Surfactant cytotoxicity assay based on a silicon transducer

A cytotoxicity assay for surfactants was developed using a potentiometric silicon transducer and Lactobacillus plantarum (NBRC3070), and the results are reported here. L. plantarum was used as the test microorganism for assaying the cytotoxicity of the surfactants. The extracellular pH change resulting from the metabolic pathway was measured by a light-addressable potentiometric sensor. This potentiometric sensor system measured the acidification of the L. plantarum medium; acidification resulting from metabolic activity was inhibited by the toxic activity of the surfactant. Results indicated that the anionic surfactant did not exhibit inhibitory activity in either cell growth or extracellular acidification until 0.2 mM. By contrast, the inhibition activity of cationic surfactants toward cellular growth and metabolic activity was greater than that of anionic surfactants. These results are consistent with those from the growth inhibition assay.