Common methods for neutral fat staining include Sudan I, Sudan III, Sudan IV, Sudan Black B, Oil Red O staining, etc. The mechanism of lipid staining with Sudan dyes is generally considered to be purely physical liposolubility and adsorption. Since Sudan dyes have a higher solubility in lipids than in organic solvents, the dyes transfer from the staining solution to the stained lipids during staining, rendering the lipids the color of the staining solution. Saturated Sudan alcoholic solution is mainly used to demonstrate fatty degeneration of tissues and organs and abnormal deposition of lipoids, which often occurs in parenchymal organs such as the liver, kidney and heart, with numerous neutral fat droplets appearing in cells; it is also used to identify and diagnose tumors occurring in adipose tissue and their properties.
Procedures (for reference only):
1. Prepare frozen sections of fresh tissue at a low temperature, generally -20°C ~ -25°C. For lipoma samples, the temperature should be adjusted to -30°C.
2. Cut frozen sections at 5~10 μm (6~8 μm is optimal), and mount them on glass slides.
3. Rinse briefly with 70% ethanol.
4. Immerse in saturated Sudan alcoholic solution for 1–2 min.
5. Wash away excess staining solution with 70% ethanol.
6. Rinse with distilled water for 1 min.
7. Perform downstream experiments according to specific experimental requirements.
Staining Result:
Neutral fat – orange-red
Precautions:
1. For fat staining, specimens should not be fixed with ethanol-containing fixatives or prepared as paraffin sections; frozen sections are required.
2. Dye precipitation must be prevented during staining. Therefore, sections should be sealed when immersed in the staining solution to avoid contact with circulating air, which can cause precipitation due to solvent volatilization.
3. Frozen sections stain easily; overstaining should be avoided during counterstaining.
4. Sudan dyes fade easily and should be stored in a sealed container.
5. For your safety and health, please wear a laboratory coat and disposable gloves during operation.
6. This product is for research use only; strictly prohibited for other purposes.
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