Transdermal absorption of cosmetics refers to the process by which functional ingredients in cosmetics act on the surface of the skin or enter the epidermis or dermis according to the effectiveness of the product, and accumulate and act in that area. Transdermal absorption test is widely used in the evaluation of transdermal properties and toxicological effects of cosmetic ingredients. CD Formulation can predict the penetration of different cosmetic ingredients in the human body and the possible toxicity of the reaction through in vitro transdermal assay, which can provide a reference basis for the evaluation of the safety of cosmetic products.
The isolated skin of human or animal is mounted on the diffusion cell, the receiving liquid is taken at regular intervals, the content of active ingredients is measured by suitable analytical methods, and the transdermal rate is calculated to evaluate the permeation characteristics of chemicals. The diffusion cell method is easy to operate, saves time and cost, has good reproducibility of results and small variation of limiting parameters, and is applicable to a wide range of isolated skin.
3D skin model is easy to obtain, standardized production, and its structure and physiological metabolism have the consistency with human skin, the use of skin models can also be used to determine the release kinetics of active ingredients in cosmetic formulations, as well as the metabolism of substances after percutaneous absorption.
The choice of transdermal dose and dosage form needs to be determined according to the characteristics of the cosmetic ingredients and the mode of application. Usually, liquid, cream, gel and other dosage forms can be selected, and the concentration and dosage can be controlled.
Transdermal performance parameters include cosmetic transmittance, cumulative transmittance, skin absorption, skin permeability coefficient, etc., which need to be measured by specific testing methods. At the same time, the experimental data need to be statistically analyzed and compared to infer the transdermal performance and safety of cosmetic ingredients.
The in vitro transdermal absorption test is usually divided into the following steps:
(1) Sample preparation: the sample to be tested is prepared into a test liquid or ointment according to a certain ratio.
(2) Transdermal cell culture: Cowhide, piglet skin or other skin models are used to form a transparent transdermal cell model above the transdermal cells, which is used to simulate human skin. At the same time, cell culture and maintenance are required.
(3) Apply agent: Apply the agent to be tested evenly on the transdermal cell model.
(4) Waiting for absorption: According to the requirements of the experimental design, wait for a certain period of time for the agent to be absorbed and metabolized in the transdermal cells.
(5) Sampling and analysis: At different time points, samples are collected from the transdermal cell model using specific methods for analysis and testing.
Compared to animal testing and clinical trials, in vitro transdermal absorption testing has a low cost and does not require the involvement of a large number of laboratory animals or personnel.
In-vitro transdermal absorption testing allows for high-throughput screening and the simultaneous testing of many different cosmetic ingredients and formulations to quickly determine their transdermal properties and toxicological effects.
Since animal testing is subject to ethical and legal constraints, in vitro transdermal absorption testing can be used as an alternative to animal testing to predict the metabolism and toxicological effects of cosmetic ingredients in the human body.