GHK-Cu

GHK-Cu is a coordination complex of copper(II) with the naturally occurring human tripeptide glycyl-L-histidyl-L-lysine (Gly-His-Lys, GHK), supplied as a research chemical for in vitro and preclinical laboratory work and not approved for human or veterinary use.

Two closely related items circulate under overlapping names, and they are not interchangeable on paper or on the balance. GHK is the free tripeptide, a white lyophilised solid. GHK-Cu is the copper-loaded 1:1 complex, typically a blue to blue-violet solid whose colour comes from the d-d transitions of the bound Cu(II) ion. Catalogue listings, certificates of analysis, and published methods sometimes use "GHK-Cu" loosely for either species, so the first question about any lot is which of the two was synthesised and assayed.

Specifications

Research history

The peptide entered the literature through liver cell culture rather than through skin or metal biology. Pickart and Thaler (1973), reporting in Nature New Biology, described a low-molecular-weight fraction of human serum that altered the behaviour of cultured hepatocyte preparations, prolonging survival of normal liver cells while increasing growth of a cultured hepatoma line; the active species was later characterised as the tripeptide glycyl-histidyl-lysine. This is an in vitro observation from 1973 and has not been reproduced as a clinical finding.

Interest shifted to connective tissue in the 1980s. Maquart et al. (1988), in FEBS Letters, examined GHK-Cu in cultured fibroblasts and reported that the effect on collagen synthesis began between 1 and 10 pM, was maximal at 1 nM, and was independent of any change in cell number. The abstract states no magnitude for that change, and percentage figures attributed to this paper in secondary sources are not traceable to it, so none is quoted here. The result is an in vitro observation in cultured cells.

Structural chemistry followed. Hureau et al. (2011), in Chemistry – A European Journal, reported X-ray and solution structures of the Cu(II)-GHK complex alongside Cu(II)-DAHK, the ATCUN motif at the N-terminus of human serum albumin, and compared the redox properties of the two. That study described Cu(II)-GHK as dimeric in the solid state but monomeric in solution, with three nitrogen donors: the N-terminal amine, the deprotonated amide nitrogen between glycine and histidine, and the histidine imidazole. The fourth equatorial position is labile and was occupied by a carboxylate oxygen in the solid state. The lysine side chain is not part of the donor set, and the complex carries a net positive charge at physiological pH.

Mechanistic framing in the literature

Most published mechanistic discussion describes GHK as a copper-handling ligand rather than as a receptor agonist. No specific cell-surface receptor for GHK or GHK-Cu has been established in the peer-reviewed literature. The recurring model is exchange with albumin's high-affinity copper site and delivery of Cu(II) to copper-dependent enzymes, with downstream effects attributed to copper availability rather than to peptide signalling per se.

A separate strand of work is transcriptional. Pickart and Margolina (2018), in International Journal of Molecular Sciences, applied the Broad Institute Connectivity Map to GHK and reported that 31.2% of catalogued human genes showed expression changes of at least 50%, split approximately 59% increased and 41% suppressed. That analysis is a computational query against a pre-existing expression database, not a measurement in tissue, and the same authors note in that paper that compounds tested for effects on gene expression using computer-based tools often lack supporting biological data. The same group's 2015 review in BioMed Research International reports plasma GHK at about 200 ng/mL at age 20, declining to 80 ng/mL by age 60, a correlational observation rather than a demonstrated mechanism.

Animal model findings

Several rodent studies have examined GHK-Cu in induced-injury models, all preclinical:

• Park et al. (2016), in Oncotarget, studied the complex in cultured RAW 264.7 macrophages and in lipopolysaccharide-induced acute lung injury in mice.
• Fu et al. (2015), in the Journal of Orthopaedic Research, evaluated GHK-Cu(II) in a rat anterior cruciate ligament reconstruction model; the published title characterises the effect on healing outcome as transient, and group differences present at 6 weeks were absent at 12. That qualifier is worth carrying forward whenever the study is cited.
• Bian et al. (2024), in Redox Biology, examined the complex in a murine silicosis model and in alveolar macrophages, with peroxiredoxin 6 proposed as a molecular target.

