Neutral Red (CAS 553-24-2)

Neutral Red, with the chemical formula C15H16N4·HCl and a CAS number of 553-24-2, is a fascinating diazo dye known for its ability to permeate through cell membranes, primarily utilized in various scientific research contexts rather than medical or pharmaceutical applications. This chemical, appearing as a dark red crystalline powder, is soluble in water and becomes yellow upon dilution, but returns to red in acidic conditions, a property that makes it exceptionally useful in biological staining. In research, Neutral Red′s unique mechanism involves intercalating into cellular components, particularly targeting lysosomes and other acidic organelles. This characteristic enables its use in viability assays, such as the Neutral Red uptake assay, where it serves as a robust indicator of cell viability and proliferation. Cells can uptake Neutral Red by active transport mechanisms, and its accumulation within lysosomes or other acidic vesicles can be quantitatively measured, providing insights into cellular health and function. Furthermore, Neutral Red has been extensively used in environmental studies, especially in assessing the cytotoxicity of various chemicals on aquatic life. Its ability to act as a pH indicator also makes it useful in cell culture systems to monitor cellular metabolic activity indirectly. This dye′s versatility extends to its application in histochemistry and as a vital stain in microscopy, thereby enriching its utility in non-clinical scientific explorations.