A relatively unknown but very gentle and effective method for decalcification is chelation with ethylenediaminetetraacetic (EDTA) acid. Chelating agents (EDTA is most common) are organic compounds that bind to certain metals and calcium ions. Chelation is not commonly used for rapid and routine processing.
EDTA properties:
- Preferred pH of solution is neutral to slightly acidic
- Size of tissue must be small to be effective
- Very slow decalcifier, so ample time is required (from days to weeks)
- Gentle with minimal cellular damage
- Good for tissue that requires enzyme testing, FISH, and IHCs
- Solution must be changed frequently
- Once calcium binds to EDTA, decalcification stops, and fresh solution is needed to continue the process
