ATP quantification is a widely accepted method for assessing viability because healthy cells contain closely regulated levels of the biomarker [30, 31] . Non-viable cells not only lose the ability to synthesize ATP, but also contain en- dogenous ATPases that rapidly deplete the existing ATP. Luciferase reaction chemistry is used to quantify ATP, the limiting reactant, by generation of a luminescent signal that is proportional to viable cell number [32, 33] .