What is the purpose of Congo red dye?

What is the purpose of Congo red dye?

Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing.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.

How does Congo red staining work?

The Congo red staining principle is based on the formation of hydrogen bridge bonds with the carbohydrate component of the substrate. Congo red is an anionic dye and is capable of depositing itself in amyloid fibrils, which then exhibit a conspicuous dichroism under polarized light.

Is Congo red a basic dye?

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.

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.

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.

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 is Congo red stain prepared?

Is Congo red cationic or anionic?

Congo red (CR) is a benzidine-based anionic diazo dye that can cause allergic reactions and can be metabolized to benzidine, a carcinogenic product19. Depending on pH, various molecular structures of CR can be present in aqueous solution20, which hinders its elimination.

What type of dye is Congo red?

azo dye
Congo red is an organic compound, the sodium salt of 3,3′-([1,1′-biphenyl]-4,4′-diyl)bis(4-aminonaphthalene-1-sulfonic acid). It is an azo dye.

Is Congo Red cationic or anionic?

Does all amyloid stain with Congo red?

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.

Does Congo Red change pH?

“Congo red” is not the name of a famous African explorer, but a dye that dates to 1883. Böttiger as a textile dye, but it subsequently became more important as a pH indicator. It colors aqueous solutions blue below pH 3.0 and becomes red above pH 5.0.

What is Congo red stain used to test for?

1 Congo red stain is the gold standard for the demonstration of amyloid in tissue sections 2 It is used to evaluate the presence and extent of amyloidosis in different organs 3 Common diseases for Congo red stain include primary amyloidosis, AL amyloid seen in plasma cell dyscrasias, AA amyloid associated with inflammatory conditions

What is the pathophysiology of Congo red?

Congo red. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainscongored.html. Accessed September 10th, 2021. Common diseases for Congo red stain include primary amyloidosis, AL amyloid seen in plasma cell dyscrasias, AA amyloid associated with inflammatory conditions

Why is Congo red staining of fibril proteins so specific?

The specificity of this staining results from Congo red’s affinity for binding to fibril proteins enriched in β-sheet conformation.

What are the side effects ofcongo red?

Congo red is potentially toxic. It can reduce serum protein concentration and cause platelet aggregation, thrombocytopenia, and disseminated microembolism (Tschopp et al., 1971, Giger et al., 1974).