What type of medium is used with lipids?

• A. Synthetic resin
• B. Gelatin
• C. Agar
• D. Water

Answer: (A)

Lipids are prone to being dissolved or extracted during standard tissue processing that uses water-based or solvent-heavy steps, so to study them you need an embedding medium that preserves them by providing a non-aqueous, highly stable matrix. Synthetic resin embedding (such as epoxy or methacrylate resins) infiltrates dehydrated tissue and hardens to form a solid, non-aqueous block, which helps retain lipid droplets and membrane structures for subsequent thin-sectioning and imaging. Gelatin, agar, and water are hydrophilic and would not provide the same lipid preservation or the needed structural support during sectioning, leading to loss or distortion of lipids. Thus, the medium best suited for lipids is a synthetic resin embedding medium.