CHO-K1 cell number response was measured using ab112120. CHO-K1 cells at 0 to 5,000 cells/well/100 µL were seeded overnight in a black wall/clear bottom 96-well plate. The cells were incubated with 100 µL/well of blue indicator solution for 1 hour at room temperature. The fluorescence intensity was measured at Ex/Em = 405/460 nm. The fluorescence intensity was linear (R2 = 1) to the cell number as indicated. The detection limit was 70 cells/well (n=6).