Which fixative would be most suitable if lipid preservation is required?

• A. Osmium Tetroxide
• B. Bouin's
• C. 70% Ethanol
• D. Acetone

Answer: (A)

Lipid preservation requires a fixative that stabilizes lipids rather than dissolving them. Osmium tetroxide reacts with the double bonds in unsaturated lipids, fixing and cross-linking the lipid-rich membranes while also staining them, which preserves the lipids’ structure and makes membranes visible—especially important for electron microscopy. Other fixatives mentioned tend to avoid lipids or even extract them: Bouin's preserves general tissue morphology but isn’t lipid-friendly; 70% ethanol and acetone are organic solvents that can dehydrate and extract lipids, leading to lipid loss rather than preservation. So the fixative best for maintaining lipid content is osmium tetroxide.