Which viability test is better: MTT or trypan blue?

Each test has its advantages and limitations.

Trypan blue is a dye exclusion assay in which dead cells will take up the negatively charged dye due to their damaged membranes, while live cells exclude it. This is a rapid and simple assay and is good for analyzing membrane integrity. However, with this assay, cells that are still alive but losing their function will not be stained; there also may be counting errors.

MTT is a colorimetric assay in which viable cells reduce MTT into a purple precipitate formazan, which is then solubilized before measuring absorbance. MTT has higher sensitivity but can also overestimate cell viability and cannot be used with compounds such as polyphenols, ascorbic acid, vitamin A, coenzyme A, and DTT, which can interfere with the reduction of MTT to formazan.