Konzeption und Entwicklung eines Screeningverfahrens zur Identifizierung von für die Hautmikroflora problematischen Hilfsstoffen in Kosmetika
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Philipps-Universität Marburg
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Abstract
Customers and patients have the justified expectation, that cosmetics and topically applied medical products are harmless to health. The longer a substance remains on the skin, the stronger its influence. This also means, that the ingredients used in the formulations should not have any negative effect on the skin microflora. Although this aspect is still underrepresented, more and more products with various labels promise gentle handling of the skin's microflora are gradually being found on the market.
The aim of this work is to find a test system for identifying excipients that can ultimately have a pathogenic effect on the skin. This includes both disturbances in the balance of skin germs, the development of substances that have a direct damaging effect on the epidermis as well as the comedogenic effect of precipitating cleavage products. By combining and developing different techniques and methods for cultivation, incubation and analysis of the germ-test substance combinations, a general recommendation to avoid certain substances should be possible.
Due to irregularities with Staphylococcus gallinarum and Streptococcus mitis occurred during the tests, these germs were only tested incompletely and can be regarded as of limited relevance. Also, with Propionibacterium acnes and the Malassezia yeasts it was not possible to fully test all substances due to the logistical scope. The HPTLC analysis of all combinations of germs and test substances and the investigation of the interactions between bacteria and yeast fungi also remain open for future experiments.
Basically, the bacteria of the skin microflora seem to play only a subordinate role with regard to the metabolism of topically applied substances. In comparison, there are hardly any interactions with the test substances, and in most cases the growth changes are not relevant. Beside the Malassezia yeasts, some bacterial strains of the skin are in principle able to utilize the sebum, produced by the sebaceous glands, by means of hydrolysis. Thus creating important free fatty acids for the acidic environment and the protective barrier of the skin. In case of overproduction due to the additional splitting of fatty acid esters from cosmetics inflammatory reactions could be triggered or the balance of the skin be disturbed and allow non-resident germs to settle. However, this cannot be confirmed with regard to the combinations of bacteria and substance carried out in the HPTLC analysis. Here, no fission products are recognizable in relevant quantities.
The yeast fungi, on the other hand, show clear influences; they use the test substances as a food source and the formation of comedogenic breakdown products can be detected. The incubation period, the number of cells present and the predominant fungal strain have an influence on the metabolic processes. Due to the wide range of substances used, it can be assumed that the majority of substrate-unspecific lipases are involved; we have not investigated the isolation of individual enzymes.
After comparing the test results with the available literature, fatty acids with chain lengths of more than 12 carbon atoms are obligatory for the growth and reproduction of the fungi. Most of the lipophilic skin care products based on oils or emollients are based on fatty acid esters. Fatty alcohols, fatty acids and their esters are very frequently hydrolyzed by the lipases of the yeast fungi. The resulting long-chain cleavage products solidify at body temperature and can thus close the pores. Due to their high proportion of long-chain fatty acids, almost all plant-based and most synthetic emollients fall into this category and are therefore classified as critical.
Fatty alcohols and fatty acids with chain lengths of more than 12 carbon atoms, their esters, molecules with a steric conformation, as well as fatty ethers and hydrocarbons based on silicones or polymers without ester groups are classified as non-critical. Either no metabolism takes place or the resulting breakdown products do not lead to increased growth or remain liquid at body temperature and therefore have no comedogenic effect.
The degree of saturation of the fatty acid monoesters also influences the metabolic activity; unsaturated fatty acids are used by the yeast fungi as a source of carbon and lead to increased growth compared to saturated fatty acids.
In principle, further HPTLC analyzes are recommended for the optimization of cosmetic formulations, in order to cover all combinations of germs and test substances. At least in the growth tests carried out, there was no change in growth with the formulations developed according to the principles mentioned above.
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Created: 2022Issued: 2023-03-09Updated: 2023-03-09
Faculty
Medizin
Publisher
Philipps-Universität Marburg
Language
ger
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DoctoralThesis
DFG-subjects
HautkrankheitenHautmikrobiomMalassezia HefenBakterienKosmetikaHilfsstoffeHautmikroflora
DDC-Numbers
610
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Müller, Bea Vanessa: Konzeption und Entwicklung eines Screeningverfahrens zur Identifizierung von für die Hautmikroflora problematischen Hilfsstoffen in Kosmetika. : Philipps-Universität Marburg 2023-03-09. DOI: https://doi.org/10.17192/z2023.0138.
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This item has been published with the following license: In Copyright