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One of the most commonly asked questions I have received lately is "when using tissue marking dyes (TMD), is it better to mordant or not to mordant?" For those who don't currently use a mordant, mordants help the dyes to adhere to tissues and are applied 10-15 seconds before the marking dye. Adding this step adds costs and time on the front end but could really help ensure better results on the back end.
So back to my original question. To mordant or not to mordant? I think the answer lies in the ultimate goal, which is to ensure dyes will withstand the rigors of tissue processing. So like everything else in histology, I would say "it depends."
Most tissue marking dye manufacturers' Instruction for Use sheets indicate a mordant is not required for optimal performance. However, certain tissues may benefit from the use of a mordant. Specifically, fatty tissues which are amphoteric (neutrally charged). The use of a mild acetic solution prior to applying the Tissue Marking Dye will change the amphoteric sites on the tissues to a negative charge (anionic), which attracts the positively charged (cationic) Tissue Marking Dye and a strong ionic bond is formed. Once formed, these bonds are resistant to the exposure of tissue processing procedures and chemicals.
If you decide you want to try a mordant but have additional questions, please don't hesitate to reach out and let me know. I would be happy to help!
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