CeeTox

Phototoxicity

CeeTox has developed screens that offer alternatives to animal testing in support of the European regulations in REACH and Amendment 7 to the Cosmetics Directive.

By using the in vitro dermal phototoxicity testing services CeeTox offers, clients can practice the 3Rs (reduce, refine, or replace animal testing) and achieve Amendment 7 and REACH directives by reducing or eliminating the need for in vivo testing. These in vitro assays produce reliable outcomes that supplement or replace in vivo data at reasonable cost.

The CeeTox internal review and validation process encompasses discovery, scientific review, and method development. We test and optimize methods using small well-defined chemical sets and perform internal validation with a blinded standards set. Additionally, we participate in formal validation studies for new protocols and submit our novel protocols to validation authorities.

Phototoxicity tests are used to identify the phototoxic potential of a test substance induced by the excited chemical after exposure to light. The test evaluates photo-cytotoxicity by the relative reduction in viability of cells exposed to the chemical in the presence versus absence of light. Substances identified by this test are likely to be phototoxic following systemic application and distribution to the skin, or after topical application.

CeeTox offers two in vitro models for use as phototoxicity screens. For the testing of individual ingredients where solubility is acceptable, the BALB/c 3T3 mouse fibroblast cell line can be used as the test system.

In situations where compound solubility may limit the use of the above model, or where confirmation of a positive finding of phototoxicity is needed, a 3D human skin model will be used.

The in vitro 3T3 NRU phototoxicity test is used to identify the phototoxic potential of a test substance induced by the excited chemical after exposure to light. The test evaluates photo-cytotoxicity by the relative reduction in viability of cells exposed to the chemical in the presence versus absence of light. Substances identified by this test are likely to be phototoxic in vivo, following systemic application and distribution to the skin, or after topical application.

While the 3T3 NRU test is often the only test required if it shows negative phototoxicity of a test article, it might be used as the first step in a tiered phototoxicity testing strategy if it shows the compound to be positive.

Tests have revealed that substances which are known to be safe in humans, and yet have yielded positive results in the 3T3 NRU assay, exhibit their true negative phototoxic potential when topically applied to the Reconstructed Skin Model at low concentrations, such as found in a formulation. This is due to the well-developed barrier of the 3D model, which prevents the chemicals from penetrating into the deeper parts of the epidermis and subsequently causing damage to the cells.

Viability of both irradiated and non-irradiated tissues will be determined using the recommended MTT assay. Histological examination will be performed as an additional endpoint on the remaining tissues.

CeeTox has a number of phototoxicity assays for you to choose from:

3T3 NRU Phototoxicity Test (in vitro)

The phototoxicity test is used to identify the phototoxic potential of a test substance induced by the excited chemical after exposure to light. The test evaluates photo-cytotoxicity by the relative reduction in viability of cells exposed to the chemical in the presence versus absence of light.

Substances identified by this test are likely to be phototoxic following systemic application and distribution to the skin, or after topical application.

Phototoxicity Test (in vitro) – 3D Cell Model

Let CeeTox scientists become an extension of your R&D team when we put our experience to work for you interpreting the data that enables you to make the best decisions and bring safer products to market faster and at lower cost.

Literature Cited

http://www.alttox.org/ttrc/toxicity-tests/skin-irritation/way-forward/hayden/

OECD Guideline 432 for Testing of Chemicals, In vitro 3T3 NRU phototoxicity test, 2004.

MatTek Corp., ECVAM Feasibility Study: Can the pre-validated in vitro skin model phototoxicity assay be upgraded to quantify phototoxic potency of topical phototoxin? Kandarova, H. et. al., 2005.