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Researchers dont think so, and the gene expression data backs them up

The bioavailability difference between the two routes compounds the distinction: topical application creates a localized skin depot, while injection delivers the peptide systemically at concentrations impossible to achieve through the skin barrier

GHK-Cu is unusual because it operates as a biological reset signal modulating thousands of genes simultaneously, activating the skin's own repair intelligence rather than forcing a single response

No need to suffer following old textbooks

Guo X, Song J, Guan T et al (2015) Characterization of recombinant human gastrointestinal glutathione peroxidase mutant produced in Escherichia coli

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