Congo Red

Description

“Congo red” is not the name of a famous African explorer, but a dye that dates to 1883. It was synthesized by P. B?ttiger 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.
Recently, I. A. Buhimschi and co-workers at Nationwide Children’s Hospital (Columbus, OH) found a new use for Congo red. Taking a cue from Alzheimer’s disease researchers who found that the dye can be used to detect misfolded proteins, they showed that proteins in the urine of pregnant women who suffer from preeclampsia cause Congo red to change color. An Alzheimer’s researcher not involved in the study says, “The diagnostic potential is really big—depending on how specific it turns out to be for preeclampsia.”

Chemical properties

C.I. Direct red 28(Congo Red) is an odorless, brownish-red powder.Soluble in water; solubility =25 g/L at25℃.

The Uses of Congo Red

Congo red is useful for staining and visual detection of amyloid deposits. It inhibits the accumulation of the scrapie-associated, protease-resistant isoform of protein PrP without affecting the metabolism of the normal isoform.

The Uses of Congo Red

Dye, medicine (diagnostic aid), indicator, biological stain.

The Uses of Congo Red

• Congo red has been used as a histochemical stain for the quantification of amyloid deposits in brain tissues.
• It has been used as a cell wall inhibiting agent in fungus Cryptococcus neoformans.
• It has also been used to study microstructural details in the cell walls of raw potato and fried potato using confocal microscopy.

Definition

ChEBI: An indicator dye that is blue-violet at pH 3.0 and red at pH 5.0.

Biochem/physiol Actions

Congo red is a benzidine-based anionic diazo dye. It is a histological dye which binds to many amyloid proteins and is used for the quantification of amyloid β-peptide aggregation. Congo red also interacts with β-D-glucans, polysaccharides containing continuous β-(1→4)-linked D-glucopyranosyl units and some hemicellulosic galactoglucomannans.

Safety Profile

Human poison by ingestion with cardovascular effects. Experimental poison by intravenous route. An experimental teratogen. Experimental reproductive effects. An eye irritant. Mutation data reported. When heated to decomposition it emits very toxic fumes of NOx, SOx, and Na2O

Potential Exposure

It is used as an indicator dye, a biological stain; a diagnostic aid in medicine; and a dye for fabric and paper.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. If victim is conscious, administer water ormilk. Do not induce vomiting.

storage

Room temperature

Shipping

UN3143 Dyes, solid, toxic, n.o.s. or Dye intermediates, solid, toxic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required

Purification Methods

Crystallise the dye from aqueous EtOH (1:3). Dry it in air. [Beilstein 6 I 342.]

Properties and Applications

Standard	Acid Resistance	Alkali Resistance	Light Fastness	Soaping		Water
				Fading	Stain	Fading	Stain
ISO	1	3	1	2		2
AATCC	1	3	2	1		3

Incompatibilities

Contact with oxidizers may cause fire and explosion hazard. Incompatible with strong acids; reducing agents.