Each of the analysed substances must be subjected to a pilot study, which is conducted in order to determine whether it is distinguishable using the Raman technique from other components of the final product.
The pilot study is also conducted in order to determine whether the test substance has intense, characteristic bands for skin permeation testing. After the pilot study, a decision is made to conduct the next steps of the analysis (tracking the permeation of the selected active substance).
Test conducted after a positive result of the pilot study. The selected active substances are mapped using Raman spectroscopy. On the basis of previously obtained patterns of the active substance under investigation, so-called marker bands are indicated. The depth of penetration of the substance through the skin layers is determined on the recorded maps. The test is performed in 3 repetitions
biological and 3 technical repetitions (statistical confirmation of the depth of penetration).
The test report includes a comparison of the Raman spectrum of the selected active ingredient with the spectrum of the sample (pilot test result). Based on the results, so-called
characteristic spectra are selected, which allow to distinguish active substances during the analysis of the final product. Furthermore, so-called Raman maps (2D) are included in the report, on which the tested active ingredient is marked. Based on the disappearance of the signal from the active substance, the depth of penetration of the respective ingredient into the skin layers is estimated.
Benefits of in vitro skin penetration testing:
- Penetration of a substance into the skin is carried out to check whether a cosmetic formulation overcomes the epidermal barrier.
- The test produces a numerical value representing the depth of penetration into the skin.
- The test is used to compare several formulations with the same active ingredient, in order to select the formulation that allows the best penetration through the epidermis.
- Maps (substance marker bands) obtained in the tests are an excellent supplement to marketing materials
- Possibility to compare a given formulation (recipe) against the competition
- Possibility to select the best, most effective active substance