What measure can prevent tissue loosening from the chuck during frozen sectioning?

• A. Applying embedding medium to a warm chuck
• B. Cooling the chuck further
• C. Rinsing the tissue with water before embedding
• D. Using a different embedding medium after freezing

Answer: (A)

In frozen sectioning, keeping the tissue firmly attached to the chuck is essential to prevent movement during cutting. The embedding medium acts as an adhesive between the tissue and the chuck. Applying embedding medium to a warm chuck allows the medium to spread well and wet the surface and the tissue cleanly, eliminating air gaps. When the block is placed in the cryostat and begins to freeze, the medium solidifies around the tissue, locking it in place so it won’t loosen as the blade passes by. If the chuck is too cold, the medium may lock up or fail to wet the surface properly, increasing the chance of tissue loosening. Rinsing with water or changing embedding media after freezing doesn’t address the adhesion at the mounting stage, and cooling the chuck further tends to reduce adhesion.