Purpose:
Cytotoxicity of benzalkonium chloride (BAK) is a key factor for eye drop toxicity. This study aimed to determine critical concentration of BAK for cultured ocular surface cells.
Methods:
We evaluated the cytotoxicity of BAK in SIRC (rabbit corneal epithelium origin), BCE C/D-1b (bovine corneal epithelium origin), RC-1 (rabbit corneal epithelium origin), and Chang (human conjunctival cells origin). The viability of cell cultures was determined following the exposure of cells to 11 concentrations (0.0003% to 0.02%) of BAK for 10, 30 or 60 minutes and at undiluted, 2-fold, and 10-fold dilution using the MTT and neutral red assays. The cell viability score (CVS) was used to compare the toxicity of test solutions. The CVS50 was determined by the number of measurements for viability ≥ 50% of control. The CVS40/80 was calculated as follows: CVS40/80 = (number of measurements for viability value >80%) - (number of measurements for viability value <40%).Total of measurements was 72 (3 concentrations, 3 exposure times, 4 cell lines, 2 assays). Results were expressed as % of total measurements (%CVS).
Results:
%CVS50 and %CVS40/80 of each concentration were 0.02%BAK(26, -46), 0.015%BAK(39, -33),0.01%BAK(53, -15), 0.0075%BAK(63, -1), 0.005%BAK(79, 39), 0.003%BAK(96, 72), 0.002%BAK(96, 83), 0.001%BAK(100, 85), 0.00075%BAK(100, 94), 0.0005%BAK(100, 99), and 0.0003%BAK(100, 99). Both %CVSs indicated marked increase of the value around 0.003% and 0.002%BAK, becoming close to 100%.
Conclusions:
Cytotoxicity of BAK to cultured ocular cell lines was very low below the concentration of 0.002%.
Keywords: cornea: basic science • cornea: epithelium • conjunctiva