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Choosing the Appropriate Solvent for Solid Materials Tested in the Bovine Corneal Opacity and Permeability (BCOP) In Vitro Assay
In compliance with OECD Test Guideline 437 for eye irritation (BCOP assay), non-surfactant solid materials are typically tested as 20% dilutions prepared in 0.9% sodium chloride solution, distilled water, or other solvent that has been demonstrated to have no adverse effects on the test system. However, the limited solubility of some chemicals adds technical challenges in finding a vehicle that would ensure the material’s availability to the excised corneas and that itself would not affect the test system. In this study, we evaluated five solvents frequently used in the BCOP assay: distilled water, mineral oil, corn oil, polyethylene glycol (PEG)-400, and methocel solution (0.5%). Based on the available classification systems, our preliminary data showed that water, methocel, mineral oil and corn oil were predicted as non-irritants, while PEG-400 was predicted as a mild irritant. To demonstrate the influence of the type of solvent on the outcome/prediction of the BCOP assay for solid materials, we tested a 20% suspension of benzoic acid (BA) prepared in these solvents. BA has a non-polar benzoic ring that would preferably dissolve in non-polar solvents and a polar acidic group with affinity for polar solvents, thus making it a good model for testing its effect on corneas when dissolved in various solvents. Previous animal tests reported moderate to severe eye irritation induced by BA. Our results demonstrated that when mixed in water, mineral oil, corn oil, or methocel, BA was predicted to be a corrosive/severe irritant, while it was predicted to be a moderate irritant when mixed in PEG-400. These results support the need for further investigation of the solvent’s influence in the BCOP assay to allow the correct prediction of the irritation potential of solid materials.
Application of the KeratinoSens Assay for Prediction of Dermal Sensitization Hazard for Botanical Cosmetic Ingredients
An essential step in the safety review of cosmetic/personal care ingredients is hazard assessment for a series of endpoints, including dermal sensitization potential. In vitro methods have been developed to identify allergic (haptenic) potential for individual chemicals based on electrophilic interaction with marker peptides or cellular target systems. These assays generally use a specific molar ratio of the test chemical to the test system. Botanical extracts are used increasingly in formulas and, as mixtures, specific molar ratios cannot be determined for these assays. Often, the botanical extract portion is a relatively small portion of the complete ingredient. To assess these mixtures, the KeratinoSens assay was selected because it operates over a wide dose range and sets cytotoxicity limits on doses used to measure marker gene expression (Emter et al, 2010 ). In the KeratinoSens assay, the induction of a luciferase gene, under the control of the antioxidant response element (ARE) derived from the human gene AKR1C2 gene, is measured. In parallel, cytotoxicity is assessed by both Neutral Red Uptake (NRU) and MTT assays. Test concentrations ranged up to 1000 μg/mL (of complete ingredient) and a test concentration was considered positive if the relative viability was ≥ 70% and the fold induction of luciferase was 1.5x relative to the solvent controls. The goal of the study was to measure the activity of 3 known sensitizers (gluteraldehyde (GA) [strong], dimethyl maleate (DM) [moderate] and cinnamic aldehyde (CA) [moderate] spiked into four different botanical ingredients (each with a different excipient solvent systems). The “spiked” botanical ingredients were used as the test article as no sensitizing botanical ingredient was available. Activity of the spiked sample was measured relative to the EC1.5 of the neat sensitizer as a function of sensitizer concentration and extract composition. Three independent trials were performed on each test material. No appreciable cytotoxicity was observed with any of the samples. The recovery of the GA spike required at least a ~3 fold increase in concentration relative to the chemical alone and botanical ingredient #3 reduced the activity below detection. The DM and CA showed activity at about the same effective concentrations as the neat chemical although the DM showed reduced activity in botanical ingredient #3 as well. These data suggest that the KeratinoSens assay has the potential to identify electrophile allergens within a botanical ingredient matrix.
