Answer:
acid
base
Step-by-step explanation:
Neutral red dye is widely used for various histological and cytological tests.
The neutral red cell cytotoxicity test is one of the methods commonly used to detect cell viability or the cytotoxicity of drugs. The principle of this test is based on the detection of viable cells via the absorption of the neutral red dye. Neutral red is a Eurhodin dye that stains lysosomes in viable cells. Viable cells can take up neutral red via active transport and incorporate the dye into their lysosomes, but non-viable cells cannot take up this chromophore. Therefore, after washing, viable cells can release the incorporated dye under acidified extraction conditions.
The amount of dye released can be used to determine the total number of viable cells or the cytotoxicity of the drug. The neutral red absorption test provides a quantitative measure of the number of viable cells and can be measured at an OD of 540 nm.
However; Neutral red dye changes colour depending on the pH of its surroundings. The dye is pink-red in a(n) acid and changes colour to orange-yellow in a(n) Base.