= Willi Schaffner
{c}
\b[Willi Schaffner] coauthored the 2002 investigation of interference by plant-derived substances and <antioxidants> in the <MTT assay>.<Interference of plant extracts, phytoestrogens and antioxidants with the MTT tetrazolium assay by Regina Bruggisser and others>[2002, byline and Abstract]{ref} The work illustrates why a biochemical test must distinguish its intended biological response from reactions of the test substance with its reagents.
The authors observed direct <redox> conversion of the dye with compounds including <resveratrol> in the absence of <cells>.<Interference of plant extracts, phytoestrogens and antioxidants with the MTT tetrazolium assay by Regina Bruggisser and others>[Abstract, cell-free experiments]{ref} Such a result establishes an alternative route to the assay signal; it does not establish whether the compound protects or harms a living <cell>.
An original concentration model shows why a smooth response curve is insufficient evidence of <cell proliferation>. Suppose the cellular contribution to <absorbance> stays fixed at $0.40$, while chemical interference adds $0.10x$, where $x$ is a dimensionless multiple of a chosen test <concentration>. At $x=0,1,2$, measured <absorbance> is $0.40,0.50,0.60$. This perfectly ordered trend contains no increase in viable <cell> number. A matching compound-only series tests the chemical explanation directly; a biological interpretation requires additional evidence.
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