The Bovine Corneal opacity and Permeability (BCOP) assay can be used for predicting mild, moderate, and severe ocular irritation through quantitative assessment of the changes in opacity and permeability of the bovine cornea. In addition, histological evaluation of the corneas can be performed to assess the depth of damage. The BCOP assay with histology was used to determine the ocular irritation potential of prototype cleaning products with antimicrobial claims according to the guidance provided by the EPA-Office of Pesticide Program (OPP). Several prototype cleaners with similar formulation were evaluated along with a reference material. The results of the BCOP assay showed noticeable differences among the products. The in vitro score, determined by changes in opacity and permeability, of the corneas treated with products ranged from ~15 to 80. These scores indicate mild, moderate, and severe irritation according to the guideline provided in the EPAOPP document. In addition, the histological evaluation of the corneas showed differences in the depth of damage between moderate and severe category products, confirming the in vitro score.
The assay distinguished ocular irritation potential among similar prototypes demonstrating its effectiveness during product development. Additionally, the results demonstrate the utility of the BCOP assay with histology as a stand-alone assay for eye irritancy evaluation in the EPAOPP program.
Screening of Cosmetics Ingredients for Phototoxic Potential Using the In Vitro 3T3 Neutral Red Uptake Phototoxicity Test
Phototoxicity is an acute toxic response after exposure to a phototoxicant and either UV radiation or visible light (UV/VIS). Phototoxicity from substances applied topically typically occurs at the site of photo-irradiation. Phototoxicity is the result of direct cellular damage caused by a non-immunological inflammatory response. Clinically, phototoxicity resembles an exaggerated sunburn (erythema, increased skin temperature, pruritis and edema). Phototoxicity reactions have been reported for both synthetic substances and those which occur naturally (e.g., botanical extracts). Although symptoms generally subside quickly, the potential for substances used in topical products to cause phototoxicity is clearly of concern for manufacturers of cosmetics, personal care and other consumer products. Historically, the potential to cause phototoxicity from substances applied topically was evaluated by utilizing various animal models. However in 1997 the 3T3 Neutral Red Uptake Phototoxicity Test (3T3 NRU PT) was validated by ECVAM’s Scientific Advisory Committee as an in vitro method for evaluating the phototoxic potential of chemicals shown to absorb in the UV/VIS range. To illustrate the utility of the 3T3 NRU PT as a useful screening tool in the safety evaluation of potential cosmetic ingredients, the results of the evaluation of 42 botanical extracts and 25 synthetic chemicals found to absorb in the UV/VIS range are reported. Most substances evaluated were found not to be phototoxic in vitro; however, 9 substances were identified as potentially/probably phototoxic in the 3T3 NRU PT and were eliminated from further consideration for use as cosmetic ingredients. Several substances found to be non-phototoxic in the 3T3 NRU PT were formulated with other ingredients in a prototype cosmetic formulation and subject to clinical testing. No manifestations of phototoxicity were observed in any of the test subjects in the prototype formulation containing any of the substances identified as non-phototoxic in vitro.
Surfactant Responses in the Bovine Corneal Opacity and Permeability Assay: Points to Consider for In Vitro Eye Irritation Testing
The Bovine Corneal Opacity and Permeability (BCOP) assay is an ex vivo test used to evaluate the ocular irritation of a broad range of chemicals. In the regulatory classification and labeling arena, BCOP can be used to identify severe and corrosive eye irritants according to the OECD Test Guideline (TG) 437. However, BCOP has historically under-predicted certain anionic surfactants, when tested according to the standard liquid protocol. TG 437 specifies that liquid surfactants may be tested as 10% aqueous dilutions for 10 minutes (although alternate dilutions and exposure times may be conducted with scientific rationale), and the relevant guidance document (GD) No. 160 suggests that solid and concentrated liquid surfactants may be diluted to 10% for testing. However, GD No. 160 further directs that surfactant-based formulations are usually tested neat, but could be diluted with justification, imparting some confusion in identifying the most appropriate test methods. Since neither the basis for selecting the appropriate surfactant test methods, nor the justification for modifications are clearly presented in TG 437 or GD No. 160, we present on the testing of sodium lauryl sulfate (SLS) in the BCOP assay, using standard and modified dilutions and exposures, to elucidate the impact of these variables on eye irritation prediction. For example, in vitro scores of 20.7, 28.4, and 28.3 were obtained when testing SLS at concentrations of 50, 20, and 10% for 10 minutes, showing that irritation responses were not fully concentrationdependent, but demonstrated optimally at intermediate doses. When tested using modified exposure times, SLS showed time-related responses, with improvements in irritation predictions at the 20 and 30 minute exposures. Histopathology was performed to assess the surfactant-induced corneal changes. Based upon these results, a framework for testing surfactants, and surfactant-based formulations is proposed.
