Agar-Gelatin for Embedding Tissues Prior to Paraffin Processing

Tissue Pre-Embedding Histologists often arrange tissue samples in a very specific orientation prior to paraffin embedding using a process known as pre-embedding. Pre-embedding has traditionally utilized molten agar that is poured over the tissue and which hardens to maintain the proper orientation of the tissue during subsequent embedding procedures. A shortcoming of using agar as the pre-embedding media is that certain tissues shrink during the embedding process, and the agar-based pre-embedding media limits tissue expansion during slide mounting, resulting in difficulties with the tissue sample adhering to the microscope slide. Jones and Calabresi have provided a simple solution to this challenge by using agar mixed with gelatin as a new pre-embedding media. The authors demonstrate that for central nervous system tissues, which tend to shrink during embedding, using agar-gelatin pre-embedding allows these tissues to completely expand when placed on a 42°C water bath prior to slide mounting. The gelatin ...