Cell media were removed and cells were washed twice with 200 µL of PBS buffer per well. CTG and GSH assay reagents were added to the wells and the assays were performed following the protocols of the Promega assay kits. Briefly, to perform the CTG assay, 100 µL of CTG solution was added into each well. The plate was gently shaken and incubated in the dark for 30 min and luminescence was measured using a Perkin Elmer VICTOR X3 plate reader. To perform the GSH assay, luciferin-NT substrate and glutathione S-transferase were mixed into the GSH-GLo solution. 100 µL of the mixed solution was added into each well. The plate was gently shaken and incubated in the dark for at least 30 min. 100 µL of Luciferin Detection Reagent was added per well. The plate was gently shaken and incubated in the dark for at least 15 min. Luminescence was measured using a Perkin Elmer VICTOR X3 plate reader.