GHK Cu as a multifunctional copper peptide: synthesis routes, process engineering and emerging applications Systems Microbiology and Biomanufacturing Springer Nature Link GHK Cu as a multifunctional copper peptide: synthesis routes, process engineering and emerging applications Systems Microbiology and Biomanufacturing Springer Nature Link The Effect of the Human Peptide GHK on Gene Expression Relevant to Nervous System Function and Cognitive Decline Regenerative properties of the NL GHK Cu peptide and skin appearance Synthagen PL