It's plausible that more copper peptide reaches systemic circulation via injection than topical application, but "reaches circulation" and "produces a proportionally larger effect" aren't the same claim, and GHK's short serum half-life complicates the simple version of this comparison considerably
Effects of charge on antibody tissue distribution and pharmacokinetics
Membranes were probed with anti-GCLC sc-390811 (200 ng/ml), anti-ACTB sc-69879 (5 ng/ml), and anti-Vinculin sc-73614 (200 ng/ml), both from Santa Cruz Biotechonology (Santa Cruz, CA, USA) followed by goat anti-mouse IgG conjugated to IR-800Dye (926-32210
The amino acid sequence of GLP-1 analogues is less than 50
This modification significantly improves oral bioavailability and stability without changing the peptide biological activity once it reaches target tissues
this period was chosen because the reimbursement for GLP-1RAs in Taiwans NHI program began in 2011