¹Department of Materials Science and Engineering, ²Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, Bunkyo 3-9-1, Fukui-Shi 910-8507, Japan.

Abstract: This research shows a novel method for hazard identification of a chemical and UV light on a single cell level with a laser probe beam. The laser probe beam was passed through interface of cell membrane/culture medium of a cultured human hepatoblastoma cell line HepG2. Deflection of the laser probe beam, which was induced by changes in concentration gradients due to the active materials movement across the cell membrane, was monitored. When a toxic hazard existed, a living cell was expected to be killed or injured, or cellular behaviors to be changed greatly. Then, the changing deflection signal from the living cell would become unchanged or altered in a different way. This was successfully demonstrated with cytotoxity of UV light and H2O2. Most of the cultured HepG2 cells showed changing defl ection signals after 10 min illumination of UV-visible light longer than 370 nm, while almost all HepG2 cells showed unchanged deflection signal after 10 min illumination of UV-visible light with wavelength longer than 330 nm. The results suggested that UV light between 330–370 nm could kill the cells. Additions of H₂O₂ solution with different concentrations to the cell cultures caused the changing deflection signal from a living cell either unchanged or changed in different trend, suggesting toxicity of H₂O₂ to the cells. The results from the beam deflection detection agreed well with those obtained by the conventional trypane blue method.