Question

Viable cells (viability assay) are assayed by all of the following methods except 

• A. MTT/MTS/Resazurin assay
• B. Apoptosis assay
• C. ATP assay
• D. Protease marker assay

Answer 1

The Correct Option is B

To determine which method is not typically used to assay viable cells in a viability assay, let's examine each option provided:

1. MTT/MTS/Resazurin assay: These are colorimetric assays commonly used to assess cell metabolic activity, which correlates with the number of viable cells. These assays measure the reduction of tetrazolium salts (such as MTT or MTS) or the conversion of resazurin to a fluorescent product, indicating viable cells are present.
2. Apoptosis assay: Apoptosis assays are designed to detect apoptotic cells, which are dying, rather than viable ones. These assays identify markers of the apoptotic process, such as DNA fragmentation or caspase activation. Thus, it does not directly measure cell viability, but rather cell death.
3. ATP assay: ATP assays measure the level of ATP, which is indicative of metabolically active, viable cells, as ATP is a marker for cell energy. These are standard assays for assessing cell viability.
4. Protease marker assay: This assay is used to measure cell viability based on the measurement of protease activity released by cells with an intact membrane. The protease activity correlates with the number of viable cells.

From the analysis above, it is evident that the Apoptosis assay does not measure viable cells directly; instead, it measures dying or dead cells. Therefore, the correct answer is Apoptosis assay.