Neutral red

{{chembox

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 448702349

| Name = Neutral red

| ImageFile = Neutral red Formula V.1.svg

| ImageSize = 300px

| ImageFileL1 = Sample of neutral red.jpg

| ImageSizeL1 = 130

| ImageCaptionL1 = Solid Neutral Red

| ImageFileR1 = Neutral Red Aqueous Solution.jpg

| ImageSizeR1 = 130

| ImageCaptionR1 = Neutral Red Aqueous Solution

| ImageName = Neutral red

| IUPACName = N²,N²,7-Trimethylphenazine-2,8-diamine—hydrogen chloride (1/1)

| OtherNames = 3-Amino-7-dimethylamino-2-methylphenazine hydrochloride
Toluylene red

|Section1={{Chembox Identifiers

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 10634

| ChEBI_Ref = {{ebicite|changed|EBI}}

| ChEBI = 86370

| PubChem = 11105

| EC_number = 209-035-8

| UNII = 261QK3SSBH

| InChI = 1/C15H16N4.ClH/c1-9-6-13-15(8-11(9)16)18-14-7-10(19(2)3)4-5-12(14)17-13;/h4-8H,16H2,1-3H3;1H

| InChIKey = PGSADBUBUOPOJS-UHFFFAOYAB

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/C15H16N4.ClH/c1-9-6-13-15(8-11(9)16)18-14-7-10(19(2)3)4-5-12(14)17-13;/h4-8H,16H2,1-3H3;1H

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = PGSADBUBUOPOJS-UHFFFAOYSA-N

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 553-24-2

| SMILES = Cl.n1c3c(nc2c1cc(c(c2)N)C)cc(N(C)C)cc3

}}

|Section2={{Chembox Properties

| Formula = C₁₅H₁₇N₄

| MolarMass = 288.78 g/mol

| Density =

| MeltingPtC = 290

| BoilingPt =

}}

|Section7={{Chembox Hazards

| GHSPictograms = {{GHS06}}{{GHS07}}{{GHS08}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|301|315|319|335|341}}

| PPhrases = {{P-phrases|201|202|261|264|270|271|280|281|301+310|302+352|304+340|305+351+338|308+313|312|321|330|332+313|337+313|362|403+233|405|501}}

}}

}}

{{pH indicator|indicator_name=Neutral red|low_pH=6.8|high_pH=8.0|low_pH_color=red|low_pH_text=white|high_pH_color=yellow}}

Neutral red (toluylene red, Basic Red 5, or C.I. 50040) is a eurhodin dye used for staining in histology. It stains lysosomes red.{{cite book |last=Winckler |first=Jürgen |date=1973 |title=Vitalfärbung von Lysosomen und anderen Zellorganellen der Ratte mit Neutralrot |trans-title=Vital staining of lysosomes and other cell organelles of the rat with Neutral red |series=Progress in Histochemistry and Cytochemistry |lang=de |volume=6 (3) |issue=3 |pages=1–91 |publisher=Gustav Fischer Verlag |doi=10.1016/S0079-6336(74)80001-X |isbn=3-437-10353-9 |pmid=4142096}} It is used as a general stain in histology, as a counterstain in combination with other dyes, and for many staining methods. Together with Janus Green B, it is used to stain embryonal tissues and supravital staining of blood. It can be used for staining the Golgi apparatus in cells and Nissl granules in neurons.

In microbiology, it is used in the MacConkey agar to differentiate bacteria for lactose fermentation.

[https://medium.com/@GSPChem/neutral-red-8d9c51584fa Neutral red] can be used as a vital stain.{{cite journal |last1=Repetto |first1=Guillermo |last2=del Peso |first2=Ana |last3=Zurita |first3=Jorge L. |date=2008 |title=Neutral red uptake assay for the estimation of cell viability/cytotoxicity |journal=Nature Protocols |volume=3 |issue=7 |pages=1125–1131 |doi=10.1038/nprot.2008.75 |pmid=18600217|s2cid=24676983 }} The Neutral Red Cytotoxicity Assay was first developed by Ellen Borenfreund in 1984. In the Neutral Red Assay live cells incorporate neutral red into their lysosomes. As cells begin to die, their ability to incorporate neutral red diminishes. Thus, loss of neutral red uptake corresponds to loss of cell viability.{{cite journal |last1=Borenfreund |first1=Ellen |last2=Puerner |first2=James A. |date=1984 |title=A simple quantitative procedure using monolayer cultures for cytotoxicity assays (HTD/NR90) |journal=Journal of Tissue Culture Methods |volume=9 |issue=1 |pages=7–9 |doi=10.1007/BF01666038}} The neutral red is also used to stain cell cultures for plate titration of viruses.

Neutral red is added to some growth media for bacterial and cell cultures. It usually is available as a chloride salt.

Neutral red acts as a pH indicator, changing from red to yellow between pH 6.8 and 8.0.