on it:

• Press a sticky surface onto the sample and tear out. This will extract the desired region, but also bears the chance to carry particles or unwanted tissue on the surface, because an allround sticky surface is not selective.
• Melt a plastic membrane onto the sample and tear out. The heat is introduced by an, e.g., red or IR laser onto a membrane stained with an absorbing dye. As this adheres the desired sample onto the membrane, as with any membrane that is put close to the histopathology sample surface, there might be some debris extracted. Another danger is the introduced heat: Some molecules like DNA, RNA, or protein don't allow to be heated too much or at all for the goal of being isolated as purely as possible.
• Transport without contact. There are two different approaches:

1. Transport simply by gravity using an upright microscope or
2. Transport by Laser Pressure Catapult.

As laser light introduces energy to a sample, it is possible to accelerate the dissected element by laser pulse on the element and collect it into a cup.

• Palm - Carl Zeiss commercial non-contact Laser Microdissection and Imaging Workstations