In vitro phototoxicity test 3T3 NRO – OECD 432

Phototoxicity refers to a toxic reaction triggered by the exposure of a chemical substance to light, generally in the UV-A range. This phenomenon is particularly monitored for cosmetic, pharmaceutical, or dermatological products intended for cutaneous or ophthalmic use. The 3T3 NRU OECD guideline ), is a in vitro for assessing this risk without resorting to animal testing.

Purpose of the test

This test aims to determine whether a substance or formulation has phototoxic potential in the presence of UV light. It allows:

• Demonstrate the safety of a cosmetic ingredient or photosensitive excipient
• Complete a cosmetic or REACH regulatory dossier
• Select safe ingredients for products exposed to light (sunscreens, day care, perfumes, etc.)
• Identify cellular effects induced by combined exposure to substance + UV radiation

Principle of the 3T3 NRU method

The test involves exposing murine Balb/c 3T3 fibroblast cells to the test substance, with or without exposure to UV-A radiation. Cell viability is then measured by uptake of neutral red, a dye that accumulates in the lysosomes of living cells.

A significant decrease in cell viability after UV exposure compared to the unirradiated sample is interpreted as a phototoxic response.

Methodology

• Preparation of a range of concentrations of the test product
• Application on 3T3 cells in dual condition: with and without UV
• Dose-controlled UV-A irradiation
• Incubation, then addition of neutral red dye
• Spectrophotometric reading of absorbance
• Calculation of the Phototoxicity Index (PIF) and/or the Photo-Irritation Factor (MPE)

Affected matrices

• Cosmetic products (sun care, creams, gels, lotions)
• Excipients, perfumes, UV filters
• Chemical substances or plant extracts used in formulation
• Topical medications or dermatological products

Why choose YesWeLab?

YesWeLab connects you with laboratories specializing in regulatory and phototoxicity studies, with equipment calibrated for the OECD 432 test. All tests are carried out according to good laboratory practices (GLP), with full traceability of results and tailored support.

Our team helps you define relevant concentrations, interpret the results and integrate them into your safety dossiers (CPSR) or REACH/BPR registration dossiers.

See also:

• In vitro eye irritation test – OECD 492
• Skin corrosion – OECD 431
• Micronucleus Test – OECD 487