MTT Assay for Cell Viability

MTT assay is an established viability assay [35 ] and was conducted as previously described [36 (link)]. In brief, after respective treatment, MTT reagent (0.5 mg/ml MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid; Sigma-Aldrich, solved in DMEM without phenol red (GE Healthcare, München, Germany)) was applied for 2 hours at 37 °C. DMSO was added to lyse the cells. When measuring SHSY-5Y cells, this protocol was varied [37 ]. Here, MTT supernatants were collected in Eppendorf reaction tubes and centrifuged. Supernatant was discarded and pellets harvested. Pellets were re-administered to their corresponding wells, in which the cells were then lysed with DMSO. After the application of DMSO, in both approaches, the absorbance at λ = 570 nm was measured with a microplate reader (ELx800, BioTek Instruments, Bad Friedrichshall, Germany). Each MTT experiment was independently repeated 3 times.