90 SKIN CARE


keratinocytes in the granulosum layer of the epidermis and undergoes covalent crosslinking mediated by transglutaminase-3 (TGM3), resulting in the formation of the mature CE (Figure 1). Immunohistochemistry revealed the


presence of LCE6A in both the upper stratum granulosum and the lower SC of healthy human epidermis. Western blot analysis further unveiled diverse forms of LCE6A, including a 40-kDa band and higher molecular weight forms. These findings hint at potential crosslinking interactions with CE precursors such as involucrin or loricrin. In vitro assays provided insights into


TGM3’s capacity to form bridges with LCE6A, a phenomenon substantiates by in situ crosslinking assays conducted on frozen skin sections. Utilizing biotinylated peptides corresponding to specific LCE6A regions, the research underscored the significance of a consecutive glutamine- lysine sequence for the establishment of covalent bonds. Then, the study explored the mechanical


reinforcement potential of short biotinylated peptides derived from LCE6A sequences in a sonication assay, revealing their ability to protect CEs. Confirmation of the penetration of these


short peptides into the SC was established in an ex vivo assay, demonstrating their ability to reach the binding site at the interface between the stratum granulosum and the SC. These experiments strongly indicate the


pivotal role of LCE6A and its peptides in influencing the mechanical properties of CEs, offering promising implications for cosmetic applications.


Patented peptide obtained by green chemistry-based synthesis In response to the imperative for environmental responsibility within the cosmetic industry, Lucas Meyer Cosmetics has pioneered the development of a novel peptide that mimics the activity of LCE6A through a green chemistry- based synthesis, aligning with a life cycle approach. The synthesis of this innovative peptide, named the Hexapeptide-9 peptide and featuring Hexapeptide-9 as its key component, underwent a meticulous evaluation using an internal green chemistry tool designed for Lucas Meyer Cosmetics’ peptide technology. This innovative process not only optimizes nine out of the 12 recognized green chemistry principles but also reaffirms the company’s commitment to more eco-friendly practices. The Hexapeptide-9 peptide adheres to


key green chemistry principles, including atom economy, waste prevention, design for energy efficiency, use of solvents not classified as CMR (carcinogenic, mutagenic, or toxic to reproduction), and real-time pollution prevention. Utilizing alternative synthetic processes that


consume fewer amino acids, reduce waste, and operate at lower temperatures, this approach ensures faster peptide synthesis in solution, mainly at 20-40°C, and ambient pressure. Direct monitoring through HPLC prevents side


PERSONAL CARE April 2024 External


PROGRESSIVE STEPS IN THE FORMATION OF THE CORNIFIED EVELOPE


Desquamation


Cornification LCE6A synthesis


Lipid development


Starting the


differentiation process


Constant proliferation of keratinocytes


Stratum Basale


Stratum Corneum


Stratum Granulosum


Stratum Spinosum


Figure 1: Role of LCE6A in the cornification process


products and eliminates the need for elaborate qualitative tests. Moreover, adherence to principles such as


less hazardous synthesis, non-CMR solvents, and auxiliaries demonstrates the company’s commitment to safer chemistry and accident prevention. This involves avoiding hazardous solvents and reagents, promoting safer working conditions, significantly reducing solvent consumption, eliminating washing steps with organic solvents, and enabling isolation steps in water.


With 99.99% natural origin content (ISO


16128), Hexapeptide-9 peptide is readily biodegradable, friendly to aquatic ecosystems, and well-tolerated for cosmetic purposes at recommended usage levels.


Unique mechanism of action mimicking recently uncovered protein LCE6A Mimicking LCE6A protein activity, the Hexapeptide-9 peptide underwent comprehensive ex vivo testing for efficacy confirmation. The ability of the Hexapeptide-9 peptide


to be crosslinked was assessed in situ by endogenous TGM at the periphery of granular keratinocytes on human skin frozen sections. A fluorescent pure peptide was applied with or without a TGM activator (Ca2+) to trigger the crosslinking. After washing to eliminate the non-crosslinked peptides, crosslinked peptides were observed using fluorescence microscopy (Figure 2). The results distinctly illustrate a dose-


dependent effect, indicating that the peptides form crosslinks with corneocyte membrane proteins when TGM is activated. Notably, the absence of TGM activation prevents peptide crosslinking. Consequently, the Hexapeptide-9 peptide demonstrates a biomimetic function akin to LCE6A, contributing to the construction of the cornified envelope. Once crosslinking ability was confirmed, solidity was evaluated via sonication. It consists of applying a frequency wave to the corneocytes for destruction. Compared to the untreated condition, pure peptide treatment significantly decreases the number of damaged corneocytes by 27%, indicating a more robust cornified envelope. The impact of the Hexapeptide-9 peptide


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