GHK Cu as a multifunctional copper peptide: synthesis routes, process engineering and emerging applications Systems Microbiology and Biomanufacturing Springer Nature Link Copper Peptide Hair Growth Serum for Hair Loss & Thinning Hair Feline Skinscience GHK Cu Peptide and Hair Follicle Growth Biotech Peptides The Effect of the Human Peptide GHK on Gene Expression Relevant to Nervous System Function and Cognitive Decline