Phototoxicity Testing

Scientists at our Horsham site pioneered the quantitative study of cutaneous phototoxicology by designing the instruments, techniques, and protocols now accepted as industry standards for regulatory phototoxicity evaluations. We have used this strong foundation to develop unique and technologically rigorous in vivo phototoxicity testing services in collaboration with our research models’ experts and highly skilled pathologists to support our clients’ research.

We perform phototoxicology assays in mice, rats, and guinea pigs, as well as photo allergy studies in guinea pigs. We also offer safety assessment studies to evaluate both photodynamic drugs and unique light sources. Dosing routes include oral, intravenous, dermal, intraocular, and ocular instillation, both single and multiple administrations.

We can assess the effects of exposure to visible light and ultraviolet radiation on ocular structures. Our study designs can include acute, continuous, or interrupted light exposure, and we can perform slit lamp biomicroscopy, indirect ophthalmoscope, and tonometry. Our staff includes board-certified veterinary ophthalmologists and pathologists skilled in evaluating light-induced ophthalmic pathology.

Our team can perform assessments of light exposure under surgical conditions using UVR, visible or near-infrared sources as well evaluate as the potential damage to thoracic and abdominal organs in rodents.

We can perform in vitro photosafety evaluations, primarily the OECD 432/ICH S10-compliant in vitro 3T3 neutral red uptake phototoxicity testing. Along with the in vitro 3T3 NRU phototoxicity test, we can perform the in vitro assessment of phototoxicity using 3D epidermal cell systems, the photomutagenicity assay, and the melanin binding assay. We will customize phototoxicity assays to undertake screening for large numbers of compounds for compound selection during development along with performing GLP-compliant assays.

Phototoxicity is a type of adverse reaction that can occur when the skin, eyes, or other exposed tissues are exposed to both a phototoxic substance and ultraviolet (UV) light. This can happen when the phototoxic substance absorbs the UV light and undergoes a chemical change that produces harmful molecules, such as free radicals. These molecules can damage cells, leading to a variety of symptoms, including redness, swelling, itching, burning, and blisters.

Phototoxicity testing is a laboratory test that assesses the potential of a chemical to cause skin damage after exposure to UV light. It is typically performed on new drugs and cosmetics before they are marketed to consumers, but it can also be used to evaluate the phototoxicity potential of other chemicals, such as pesticides, herbicides, and industrial chemicals.

There are two main types of phototoxicity testing: in vitro and in vivo. In vitro testing is performed on cells or tissues in a laboratory setting, while in vivo phototoxicity testing is performed on animals.

Phototoxicity testing is an important tool for assessing the safety of chemicals before they are marketed to consumers. By identifying chemicals that have the potential to cause phototoxicity, manufacturers can take steps to reduce the risk of consumers experiencing adverse reactions.

The 3T3 Neutral Red Uptake Phototoxicity Test, commonly referred to as the 3T3 NRU phototoxicity test, is a standardized in vitro (in the laboratory) test used to assess the potential phototoxicity of chemicals, pharmaceuticals, and cosmetic ingredients. This test is a part of the safety evaluation process for these substances, helping to identify compounds that may cause adverse reactions when exposed to light.

Here's how the in vitro 3T3 NRU phototoxicity test test is typically conducted:

Cell Line: The test uses 3T3 mouse fibroblast cells, which are a type of connective tissue cells. These cells are exposed to the substance being tested

Exposure to Light: After exposure to the test substance, the cells are exposed to ultraviolet (UV) or visible light. This light exposure simulates sunlight or artificial light sources that could trigger phototoxic reactions.

Assessment of Cell Viability: The viability of the exposed cells is then assessed by measuring the uptake of a dye called neutral red. This dye is incorporated by living cells, and the amount of dye uptake is an indicator of cell viability. If a substance is phototoxic, it may cause damage to the cells, reducing their ability to take up the dye.

Calculation of Phototoxicity Potential: The reduction in neutral red uptake is quantified, and a comparison is made between cells exposed to the test substance plus light and cells exposed to the test substance alone. The degree of reduction in cell viability in the presence of light is an indication of the substance's potential to cause phototoxicity.

The in vitro 3T3 NRU phototoxicity test is a relatively simple and inexpensive test to perform, and it is reproducible and reliable. It is a valuable tool for assessing the phototoxicity potential of chemicals, widely used in industry and academia, and an important part of the safety assessment of new products.