Tissue processing is the process in which water is removed from tissue cells and replaced with a medium to solidify its form and structure. This is a pivotal stage in this histology process for diagnosis and research as it enables lab technicians to examine tissue specimens in their correct form and enables thin sections to be cut on a microtome.
During this tissue processing the tissue sample will go through a series of steps automatically in a tissue processor, to preserve its cellular details and support its structure. Tissue processors are able to handle larger specimen numbers, process more quickly, and produce better-quality results. Tissue processors offer two different methods of introducing reagents to the specimen, Carousel Tissue Processors are known for specimen transfer, this is where the cassettes are transferred from station to station in a “dip and dunk” motion in a rotary configuration. Alternatively, fluid-transfer processors, such as the MTM Vacuum Tissue Processor, pumps the reagent in and out of the specimen whilst the sample/cassette remains in a chamber.
Steps of Tissue Processing
Dehydration – Alcohol
Alcohols (e.g. ethanol, methanol, isopropanol and butanol) are used to dehydrate the tissue sample, removing the water as it is incompatible and immiscible with paraffin wax. Dehydration of the tissue is commonly carried out by immersing the specimen in a series of ethanol (alcohol) solutions of increasing concentration from typically 70% to 100% until pure alcohol. The gradual increase of alcohol prevents damage or distortion of the tissue.
Clearing – Xylene
The alcohol is dissolved and replaced with a clearing agent such as Xylene, that is miscible with both alcohol and paraffin wax. The clearing agent also removes a substantial amount of fat from the tissue, which otherwise presents a barrier to wax infiltration in the next stages of tissue processing.
Infiltration – Paraffin Wax
The tissue is then infiltrated with molten paraffin wax. This step ensures that the wax permeates the tissue, filling all spaces and providing the necessary support. Several changes of paraffin wax are required to displace the clearing agent completely. The vacuum within fluid-transfer processors helps enhance paraffin infiltration, speeding up the process and providing better results. Following this, the wax is cooled, solidifying to hold the cellular structure, forming the right consistency for sectioning.
UltraPlast meets the required melting point, melting at a temperature of between 54 to 57 ºC. However, we can also supply paraffin wax with a higher melting point to accommodate to your process, lab conditions or specific tissue processor and embedding centre in place.
Why Paraffin Wax?
Support
Paraffin Wax provides a solid medium that maintains the integrity of the tissue structure during the sectioning process without causing compression or distortion to the tissue.
Ease of Sectioning
The chemical compound of the paraffin wax allows the wax to solidify within the specimen and be embedded into a solid block using a tissue mould. This block is the perfect consistency to cut thin sections by using a microtome that maintains the correct structure of the specimen.
Preservation
It helps preserve cellular details by stabilising the tissue. This allows for margins, stains and cell abnormalities to be identified under the microscope further down the line.
Versatile
A wide range of paraffin waxes are available with different melting points, and various consistencies (extra polymers and elasticity) to accommodate different processes, climates and machines.
To learn more about our range of wax visit Paraffin Wax or speak to our team to learn more about our UltraPlast Paraffin Wax at +44 (0) 844 8080 900 or labsupplies@solmedialtd.com.