Laser microdissection

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Laser Microdissection is an extraction process to purify tissue for research or recultivation.

[edit] In General

A laser is coupled into a microscope and focuses onto the tissue of the slide. By movement of 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. We will refer to this portion of the tissue as the element in the rest of the article. 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 trear 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. As laser light introduces energy to a sample, it is possible to accelerate the dissected element by a single, last laser pulse on the rim of the element. This effect is called the Laser Pressure Catapult. Acceleration can be achieved from the microscope slide upwards, if an inverted microscope is used. As debris is held by gravity down on the slide, only the elements lift up and are caught in a receptacle. This receptacle is usually the cap of a microfuge tube. Those caps can be filled with buffer, medium in the case of living cells, or processing liquid. Moreover, if the cap is pre-filled with a certain amount of a biological inert silicone and leaving room for processing liquid also, elements can be transported into the cap and collected to higher amounts. If no processing liquids are present, e.g., tissue for RNA extraction can be collected in dryness.

[edit] External Links

• Core Unit Chip Applications, Jena employing LMPC
• Lucy Whittier Molecular & Diagnostic Core Facility employing LMPC
• Carl Zeiss commercial non-contact Laser Microdissection and Imaging Workstations
• MMI Molecular Machines & Industries commercial adhesive-surface Laser Microdissection systems