Potential eye irritation of some “biodegradable” liquid scintillation cocktails determined in vitro

The potential eye irritation of a range of liquid scintillation cocktails has been evaluated by an in vitro method using the chorioallantoic membrane as an alternative to the Draize rabbit test. All the cocktails studied are potentially moderately to strongly irritant. The only slightly irritant product was Solventgreen, which is a solvent used in some of the cocktails. There is a correlation between the concentration of the cocktail and the potential eye irritation induced. Manufacturers of chemicals including liquid scintillation cocktails should accept responsibility for disclosing data about the composition and toxicity of their products with regard to waste disposal and safety of laboratory staff.

Assessment of primary eye and skin irritants by in vitro cytotoxicity and phototoxicity models: an in vitro approach of new arginine-based surfactant-induced irritation

Extensive efforts have been made, recently, to find surfactants with lower irritation potential than those presently commercially available, for use in pharmaceutical and cosmetic preparations. Cytotoxic and phototoxic effects of a novel family of dicationic arginine-diglyceride surfactant compounds, 1,2-diacyl,3-O-(l-arginyl)-rac-glycerol with alkyl chain lengths in the range from 8 to 14 carbon atoms, were compared to three commercial surfactants. The end-points used to assess toxicity were the red blood cell lysis assay and uptake of the vital dye neutral red 24h after dosing (NRU), respectively. Two immortalized cell lines, murine fibroblast cell line, 3T3, and one human keratinocyte cell line, HaCaT, were used as in vitro models to predict the potential phototoxicity which could result in irritation, determined by resazurin reduction to resorufin and neutral red uptake (NRU). All tested surfactants had cytotoxicity effects as demonstrated by and decrease of NR uptake, which showed a clear concentration-response relationship. Concentrations resulting in 50% inhibition of NR uptake (IC(50)) range from 1 microM(-1) (hexadecyl trimethyl ammonium bromide) to 565 microM(-1) (12,12-l-arginine). Erythrocyte haemolysis also showed a clear concentration-response relationship, the 50% of haemolysis ranged from 37 microM(-1) (10,10-l-arginine) to 151 microM(-1) (sodium lauryl sulphate). Phototoxicity was performed with 12,12-l-acetyl-arginine, the most stable chemical structure. The validated 3T3 NRU photoxicity assay was used and revealed a phototoxic potential.

A collaborative evaluation of the cytotoxicity of two surfactants by using the human corneal epithelial cell line and the WST-1 test

This study was undertaken to investigate the use of the in vitro test WST-1, an assay of cell proliferation and viability, for a preliminary safety evaluation of topical ophthalmic preparations. The cytotoxicity of two surfactants, benzalkonium chloride (BAC) and polyoxyethylene-20-stearyl ether (Brij78, PSE) was independently investigated in four laboratories in the EU by using an immortalized human corneal epithelial (HCE) cell line. The HCE cells were exposed to BAC and PSE for 5 min, 15 min, and 1 hour, and the results of the HCE-WST-1 tests were collected and compared. After one-hour exposure, the EC(50) values in BAC-treated cells in the presence of serum ranged between 0.0650 +/- 0.0284 (mean +/- SD) mM, and those in the absence of serum 0.0296 +/- 0.0081 mM. The corresponding values for PSE were 0.0581 +/-.0300 mM and 0.0228 +/-.0063 mM. There were variations in the results between different laboratories, with coefficients of variation ranging from 31 to 121%, mean 58%. The use of one-hour exposure time is to be preferred, and the elimination of serum in the culture medium is recommended to avoid both underestimation of toxic effects and variability of the test results.

Ocular tolerance of preservatives on the murine cornea

We investigated the effects of instilling 13 commonly used preservatives on the murine cornea in vivo. Due to the instillation of preservatives, micro-lesions are formed on the cornea and can be selectively marked by fluorescein. The sum of the resulting fluorescent areas was measured using an episcopic microscope coupled to an image processing system. All the tested preservatives proved to be well-tolerated by the eye at commonly used concentrations. However, in some cases, increased concentrations of preservatives or combinations resulted in significant increase of the amount of corneal damage. With increasing the concentration, corneal lesion increased the most in the case of cetylpyridinium. While a combination of chlorobutanol 0.5% and phenylethylalcohol 0.5% did not result in an increase in corneal damage (when compared to the use of each separately), the associations of thiomersal 0.02% and phenylethylalcohol 0.4% on one hand and of edetate disodium (EDTA) 0.1% and benzalkonium 0.01% on the other, resulted in significant increases in the amount of corneal damage. However, in none of the tested combinations, the increase in the observed damage exceed the limit of ocular intolerance we had defined beforehand: thus, they were all deemed relatively well-tolerated. In the last part of the study, we investigated the effects of combining several preservatives, at usual concentrations, with an anesthetic solution of oxybuprocaine and found no notable increase in ocular damage.

Cytotoxicity potential of surfactant mixtures evaluated by primary cultures of rabbit corneal epithelial cells

The use of in vitro cytotoxicity assays as potential alternatives in assessing ocular irritation of surfactant mixtures was evaluated in a primary culture system of rabbit corneal epithelial cells. Two groups of surfactant mixtures, each with the same surfactant components in varying proportions, were studied. Cytotoxicity was determined by lactate dehydrogenase (LDH) enzyme leakage and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) dye reduction in the cell culture system. There was a good correlation between the cytotoxicity in vitro and the reported Draize eye irritation data within each group of the surfactant mixtures studied.

Evaluation of surfactant cytotoxicity potential by primary cultures of ocular tissues: I. Characterization of rabbit corneal epithelial cells and initial injury and delayed toxicity studies

This investigation was undertaken to develop cytotoxicity assay systems using primary cultures of rabbit corneal epithelial cells as an experimental model to evaluate oculotoxic agents and the ability of these in vitro assay systems to predict irritancy potential and delayed toxicity. We have characterized the epithelial nature of the cultures by identifying keratins with antikeratin antibodies (AE1/AE3) and by demonstrating metabolic enzymes important to the integrity of the cells: lactate dehydrogenase, glucose 6-phosphate dehydrogenase and aldolase. Eight surfactants were compared and ranked according to their cytotoxic potential. We evaluated cytotoxicity by measuring leakage of the cytosolic enzyme, lactate dehydrogenase, into the medium, by making morphological observations and by assessing lysosomal neutral red uptake and mitochondrial 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction. The cells were treated for 1 h with the surfactants and the possibility of delayed toxicity was evaluated 24 h after removal of the surfactant. The cytotoxicity of the different types of surfactants as shown by all the tests was cationic > anionic = amphoteric > non-ionic. Triton X-100, a non-ionic surfactant but a severe irritant, had a ranking similar to anionic surfactants. The in vitro rankings corresponded well to reported in vivo Draize rabbit eye test data. The 24-h test for lactate dehydrogenase leakage showed that mild and non-irritating surfactants did not demonstrate any subsequent damage after a 1-h exposure, but the extreme and severe surfactants continued to show further damage after the 1-h exposure. These in vitro findings were similar to reported in vivo results. The neutral red and MTT tests did not adequately predict the prolonged toxicity of the more irritating surfactants, as was demonstrated by the lactate dehydrogenase leakage test. We conclude that in vitro cytotoxicity assays using primary cultures of rabbit corneal epithelial cells may be used to rank the cytotoxic potential of surfactants, but only the lactate dehydrogenase leakage test was able to assess prolonged cell injury.