Answer:
That the material can be mixed with the original tissue
Explanation:
The biomaterial has the idea to be mixed with the original tissue, due is going to grow (if it is based in cells) or is going to attach to the biological tissue, so the H&E method can be confused. The hematoxylin is going to stain the nuclei of the cells meanwhile the eosin is going to stain the extracellular matrix and cytoplasm, so, if the biomaterial is mixed in the original tissue, can be confused the exactly boundary among the biomaterial and the biological tissue.
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