Fixation of Frozen Tissues

Specialty fixatives, such as Osmium tetroxide, which is used primarily in electron micrography and acetone, is used in fixation of frozen sections. Others used for research purposes on specific tissue, organs or even whole organisms are not discussed in this publication. 

If no other histochemical techniques are needed, fresh tissue can be used. The block must be frozen quickly without cracking. Tissue is cut in small blocks with a new razor blade (washed in soap to remove oil). An alternative to the method below is freezing tissue on aluminum foil on top of dry ice and surrounding with crushed dry ice. However, the perimeter of the tissue is usually poorly preserved with this method. For RNA detection, DEPC is included at 0.02% in the subbing and fixation solutions. Poly-L-lysine coating may be superior at temperatures > 50°C since gel from gel-coated slides may detach at higher hybridization temperatures. It is convenient to use only some of the slides for immediate hybridization and store the rest for future reference. 

Fresh frozen tissue - samples with no fixation are frozen and sectioned gives distorted the morphology because no cross linking fixative and components of the tissue can wash out of the section. 

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