How is Congo red stain prepared?
Preparing the solutions for staining Congo Red powder dye solution (for staining acc. to the Highman method): 1% solution of Congo Red powder dye: • Dissolve 0.5 g of Congo Red dye in 50 ml of distilled/demi water. Add 50 mL of 100% ethanol. Filter before use.
How does Congo red stain amyloid?
Amyloid stained by Congo red is traditionally said to show apple-green birefringence in polarized light, although in practice various colors may be seen between accurately crossed polarizing filters, called polarizer and analyzer.
What does Congo red detect?
Staining with Congo Red dye (CR) is one of the major methods used to detect the amyloid structure of protein aggregates.
How do you use Congo red?
Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing. It is still used in histology to stain tissues for microscopic examination, and to serve as an acid-base indicator, since it turns red in the presence of alkalies and blue when exposed to acids.
Is Congo red a basic stain?
Congo red is an acid-base indicator dye. Such solvents may also change the aggregation or solvation states of the dye, with consequent modification in the colour of tissue components.
Where does Congo red stain?
amyloidosis
In histology and microscopy, Congo red is used for staining in amyloidosis, and for the cell walls of plants and fungi, and for the outer membrane of Gram-negative bacteria. Apple-green birefringence of Congo red stained preparations under polarized light is indicative of the presence of amyloid fibrils.
How do you make Congo red solution?
2.2. Preparation of Congo Red 1000 mg/L (stock solution) was prepared by dissolving 1 g of congo red in 1 Liter of distilled water.
How do you make a Congo red indicator?
Make a 1% solution of Congo red indicator by adding 1 g of Congo red to 100 mL of distilled or deionized water. Rinse the sponge (including new sponges) with water to remove residual soap, surfactants, or acids.
Is Congo red a negative stain?
The Congo Red Capsule stain is a modification of the nigrosin negative stain you may have done previously. The bacteria take up the congo red dye and the background is stained then with acid fuchsin dye.
What kind of stain is Congo red?
amyloid material
Congo red is still the standard stain used in most histopathology laboratories to identify amyloid material in tissues. The identification of Congophilic amyloid material is challenging because of multiple interfering factors.
Why is it called Congo red?
“Congo” red was introduced in Berlin in 1885 as the first of the economically lucrative direct textile dyes. Conclusions: The Congo red stain was named “Congo” for marketing purposes by a German textile dyestuff company in 1885, reflecting geopolitical current events of that time.
Is Congo red soluble in water?
It is an azo dye. Congo red is water-soluble, yielding a red colloidal solution; its solubility is greater in organic solvents. However, the use of Congo red has long been abandoned, primarily because of its carcinogenic properties.