Cytotoxicity test

Why don’t we use RPMI medium with phenol red in the cytotoxicity test using DMSO?

• Phenol red is too toxic.

• Phenol red interferes with the reaction of DMSO.

• Phenol red interferes with the color of soluble XTT.

• Phenol red inhibits the reaction to from soluble XTT.

What is the purpose of using PBS for filling in wells around the tested wells in cytotoxic assay?

• to control cell growth

• to prevent contamination

• to activate tested reagent

• to provide humid environment

What is XTT compound?

• Tetrazolium salt

• Soluble formazan

• Insoluble formazan

• Succinate tetrazolium dehydrogenase

XTT assay is used for measuring

• cell death

• cell viability

• total number of cells

• metabolically active cells

In XTT assay, the intensity of optical density (OD) is proportional to the toxicity of a tested compound to the cells.

• True

• False

The difference between XTT and MTT assays is that XTT is a one-step assay whereas MTT is not.

• True

• False

 In this experiment, what is the reason for having wells that contain no cells but various concentrations of DMSO (DMSO control)?

• To provide humid environment

• To confirm that DMSO is sterile

• To provide background optical density

• To compare optical density with the medium control

According to Chou T-C and Talalay P (1984), a graph is plotted as shown. Which of the following is correct?

• X = log (fa/fu)

• Y = log (dose)

• Y-intercept = fa/fu

• X-intercept = log Dm

According to Chou T-C and Talalay P (1984), Y = mX + C is generated. What is the median effect dose?

• C

• -C/m

• antilog C

• antilog (-C/m)

A and B are tested on Vero cells by XTT. Median effect doses of A and B are 5 uM and 50 uM, respectively. Therefore,

• A is more toxic to Vero cells than B.

• B is more toxic to Vero cells than A.