Methylene Blue Chloride, C.I. 52015, is a cationic phenothiazinium dye used in histological staining and microscopy workflows. Its positively charged chromophore interacts with negatively charged cellular constituents, including nucleic acids, making the dye useful for visualization of nuclei and other nucleic acid-rich structures.
Synonyms: Basic Blue 9; Methylthioninium chloride; Tetramethylthionine chloride; 3,7-Bis(dimethylamino)phenothiazin-5-ium chloride.
Methylene blue is used both as a primary stain and as a counterstain in multistep staining procedures. Staining intensity and selectivity depend on specimen preparation, dye concentration, staining time, pH, and the composition of the material being examined.
Key Properties
- Cationic phenothiazinium dye
- Color Index Number: C.I. 52015
- Also known as Basic Blue 9 and methylthioninium chloride
- Linear formula: C16H18ClN3S · xH2O
- Molecular weight: 319.85 g/mol on an anhydrous chloride basis
- Appearance: dark green crystals or powder with a bronze luster
- Water solubility: approximately 400 g/L
- Catalog number: 04220
- Storage: room temperature
Applications
Histology & Tissue Staining
Methylene blue is used in histological staining workflows to provide contrast among cellular and tissue structures. Its affinity for anionic cellular constituents makes it particularly useful where nuclear and nucleic acid-rich structures require visualization.
Nuclear & Nucleic Acid Staining
The cationic dye interacts with negatively charged sites in DNA, RNA, and other cellular components. Methylene blue can therefore be used in staining methods for nuclei and nucleic acid-containing structures, although staining intensity is influenced by fixation, specimen preparation, and staining conditions.
Counterstaining in Acid-Fast Methods
Methylene blue is used as a counterstain in acid-fast staining procedures, including Kinyoun-type methods. Following primary staining and acid-alcohol decolorization, methylene blue provides contrast for material that does not retain the primary acid-fast stain.
Compatibility & Bonding Considerations
- Cationic character promotes interaction with negatively charged cellular and macromolecular sites
- Staining response depends on dye concentration, pH, ionic environment, specimen fixation, and staining time
- Methylene blue is not intrinsically specific for DNA or RNA and can interact with multiple anionic cellular constituents
- Fixation and specimen-processing conditions can influence accessibility of dye-binding sites
- When used as a counterstain, final contrast depends on the preceding staining and differentiation steps
Staining intensity should be interpreted within the context of the complete staining procedure rather than as a direct quantitative measure of nucleic acid or cellular-component concentration.
Application Tips
- Use the dye concentration specified by the validated staining procedure
- Keep staining time, specimen fixation, and section thickness consistent when comparing samples
- Maintain consistent solution conditions when comparing staining intensity across specimens
- Include appropriate positive and negative controls when staining patterns are used for comparative interpretation
- For multistep staining procedures, standardize decolorization, rinsing, and counterstaining times to maintain reproducible contrast
Handling & Storage
- Store at room temperature in a cool, well-ventilated location
- Keep the container tightly closed when not in use
- Avoid generating or breathing dust
- Avoid contact with skin and eyes
- Wear protective gloves, safety glasses, and suitable protective clothing
- Use in a chemical fume hood or other appropriately ventilated laboratory area
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FAQ
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1. What is Methylene Blue, C.I. 52015, used for?
Methylene blue is used in histological and laboratory staining workflows for visualization of nuclei, nucleic acid-rich cellular structures, and other negatively charged cellular components. It is also used as a counterstain in selected multistep staining procedures.
2. What does C.I. 52015 mean?
C.I. 52015 is the Colour Index designation for methylene blue. The dye is also known as Basic Blue 9 and methylthioninium chloride.
3. Does methylene blue stain DNA and RNA?
Methylene blue can interact with nucleic acids because its cationic chromophore associates with negatively charged sites in DNA and RNA. The dye is not specific exclusively to either nucleic acid, and observed staining also depends on specimen preparation and staining conditions.
4. Is methylene blue used as an acid-fast counterstain?
Yes. Methylene blue is used as a counterstain in acid-fast staining methods such as the Kinyoun procedure, where it provides contrast after primary staining and acid-alcohol decolorization.
5. What are common synonyms for methylene blue?
Common names include Basic Blue 9, methylthioninium chloride, tetramethylthionine chloride, and 3,7-bis(dimethylamino)phenothiazin-5-ium chloride.
Safety & Documentation
Methylene blue chloride is harmful if swallowed or inhaled and causes skin irritation. The current Safety Data Sheet also classifies it as suspected of causing cancer and suspected of damaging fertility or the unborn child. Use appropriate laboratory ventilation and personal protective equipment, and refer to the product Safety Data Sheet (SDS) for complete handling, storage, first-aid, and disposal guidance.
