GHK Cu as a multifunctional copper peptide: synthesis routes, process engineering and emerging applications Systems Microbiology and Biomanufacturing Springer Nature Link Unlocking the Secrets of GHK Cu: The Revolutionary Peptide for Youthfu GHK Cu and Erectile Dysfunction: What the Evidence Actually Shows The Effect of the Human Peptide GHK on Gene Expression Relevant to Nervous System Function and Cognitive Decline