 Regina Bruggisser

Regina Bruggisser is first author of a 2002 investigation of chemical interference in the MTT assay. The investigators found that kaempferol could increase formazan production while the independently assessed number of cells decreased.^[ref]

The contribution concerns the interpretation of a measurement: a larger coloured signal need not mean greater cell viability. The MTT assay uses redox conversion of MTT to coloured formazan; if a test substance also drives this reaction, the signal combines cellular and chemical contributions.

An original additive model makes the ambiguity explicit. Let blank-corrected absorbance be $A=qN+I$, where $N$ is viable cell number, $q$ is signal per viable cell and $I$ is chemical interference. Suppose an untreated sample gives $A=0.50$. A treated sample with $qN=0.30$ and $I=0.35$ gives $A=0.65$: apparent signal rises by 30 percent while the cellular contribution falls by 40 percent. These are illustrative values, not measurements from the paper. Measuring a compound-only negative control can test for $I$, but does not establish that $q$ stays constant after treatment.