Microplate spectrophotometry for the high-throughput screening of cytotoxic molecules

Objectives: High-throughput chemical and biochemi- cal technologies are now exploited by modern phar- macology and toxicology to synthesize a multitude of new molecules with bioactive potential, or to isolate them from living matter. Testing molecules in cell sys- tems on a large scale, however, is a rate-limiting step in drug discovery or in toxicity assessment. In this study, we developed a low-cost high-throughput method for first-level screening of cytotoxic molecules. Materials and methods: We used microplate spectro- photometry to measure growth kinetics of human tumour cells that grow in suspension (Molt3) or adherent to the plastic surface of culture wells (HeLa) in standard RPMI medium. Cells were trea- ted with colchicin, idarubicin or paclitaxel under var- ious treatment schedules. The effects were quantified and compared with those measured by optical microscopy using the trypan blue dye exclusion method to reveal dead cells. Results: Proliferation kinetics of tumour cells can be quantified by measuring variations in optical densi- ties of cell samples at 410 and 560 nm wavelengths. For cells that grow in suspension, one single reading at 730 nm may be sufficient to reconstruct growth curves that parallel those obtained by direct cell counting. Effects of the cytotoxic treatments could also be quantified and results compared very favour- ably with those obtained using standard techniques. Conclusions: Microplate spectrophotometry is a robust and sensitive method to monitor growth of animal cell populations both in the absence and in the presence of cytotoxic drugs. This method imple- ments existing technologies and can be fully auto- mated.