 Willi Schaffner

Willi Schaffner coauthored the 2002 investigation of interference by plant-derived substances and antioxidants in the MTT assay.^[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.^[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.