28 TESTING
of the cellular, anatomical and functional continuity of the skin. Under normal conditions, the resulting
wound is repaired during wound healing, a complex process involving inflammation, cell proliferation, matrix deposition, and tissue remodelling. Another major focus around the preclinical
testing is the study of the extra-cellular matrix [ECM]. One of the personal care objectives are to maintain the skin in good conditions and preserve its elasticity and its resistance. ‘Firmness’ performance enhances the density of the dermal extra-cellular matrix [ECM]. This ‘renowned’ matrix plays one of the essential roles of the physical and biomechanical properties of the dermis with this intricate network of extracellular macromolecules providing cells structural, bioactive molecules and biochemical support. The ECM composed of hundred proteins is a dynamic network controlling the proliferation, adhesion, migration, polarity, differentiation, and apoptosis of the cells. The in vitro or ex vivo assays can target the various biological mechanisms providing a limitless opportunities of claims support. The major components of the ECM that
can be studied are: ■ Collagens, backbone of the tissue architecture, are fibril-forming [types I, II, III), non-fibrillar collagens (type IV), that composed a non-fibril network and fibril- associated collagens (types VI, IX, XII). ■ Glycosaminoglycans (GAGs), polysaccharides that help to keep water such as hyaluronic acid, keratan sulphate, chondroitin/dermatan sulphate, andheparan sulphate. ■ The laminins forming networks that interact with cell surface receptors. ■ The fibronectin fibrils acting like a ‘biological glue’. ■ Elastin fibres conferring elasticity and through cross-links with tropoelastin, desmosine or isodesmosine. This incredible network of substrates for matrix metalloproteinases (MMPs), stocks bioactive fragments and adhesive proteins is also modulated by exogenous environment. The own biochemical properties of the ECM can be studied in many ways through the analyse of its various components and their interaction and constitute a ‘gold’ support to substantiate ingredients and finished product claims. Another field of interest for the preclinical
assays is the study of the oxidative mechanisms in the epidermis and dermis. It plays a major role in the interface function of the skin to protect, through the life, our body from both endogenous and environment (UV, pollution etc.) stress. Free radicals and other oxidants can be generated by metabolic activity within the cell and by other environmental insults, providing biological damage to macromolecules, proteins, and fatty acids, resulting in detrimental properties for cells and their functioning. Oxidants and free radicals are a very important factor in causing premature
PERSONAL CARE June 2022
ageing and accelerating photoageing. Reactive oxygen species (ROS) are the most well-known free radical species, such as superoxide (O2
hydrogen peroxide (H2
-), hydroxyl radical (OH°) or O2
). Many studies have reported an increase
level of carbonylated proteins, which are end- products of oxidative stress, in the several layer of the skin. Moreover, polyunsaturated fatty acids are readily attacked by ROS, becoming oxidised into lipid peroxides which are toxic and capable of damaging most cells. Squalene, a lipid molecule in the sebum, is inclined to be oxidized under the environmental stress, due to its six double bonds. The oxidized product of squalene is malondialdehyde (MDA), a toxic molecule well known for its DNA damage and mutation effect and will lead to irreversible skin problem such as ageing.
These in tubo, in vitro or ex vivo tests can be performed on different supports depending on the specificity of the antioxidant activity that we want to demonstrate on firmness, pigmentation, wrinkles, hydration etc.
A limitless source of scientific communication Finally, the evaluation of active ingredients and cosmetic products is a sector that is at the centre of product developments and that intervenes at many stages from R&D, formulation to scientific communications. We see a close link between the testing industry and all components of product development, whether through ingredients, regulations, technologies, or consumer expectations. Brands wishing to expand into the vast
and ambitious Chinese market must comply with this new regulation. Testing laboratories in China must be accredited by Chinese authorities and certain claims such as hydration must follow protocols specifying the type of measuring device used.
The testing sector is seeing an increase in the importance of in vitro or ex vivo tests very often used to objectify raw materials or active ingredients, but which are increasingly used for finished products thanks to the reconstituted skin model. The performance of the products is evaluated on precise mechanisms of action with the almost infinite possibility of modulating alterations, concentrations, biomarkers, and methods of analysis. Scientific knowledge such as skin bio
printing, artificial intelligence, imaging, and neurosensory analysis increases the fields of investigation of the beauty industry with the possibility of multicentre studies conducted around the world on different ethical profiles. The global also becomes local to be more inclusive. Now the imaging of the skin from the
centimetre to the nanoscale is ever more crucial. Measuring the several elements and structure of the skin: water, lipids, dermal- epidermal junction, extracellular matrix, fibres etc. The various high-tech biometrological measurements give the opportunity to connect the technology with the new digital use of personalization from the shop to the bathroom. This connection between objectivation and the digital way of choosing and buying may bring the cosmeticians closer to the reality of marketing. Whether for ageing, radiance, biomechanical properties, or moisturising, the several techniques look for higher resolution, larger measurement area, non-invasive, no-contact, and direct methods. The algorithms and the statistics are the principal future contribution of the success of these new technologies. The combinations of classical biometric
measurements with more high-tech devices and specific biomarkers can provide a better understanding of the organisation of the skin structure and its functions.
PC
www.personalcaremagazine.com
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