Tailoring tests from ingredients to products to get you the right data for your requirements.
From the testing of single chemicals or ingredients to mixtures, in vitro testing provides safety information for hazard determination. By looking beyond the currently accepted methods in the OECD test guidelines, ET50 based tests are able to provide potency information for formulations targeted to a diverse range of physiological tissues to make sure the data generated is detailed and relevant for the end use.
When it comes to safety testing of chemicals, the OECD Test Guidelines are recognised internationally as the standards for non-clinical environment and health safety testing of chemicals and chemical products. Section 4 of these Guidelines corresponds to investigating the effects upon health and is the section that contains many of the regulatory test methods that are performed at XCellR8. The Test Guidelines are primarily in used for regulatory safety testing and subsequent chemical and chemical product notification, chemical registration and in chemical evaluation.
The Test Guidelines in Section 4 that we follow at XCellR8 are solely those that do not involve the use of animals and are termed ‘in vitro’ testing. The main focus of these tests is for the classification of mono-constituent chemicals and/or ingredients, and as such in the validation of these test methods, mixtures or multi-constituent substances were not validated.
This, however, does not mean that mixtures or multi-constituent items cannot be tested, but that consideration should be given when determining the meaning of the result at the end. For example, in the case of the skin sensitisation KeratinoSens test, the presence of a high content of non-sensitising cytotoxic constituents may mask the response of weakly sensitising components or sensitising components present at low concentration, but assessment of the mixture can still be performed and useful information regarding the sensitisation potential of the mixture as a whole can be ascertained.
The biggest driver of non-applicability of a test item for the cell-based methods, such as the KeratinoSens method, is not whether the item is a mono-constituent or a mixture, but its solubility in the liquid nutrient-containing medium cells need for survival.
The development of 3D reconstructed tissue models and their incorporation into the OECD test methods has expanded applicability of testing, including mixtures, to resemble both a more human relevant application and negates the limitations imposed by solubility in the 2D cell-based assays. Use of these 3D tissue models enables the testing of neat mixtures and formulations without dilution and is representative of real-world skin or eye exposure. Tests that involve these reconstructed models include skin irritation (OECD TG439), skin corrosion (OECD TG431), eye irritation (OECD TG492 and OECD TG42B) and the EpiSensA method which has been newly incorporated into the in vitro skin sensitisation Test Guideline for theKey Event on Keratinocyte activation (OECD TG442D).
The majority of these methods allow a binary hazard prediction which is important for classification and labelling purposes (CLP), however this criterion is not always the most useful for New Product Development, screening for the mildest formulations, or for the generation of marketing data.
This is where XCellR8’s non-regulatory ET50 methods can help. ET50 tests also utilise reconstructed tissue models however instead of reporting a binary irritant or non-irritant result, the output is an ET50 value. This ET50 value is the time taken to reduce tissue viability to 50% of a negative control. The quicker the cells are injured, the more irritant a product is. The generation of this value therefore allows ranking in order of irritancy, or inversely, mildness, allows categorisation into irritancy classifications such as Severe, Moderate, Mild or Minimal / Non-Irritant and can be used to compare items against development or competitor benchmark formulations.
These tests allow real-life application of personal care and cosmetic formulations, where the basic binary classifications of ‘corrosive/irritant/non-irritant’ obtained for the Test Guidelines are far too harsh. The data generated can be used to tweak final formulations to generate the safest products for future human trials, or the market.
XCellR8 offers ET50 tests using both skin and eye tissues but we also routinely use gingival, oral, vaginal and lung tissues to enable ranking and classification of a wide range of products and mixtures. It is important to test on tissue types suitable for the end-use of the product because physiological differences mean that results may not translate from one type to another.
Using the ET50 approach we have tested a wide range of mixtures and formulations relevant to the personal care and cosmetic industries including moisturisers, soaps, sunscreens and baby care, intimate care and oral care products. This supports the ranking of base formulations, generation of marketing data, improvements to formulations and comparison to off-the-shelf products.
To find out more about the testing of mixtures using the Test Guidelines, the use of physiological tissue types for your testing, or using the ET50 tests to provide potency data, get in touch with us today.
Email info@x-cellr8.com
Call +44 (0)1925 607 134.
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