Comparative assessment of in vitro toxicity of xenobiotics using flow cytometry and spectrophotometry.

Cell viability and cell proliferation are endpoints that can be used to identify cytotoxic effects. In a study of the cytotoxicity of four biomaterials and drugs, these two criteria were determined by different techniques. There were notable similarities and differences among the different methods used. Cell viability, which was determined by the trypan blue exclusion test, spectrophotometric microtitration (neutral red) and flow cytometry (fluorescein diacetate) gave similar results. However, the neutral red assay was found to be the most sensitive method for determining the cytotoxicity of these biomaterials and drugs. Cell proliferation measurement, by cell counts and quantitative protein estimation (coomassie blue), revealed important variations between the two methods and indicated poor sensitivity for the protein assay. A slight variability in the determination of the inhibitory concentration 50 (IC(50)) for the two drugs was observed for all the techniques.