Embedding in Resins for Immunocytochemistry
Biological specimens are embedded in resin so that they can be thin sectioned. Many different resin formulas are currently available and all have been used for post-embedding labeling (i.e. where antibodies are applied to thin sections of the tissue) with variable results. Specialized resin formulas have been developed specifically for use in immunocytochemistry. These include the Lowicryl resins, LR White and LR Gold, Unicryl and MonoStep. They all have low viscosity and can be polymerized, at low temperatures, with ultra violet (UV) light.
The most common embedding protocol for these resins is called the progressive lowering of temperature (PLT) method where the sample is progressively cooled during the dehydration steps. The specimens are then transferred to resin and the blocks are polymerized, at low temperature, by exposure to UV light.
An alternative method for embedding specimens in these resins is by freeze substitution. This method consists of freezing the specimen and then substituting the frozen water in the specimen with a liquid solvent. Follow the following links for more details on the theory of freeze substitution and for a simple protocol of freeze substitution
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