In Chemico skin sensitization assay
Direct Peptide Reactivity Assay test is becoming the gold standard test in cosmetic applications for skin sensitization testing.
The DPRA test is part of the OECD guideline n°442 and is used to determine the sensitizing potential of a substance.
The molecular initiating event (MIE) in skin sensitization is a binding between epidermal proteins and the sensitizing chemical substance. MIE is part of the adverse outcome pathway (AOP) of skin sensitization.
Two peptides used in the DPRA test and solled by sb-PEPTIDE, the Lysine peptide and Cysteine peptide, mimic the binding of skin proteins when exposed to a chemical agent.
DPRA as an alternative to LLNA tests on animals
The DPRA test is a major advance in characterization of sensitizing elements. It is a non-animal approach. Skin sensitization studies are the cause of death of hundreds of thousands of mice worldwide each year. Therefore, DPRA test has become a preferred alternative to animal studies such as mouse local lymph node assay (LLNA). Also, it is a more effective method, as 22% of skin sensitizers are not detected with the LLNA test, and half of the sensitizers are classified in the wrong category.
As a basis for ‘integrated approaches to testing and assessment’ (IATA), the OECD has therefore developed the DPRA test via the adverse outcome pathways (AOP). OECD has thus enabled the DPRA test to become a new element of choice in the animal study of sensitisers, as a harmonised and validated test.
If you are interested in DRPA tests, SB-PEPTIDE proposes to synthetize your Cysteine peptide and Lysine peptides:
1- Cho SA, Jeong YH, Kim JH, Kim S & al. Toxicol Lett;226(1):106 (2014)
Method for detecting the reactivity of chemicals towards peptides as an alternative test method for assessing skin sensitization potential
BACKGROUND: Cosmetics are normally composed of various ingredients. Some cosmetic ingredients can act as chemical haptens reacting toward proteins or peptides of human skin. They can provoke an immunologic reaction, called as skin sensitization. Indeed, this haptenation process is very important step of inducing skin sensitization and evaluating the sensitizing potentials of cosmetic ingredients is very important for consumer safety. Therefore, animal alternative methods focusing on monitoring haptenation potential are undergoing vigorous research. To examine the further usefulness of spectrophotometric methods to monitor reactivity of chemicals toward peptides for cosmetic ingredients.
OBJECTIVE: Evaluating an alternative method for detecting the skin reactivity of chemicals.
METHOD/RESULTS: Forty chemicals (25 sensitizers and 15 non-sensitizers) were reacted with 2 synthetic peptides, e.g., the cysteine peptides (Ac-RFAACAA-COOH) with free thiol group and the lysine peptides (Ac-RFAAKAA-COOH) with free amine group. Unreacted peptides can be detected after incubating with 5,5′-dithiobis-2-nitrobenzoic acid or fluorescamine™ as detection reagents for free thiol and amine group, respectively. Chemicals were categorized as sensitizers when they induced more than 10% depletion of cysteine peptides or more than 30% depletion of lysine peptides.
CONCLUSION: The sensitivity, specificity, and accuracy were 80.0%, 86.7% and 82.5%, respectively. These results demonstrate that spectrophotometric methods can be an easy, fast, and high-throughput screening tools predicting the skin sensitization potential of chemical including cosmetic ingredient.