Type and quality of paraffin wax is important for constructing tissue
Tissue technology allows the representation of hundreds of tissue samples on a standard microscope slide. This is achieve by arraying small cores (0.6 mm in diameter) of paraffin wax embed tissue samples in a recipient wax block. Sections cut from the array can then be assessed according to standard protocols.
suitable quantity of wax in tissue
First, it was suggested that when the recipient blocks were made, insufficient wax was poured through the cassette, resulting in weak adhesion between the block and the cassette.
However, we ensure that the mold, including the back of the cassette, was full and that the wax level was not allow to recede during cooling. Second, rough handling of the arrays could weaken the wax, but we do not believe that this occurred.
Third, temperature fluctuations may play a role. Although arrays were construct and stored at ambient temperature, they were cooled after every 10&15 sections cut, according to standard procedures.
We no longer cool arrays during sectioning and quality remains comparable to publish studies. Fourth, sections were cut along the length of the array, which may theoretically exert excessive shearing forces on the wax and increase its potential to fracture.
Consequently, we now section across the width of the array. Fifth, cores may have been arrayed too deeply into the recipient block, weakening the wax at the cassette surface. Cores are now place at least 1 mm above the cassette. Sixth, prolonged heating of wax above its melting point may compromise its quality. However, our wax is heated to its melting point of 60°C and kept molten for no longer than one week.
quality of wax
Finally, the quality of wax used to make the recipient block is important. The wax that we had used initially did not contain plastic .
Paraffin is widely use in tissue processing, particularly in histology and pathology, for the preservation of tissue samples. Here’s an overview of how paraffin is involved in tissue preparation:
1. Tissue Fixation
- Before embedding tissues in paraffin, they need to be fixed to preserve their structure and prevent decay. Formaldehyde (formalin) is commonly used as a fixative.
- The fixation process ensures that the tissue maintains its morphology, preventing enzymatic or bacterial degradation.
2. Dehydration
- After fixation, the tissue sample is dehydrate by passing it through a series of alcohol solutions with increasing concentrations (typically starting from 70% alcohol to 100% alcohol).
- This removes the water content from the tissue, which is necessary for paraffin embedding, as paraffin is hydrophobic and will not infiltrate tissues that still contain water.
3. Clearing
- The alcohol is then replaced with a clearing agent, such as xylene or toluene. These solvents are miscible with both alcohol and paraffin, allowing the paraffin to infiltrate the tissue later.
- Clearing agents remove the alcohol and prepare the tissue to accept paraffin by making the tissue transparent.
4. Infiltration with Paraffin
- After clearing, the tissue is infiltrated with molten paraffin wax, usually at a temperature around 60°C (140°F). This step ensures that the paraffin completely permeates the tissue and hardens into a solid block.
- The tissue is typically placed in several changes of molten paraffin to ensure full infiltration.
5. Embedding
- Once the tissue is adequately infiltrate with paraffin, it is place in a mold, and additional molten paraffin is poured over it.
- The mold is cooled to solidify the paraffin, encasing the tissue in a firm block, which can then be cut into thin sections for further examination.
6. Sectioning
- The paraffin-embedded tissue block is cut into very thin slices (usually 4-10 microns thick) using a microtome.
- These thin sections are then place on glass slides for further analysis, such as staining and microscopic examination.
7. Deparaffinization (for staining)
- Before staining or further processing, the paraffin is removed from the tissue sections. This is done by using xylene or other deparaffinizing agents.
- The sections are then rehydrated, often through a series of alcohol solutions, before applying stains.
Importance of Paraffin in Tissue Processing
- Paraffin embedding is crucial for preserving the structural integrity of tissue samples and allows for the creation of thin sections for microscopic analysis.
- It also facilitates the long-term storage of tissue specimens, which can be studied later for diagnostic, research, or educational purposes.
In summary, paraffin is integral to the preservation and preparation of tissue samples for histological examination. It ensures tissue integrity, allows for detailed microscopic examination, and supports the long-term storage of biological specimens.