The inter-laboratory reproducibility of the STE test for assessing eye irritation of cosmetic products
STE test is an in vitro eye irritation test using cell viability as an end point in SIRC cells following just a 5 minute treatment, and the good correspondence has been confirmed between the STE irritation categories (non irritant [NI] and irritant [I]) and GHS categories (NC and category 1 [Cat. 1]/category 2 [Cat. 2]). Generally, cytotoxicity tests using cultured cells have an advantage of being simple, a quick procedure, and a low evaluation cost. The STE test has the advantages not only easy-to-use but also evaluable the eye irritation potential of water insoluble substances by using mineral oil as test vehicle. The STE test is planned for peer review in 2013 and may be accepted as an OECD test guideline for classifying ocular irritation. In this study, the technical transferability and inter-laboratory reproducibility of the STE test were evaluated in 3 contract research laboratories as a naive laboratory.
Validation of In Vitro and Clinical Safety Assessment of Leave-On Body Lotions Using Post-Marketing Adverse Event Data
Behentrimonium chloride (BTC) is a straight-chain alkyltrimonium chloride compound commonly used as an antistatic, hair conditioning, emulsifier, or preservative agent in personal care products. Although the European Union restricted the use of alkyltrimonium chlorides and bromides as preservatives to ≤0.1%, these compounds have been safely used at ≤5% in hundreds of cosmetic products for other uses than as a preservative. In vitro, clinical, and controlled consumer usage tests in barrier-impaired individuals were conducted to determine if whole body, leave-on skin care products containing 1-5% BTC cause dermal irritation or any other skin reaction with use. BTC-containing formulations were predicted to be non-irritants by the EpiDerm®* skin irritation test and the bovine corneal opacity and permeability (BCOP)/chorioallantoic membrane vascular assay (CAMVA) ocular irritation test battery. No evidence of allergic contact dermatitis or cumulative dermal irritation was noted under the exaggerated conditions of confirmatory human occlusive patch tests. No clinically assessed or self-reported adverse reactions were noted in adults or children with atopic, eczematous, and/or xerotic skin during two-week and four-week monitored home usage studies. These results were validated by post-marketing data for five body lotions, which showed only 0.69 undesirable effects (skin irritation) reported per million shipped consumer units during 2006-2011. No serious undesirable effects were reported during in-market use of the products. Therefore, if formulated in appropriate conditions at 1-5%, BTC will not likely cause dermal irritation or delayed contact sensitization when used in a whole-body, leave-on product.
