Intracellular metabolic activity reduces blue, nonfluorescent resazurin to pink, fluorescent resorufin. This chemical conversion links cellular metabolism to an assay signal: greater production of resorufin indicates greater metabolic activity in the measured cell population. Researchers can then quantify the resulting change through fluorescence or absorbance to compare cellular viability across experimental conditions.
The signal primarily indicates the presence and metabolic activity of living cells rather than providing a direct count of individual cells. A stronger fluorescence or absorbance response is associated with more detectable metabolic activity in the population. Consequently, researchers should interpret results as an estimate of cellular viability or activity, especially when comparing treated and untreated conditions.
Resazurin reduction produces resorufin, which has a fluorescent signal and also changes the assay's color. Fluorescence measurement detects the emitted signal, whereas absorbance measurement evaluates the optical change associated with the conversion. Both approaches provide quantitative readouts for comparing conditions, allowing the assay to fit different experimental measurement strategies without requiring direct cell counting.
Researchers measure the resazurin-derived signal from cell populations exposed to different experimental conditions and compare the resulting fluorescence or absorbance values. Because the readout reflects metabolic activity, differences between conditions can indicate changes in cellular survival or health. This design supports evaluation of how an infectious agent or candidate treatment influences the measured population.
In immunology research, the assay helps estimate whether immune-cell populations remain viable and metabolically active under defined experimental conditions. Comparing signal levels between conditions can reveal changes in cellular health or survival without requiring researchers to count each cell individually. This makes the method useful when studying how experimental treatments or infectious agents affect immune-cell populations.
The method can be used to assess microbial growth as well as the effects of infectious agents on cells. It also supports testing candidate treatments by comparing metabolic readouts across experimental conditions. Depending on the population examined, the resulting signal can therefore inform studies of microbial viability, host-cell survival, or treatment-associated changes in cellular activity.