The in vitro 3T3 Neutral Red Uptake (NRU) phototoxicity test is used to identify the phototoxic potential of a test chemical activated by exposure to light. The test evaluates photo-cytotoxicity by the relative reduction in viability of cells exposed to the test chemical in the presence versus absence of light.
| Test Model | Balb/c 3T3 cells |
| Replicates | Six per group (preliminary and confirmatory study) |
| Assay controls | Negative control: Aqueous or organic solvents Positive control: Chlorpromazine (CPZ) Eight different test item concentrations |
| Exposure time | 5 J/CM2 for 50 minutes |
| Test item quantity | 1.0 gram |
| End point | The ability of viable cells to incorporate and bind neutral red (NR) in the presence and absence of light |
| Data delivery | IC50 calculation and photo-irritation factor |
| Timeline | 3 – 4 weeks |
