Tissue processors automate the process of preparing tissue samples for microscopic examination. This crucial step involves a series of treatments to preserve the tissue and make it suitable for embedding in paraffin wax, allowing for thin sectioning and staining.
The Three Main Steps of Tissue Processing
The Leica TP1020, and similar machines, systematically guide tissue samples through three essential stages:
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Dehydration: This step removes water from the tissue. Water interferes with the infiltration of paraffin wax, which is necessary for embedding. This is typically achieved using a graded series of alcohols, starting with low concentrations and gradually increasing to absolute alcohol (100%).
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Clearing: After dehydration, the alcohol needs to be removed. This is done using a clearing agent, most commonly xylene. Xylene makes the tissue transparent and prepares it for paraffin wax infiltration.
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Infiltration: This is the final step where molten paraffin wax replaces the xylene in the tissue. This embedding medium provides support for the tissue, allowing for the creation of thin sections suitable for microscopic analysis. The wax solidifies around the sample, creating a sturdy block for sectioning on a microtome.
The Automated Process
Automated tissue processors like the Leica TP1020 automate this entire procedure. They use a series of containers filled with the different reagents (alcohols, xylene, paraffin wax). The tissue cassettes are moved from one container to the next, spending a specific amount of time in each reagent according to a pre-programmed schedule. This automated process ensures consistent and even processing across multiple samples, improving efficiency and reproducibility.
Example: A typical processing schedule might include several changes in alcohol concentrations (70%, 80%, 90%, 100%), followed by xylene changes and then several paraffin wax changes to ensure complete infiltration.
