What is Celloidin?
Celloidin is a purified form of nitrocellulose used extensively in histology for embedding tissue samples. It is known for its excellent properties that preserve tissue architecture and allow for thin sectioning. Celloidin is particularly useful for specimens that are too delicate for conventional
paraffin embedding techniques.
Preservation of tissue morphology: Celloidin maintains the integrity of tissue structures, which is crucial for accurate histological analysis.
Flexibility: Celloidin-embedded tissues are less brittle than paraffin-embedded tissues, reducing the risk of damage during sectioning.
Compatibility: It is suitable for a wide range of staining techniques, including
Hematoxylin and Eosin (H&E) staining, as well as special stains.
Dehydration: Tissues are dehydrated through a series of graded alcohols to remove water, which can interfere with celloidin infiltration.
Infiltration: The tissue is then infiltrated with celloidin, typically dissolved in a mixture of alcohol and ether, over several days to ensure thorough penetration.
Hardening: The infiltrated tissue is hardened by exposing it to chloroform vapors or by immersing it in a chloroform-alcohol solution.
Sectioning: Once hardened, the tissue block can be sectioned using a
microtome equipped for celloidin-embedded specimens.
Time-consuming: The embedding process is more time-consuming compared to paraffin embedding, requiring several days to weeks for complete infiltration and hardening.
Handling and Safety: Celloidin solutions are flammable and require careful handling and storage. Additionally, the use of chemicals like chloroform presents health hazards.
Section Thickness: Sections obtained from celloidin-embedded tissues are generally thicker (10-20 micrometers) compared to paraffin sections, which can range from 3-5 micrometers.
Neuropathology: Celloidin is preferred for embedding
nervous tissue due to its excellent preservation of delicate structures.
Ophthalmic Pathology: It is also used for embedding
eye tissues, ensuring the fine details of the retina and other ocular structures are maintained.
Bone and Cartilage: Celloidin is effective in embedding hard tissues like bone and cartilage, which are challenging to process with paraffin.
Conclusion
In summary, celloidin is a valuable embedding medium in histology, offering distinct advantages for preserving tissue morphology and flexibility during sectioning. While it has some limitations, its applications in neuropathology, ophthalmic pathology, and hard tissue embedding make it an indispensable tool for certain histological analyses. Proper handling and adherence to safety protocols are essential when working with celloidin to ensure accurate and safe results.
