Figure 1. Determination of viable cell number on the plate. MC3T3-E1 cells were inoculated on coverslips in 24-well plate (I). Coverslips on which the cells were attached were taken by tweezers (II) and transferred to a new 24 well plate and fresh culture medium containing WST-1 solution was added (IV). Aliquots of the culture medium supernatant were transferred to a 96-microwell plate, and the absorbance at 450 nm was determined (A). The principle of WST-1 assay is shown in (B). WST-1 simultaneously detects not only viable cells but also O2–, present in the culture medium. EC represents electron-binding reagent. RS represents mitochondrial succinate-tetrazolium reducing system.