[Evaluation of the cytotoxicity of an antiseptic by a photometric micromethod].

Cytotoxicity of an antiseptic is usually evaluated by microscopic examination of a cell culture, after a set time of contact with the antiseptic. As this evaluation is largely subjective, a photometric method is proposed. The procedure consists in staining the cells by methylene blue after contact with the ATS and measuring the dye in a photometer after elution. Different dilutions of ATS are added to a 24 h-monolayer of Vero cells in a 96-well microtissue culture plate (8 wells for each dilution, 8 wells for cell control, and 8 wells for control of dye fixation by the plastic plate). The plate is incubated for three days at 37 degrees C in an atmosphere of 5% CO2 and 95% air. The plate is washed with PBS to remove dead cells and adherent cells are fixed. The plate is then washed with borate buffer and allowed to dry. The dye is eluted by adding 200 microliter of HCl 0.1 N to each well. The plate is then read automatically at 650 nm on a Titertek Multiskan, a vertical light path photometer. Cytotoxicity is expressed as the percentage of damaged cells as compared to control wells. Cytotoxic assay of glutaraldehyde shows that this technique is more reliable and more sensitive than microscopic examination. Moreover, result of cytotoxic assay and of a method consisting in measurement of protein in residual cells after exposure to ATS are significantly correlated.