Regina Bruggisser
= Regina Bruggisser
{c}
\b[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.<Interference of plant extracts, phytoestrogens and antioxidants with the MTT tetrazolium assay by Regina Bruggisser and others>[2002, byline and Abstract, comparison with crystal violet staining]{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.