The cell number in each well was determined based on total protein content of the cells using the fluorescamine assay method. Cell number was calculated based on a standard curve depicting the relationship between cell number, protein content and fluorescence (see details in Figure S2 in File S1 ).
For each time point, L15/ex medium was removed from wells, and cells were rinsed with 500 μl of PBS (Dulbecco's Phosphate Buffered Saline w/o calcium and magnesium). Then PBS was replaced by 500 μl of nanopure water, and the well plate was stored at −80°C for at least one hour to disrupt cells. After thawing, 1 ml of PBS and then 0.5 ml of fluorescamine (Sigma-Aldrich, Buchs, Switzerland) diluted in acetone (3 mg of fluorescamine per 10 ml of acetone), was added to each well containing cells and to one additional, cell free, well per plate as a control. Then, each plate was covered with aluminum foil and shaken for 5 minutes. The fluorescence was measured in each well using the Infinite M200 microplate reader (TECAN, Männedorf, Switzerland; excitation: 360 nm, emission: 460 nm).
For each time point, L15/ex medium was removed from wells, and cells were rinsed with 500 μl of PBS (Dulbecco's Phosphate Buffered Saline w/o calcium and magnesium). Then PBS was replaced by 500 μl of nanopure water, and the well plate was stored at −80°C for at least one hour to disrupt cells. After thawing, 1 ml of PBS and then 0.5 ml of fluorescamine (Sigma-Aldrich, Buchs, Switzerland) diluted in acetone (3 mg of fluorescamine per 10 ml of acetone), was added to each well containing cells and to one additional, cell free, well per plate as a control. Then, each plate was covered with aluminum foil and shaken for 5 minutes. The fluorescence was measured in each well using the Infinite M200 microplate reader (TECAN, Männedorf, Switzerland; excitation: 360 nm, emission: 460 nm).