These are murine and rat results in induced-injury paradigms. None of them is a human study, and none of them was designed to establish clinical efficacy.

Limits of the current evidence

There are no adequate, well-controlled human trials establishing efficacy of GHK-Cu for any indication. The human-subject literature that exists is concentrated in small topical cosmetic evaluations using heterogeneous vehicle formulations at varying concentrations, frequently with commercial sponsorship, and is not directly informative about any other context. A further consideration is bibliographic: much of the mechanistic review literature originates from a small, closely related set of authors, so breadth of citation does not necessarily indicate independent replication.

Copper chemistry imposes its own caution. Labile copper is redox-active and participates in Fenton-type chemistry, so effects reported for a copper complex depend strongly on concentration, buffer, competing ligands, and reductants. Hureau et al. reported that both Cu(II)-GHK and Cu(II)-DAHK are inert under moderate redox potentials, but that Cu(II)-GHK could be reduced with subsequent release of the copper ion. In vitro results obtained at picomolar to nanomolar concentrations in defined media do not extrapolate cleanly to other systems.

Analytical identity and documentation

Because two species share the common name, documentation for GHK-Cu should resolve the ambiguity explicitly. A complete package generally includes reversed-phase HPLC purity with the chromatogram, mass confirmation by LC-MS or MALDI against the target mass for the species claimed, copper content by ICP-MS or atomic absorption to establish stoichiometry, water content by Karl Fischer, and counter-ion identity (acetate or trifluoroacetate) with residual solvent data. Copper stoichiometry is the item most often absent from GHK-Cu paperwork; without it a blue powder is not distinguishable on paper from a physical mixture. Reading these documents is covered under lab testing.

Handling and storage

The lyophilised solid is stored at −20 °C, desiccated, and protected from light. Copper complexes are sensitive to moisture, light, and reducing conditions; discolouration or fading of the blue tint indicates that the material has changed and warrants re-analysis. Solution stability is much shorter than solid-state stability, and repeated freeze-thaw is a common source of variability between experiments. General practice for solid and reconstituted reference materials is covered under peptide storage and reconstitution; concentration arithmetic for in vitro stock preparation can be worked through with the peptide calculator.

Regulatory status

GHK-Cu is not approved by the FDA as a drug for any indication in the United States, and it is not a dietary ingredient. It does appear as a cosmetic ingredient under the INCI name Copper Tripeptide-1; cosmetic ingredient listing is a separate regulatory category from drug approval and says nothing about any other use or purpose. The regulatory posture toward research peptides in the United States has been changing, so current status should be confirmed against primary FDA sources. Material sold here is supplied for laboratory research only, and is not for human or animal consumption. See the research use policy.

FAQ

How does GHK-Cu differ from GHK?

GHK is the free tripeptide (C14H24N6O4, 340.38 g/mol, white solid). GHK-Cu is the 1:1 copper(II) complex (C14H22CuN6O4, approximately 401.9 g/mol, blue solid). They have different CAS numbers, different masses on LC-MS, and different handling sensitivities, and much of the published literature uses the names inconsistently.

What storage conditions apply?

Lyophilised solid at −20 °C, desiccated and shielded from light. The complex is moisture- and light-sensitive; loss of blue colour indicates a change in the material. Solutions are less stable than solids and should be analysed rather than assumed after storage.

Is GHK-Cu FDA approved?

No. It is not FDA approved as a drug for any indication and is not a dietary ingredient. It is used as a cosmetic ingredient under the INCI name Copper Tripeptide-1, which is a separate regulatory category and not an approval.

What should a certificate of analysis show?

Identity of the species assayed (free peptide or copper complex), HPLC purity with the chromatogram, mass confirmation, copper content establishing stoichiometry, water content, counter-ion identity, and residual solvent data. A COA that reports purity without reporting copper content leaves the central question about a copper complex unanswered.