Using Novel In Vitro NociOcular Assay Based on TRPV1 Channel Activation for Prediction of Eye Sting Potential of Baby Shampoos
The transient receptor potential vanilloid type 1 (TRPV1) channel is one of the most well-characterized pain-inducing receptors. The purpose of this study was to predict human eye stinging of 19 baby bath and shampoo formulations by studying TRPV1 activity, as measured by increase in intracellular free Ca2+. The NociOcular test, a novel recombinant neuronal in vitro model with high expression of functional TRPV1 channels, was used to test formulations containing a variety of surfactants, preservatives, and fragrances. TRPV1-specific Ca2+ influx was abolished when the TRPV1 channel antagonist capsazepine was applied to the cells prior to shampoo samples. The positive control, an adult shampoo that contains cocamide monoethanolamine (CMEA), a known stinging ingredient, was the most active sample tested in the NociOcular test. The negative control, a marketed baby shampoo, was negative in the NociOcular and human tests. Seven of the formulations induced stinging in the human test, and of those six were positive in the NociOcular test. Twelve formulations were classified as nonstinging in the human test, and of those ten were negative in the NociOcular test. There was no correlation between the clinical stinging results for the baby formulations and the data generated from other in vitro eye irritation assays (cytosensor microphysiometer, neutral red uptake, EpiOcular, transepithelial permeability). Our data support that the TRPV1 channel is a principal mediator of eye-stinging sensation induced by baby bath and shampoo formulations and that the NociOcular test may be a valuable in vitro tool to predict human eye–stinging sensation.
COLIPA validation of the Reconstructed Human Skin Micronucleus Assay (RSMN): A novel micronucleus assay in a 3D human skin model
Current mammalian cell in vitro genotoxicity assays induce a high level of false positive results leading to a large number of costly and time consuming followup in vivo genotoxicity studies. As of March 2009, the 7th Amendment to the EU Cosmetics Directive prohibits the use of in vivo genotoxicity tests in safety assessments for cosmetics, greatly impacting the assessment of genotoxicity of new ingredients. To address this, the European Cosmetic Toiletry and Perfumery Association (COLIPA) initiated an international project to establish and evaluate more predictive in vitro genotoxicity assays using 3D human tissues. One focus has been on the 3D human skin micronucleus assay (RSMN) in EpiDermTM. Since skin is the first site of contact with maximum exposure to many different products including cosmetics, the RSMN assay offers the potential for a more realistic application/metabolism of test compounds for evaluating genotoxicity (1,2,3). The COLIPA RSMN project is a multi-lab initiative involving Procter & Gamble (US), LOreal (France), Henkel (Germany), and the Institute for In Vitro Sciences (IIVS, US). Intra-laboratory and inter-laboratory reproducibility have been investigated with model genotoxins mitomycin C and vinblastine sulfate as well as a variety of chemicals that require metabolic activation. In addition studies with coded chemicals are in progress. This model is a promising new in vitro method for detecting micronuclei induction in human skin. This work is funded by the European Cosmetic Industry Association COLIPA.
The Utilization of the EpiOcular™ Human Tissue Model to Assess and Compare the Irritation Potential of Multiple Surfactant Systems Used In Shampoos And Facial Cleansers
Assuring the safety of cosmetics and personal care products without testing in animals is a primary goal for Alberto-Culver Company. In addition, the Seventh Amendment to the Cosmetics Directive requires that after 2009, animal testing cannot be used to assess the eye or skin irritation potential of either cosmetic formulations or ingredients. To address these issues, we have developed an in vitro irritation assessment program to support the ocular safety evaluation of multiple surfactant systems used in shampoos and facial cleansers. This is particularly important as eye irritation is a foreseeable occurrence in the use of these cosmetics and personal care products. The program relies on the results of a topical application of formulations to the surface of a three-dimensional, human cell-derived model of the corneal epithelium (EpiOcular™, MatTek Corp., Ashland, MA, USA) and monitoring time to toxicity. 35 finished products and 15 prototype formulations with a range of multiple surfactant systems have been tested at dilutions of 2% and 10% (w/v in water). Two surfactant reference standards with well established safety profiles in commerce were tested along with these materials at same dilutions of 2% and 10%. The irritation potential of materials was then assessed by comparison to these benchmark materials. At these dilutions, we determined that the irritancy potential for most of the prototype shampoos fell in the mild to no irritation range shown as similar and less cytotoxic responses compared to the Reference materials. The effectiveness of this in vitro test system was evaluated by comparing the in vitro test results with consumer experience information.