Few cosmetic peptides have a research history quite like GHK-Cu.

For decades, scientists have investigated this small copper peptide in connection with fibroblasts, collagen, extracellular matrix components, matrix remodeling and keratinocytes.¹ ² ³ ⁴

The interest in GHK-Cu does not come from one isolated experiment. Similar themes appear across different research models.

GHK-Cu has been studied in fibroblasts, the cells responsible for producing much of the dermal extracellular matrix.¹ Researchers have reported effects involving collagen and glycosaminoglycans.¹ ³ Other experiments have examined matrix turnover through MMPs and TIMPs, as well as keratinocyte biology.² ⁴ Human research has also produced early signals involving procollagen and measured wrinkle parameters.⁷ ⁸

Taken together, there are good scientific reasons to study GHK-Cu in skin.

The more difficult question is how much of this biology translates into visible results when GHK-Cu is applied topically to human skin.

That is where the evidence becomes smaller, and where formulation starts to matter.

Short answer: What does the evidence say about GHK-Cu for skin?

There are good scientific reasons to be interested in topical GHK-Cu.

The experimental research behind the molecule is unusually broad for a cosmetic peptide. GHK-Cu has been investigated in relation to fibroblasts, collagen, extracellular matrix components, matrix remodeling and keratinocyte biology.¹ ² ³ ⁴ Experimental human skin research also supports topical delivery under defined conditions.¹⁵ ¹⁶

There are human findings as well.

Small studies have reported a procollagen response following topical use of a copper peptide cream and improvements in measured wrinkle parameters with a specific GHK-Cu formulation.⁷ ⁸

What the research cannot yet tell us is one predictable effect size, one optimal concentration or how every GHK-Cu serum will perform.

The current picture is therefore promising: a substantial experimental foundation, evidence that topical delivery is possible under specific conditions, and early human signals worth investigating further.

The next question is how reliably that potential can be translated into a finished topical formulation.

Evidence at a glance

What are GHK, GHK-Cu and Copper Tripeptide-1?

GHK, GHK-Cu and Copper Tripeptide-1 are closely related terms, but they are not interchangeable in every research context.

GHK

GHK stands for glycyl L histidyl L lysine.

It is a tripeptide composed of three amino acids: glycine, histidine and lysine. GHK was originally identified in human plasma and was later shown to have a strong affinity for copper ions.⁹ ¹⁰

GHK-Cu

When GHK coordinates copper, it forms the complex generally described in the scientific literature as GHK-Cu.

The distinction between GHK and GHK-Cu can matter experimentally.

Siméon et al., for example, investigated matrix metalloproteinase 2 in cultured fibroblasts. The effect observed with GHK-Cu could also be reproduced by copper ions, but not by GHK alone.²

This is why the exact material used in a study needs to be considered when interpreting the result.

Copper Tripeptide-1

Copper Tripeptide-1 is the cosmetic ingredient terminology associated with the copper complex of Tripeptide-1 and corresponds to the GHK-Cu concept discussed throughout much of the skincare literature.

Historical terminology is less consistent. Older studies may refer to GHK-Cu, copper GHK, copper tripeptide or a copper binding peptide.

Material identity, concentration, purity and formulation should therefore be checked before results from different studies are treated as equivalent.

Copper peptides

Copper peptides are a broader category.

GHK-Cu is a copper peptide. Not every copper peptide is GHK-Cu.

Why did GHK-Cu become scientifically interesting?

GHK-Cu attracted scientific attention because different lines of research connected it with extracellular matrix biology and cells involved in skin structure.

An important early finding came from Maquart et al. in 1988.

The researchers exposed cultured fibroblasts to GHK-Cu and reported increased collagen synthesis under the conditions studied.¹

Later research widened the picture.

Studies investigated glycosaminoglycans, matrix metalloproteinases and their inhibitors, keratinocytes and experimental models characterized by active extracellular matrix turnover.² ³ ⁴ ⁵

A common theme can be traced through much of this work:

fibroblasts → extracellular matrix → matrix remodeling → skin structure biology

GHK-Cu is therefore more interesting scientifically than the familiar description of it as simply a “collagen peptide” suggests.

The GHK-Cu Evidence Ladder

A laboratory finding and a finished cosmetic product sit at very different levels of evidence.

For GHK-Cu, those levels can be thought of as an Evidence Ladder:

GHK biology → GHK-Cu biology → Topical delivery → Effects in human skin → Visible cosmetic outcomes → Specific concentration and formulation → Finished product

Each step requires additional evidence.

An effect in cultured fibroblasts does not show that topical application produces the same effect in living human skin.

Evidence that GHK-Cu can enter human skin does not by itself demonstrate a visible cosmetic outcome.

A clinical result obtained with a specialized delivery system belongs to the formulation that was actually tested.

And research on GHK-Cu as an ingredient does not establish the clinical performance of Leverium Cu3.

The distance between an experiment and the claim drawn from it can be described as the translational distance of the evidence.

The closer the experiment is to the actual product and outcome being discussed, the stronger the inference can become.

Extracellular Matrix Biology: The Mechanistic Rationale

The experimental literature around GHK-Cu extends beyond collagen. 

It includes fibroblasts, glycosaminoglycans and the processes involved in extracellular matrix turnover.

Skin structure is dynamic. Matrix components are continually synthesized, organized, modified and broken down.

GHK-Cu has been studied at several points within this system.

Fibroblasts and collagen

Evidence level: human fibroblast cell culture

Fibroblasts are major contributors to the extracellular matrix of the dermis.

In the 1988 experiment by Maquart et al., GHK-Cu increased collagen synthesis in fibroblast cultures.¹

The response began at very low experimental concentrations and reached its maximum around 10⁻⁹ M under the conditions studied.

The concentration response is worth noting because it was not simply linear. Increasing the experimental concentration did not continuously increase collagen synthesis.

This cell culture experiment demonstrates biological activity in fibroblasts.

It does not define an optimal percentage for a topical cosmetic formulation.

Glycosaminoglycans and the extracellular matrix

Evidence level: human fibroblast cell culture

Collagen is only one component of the extracellular matrix.

Wegrowski et al. investigated GHK-Cu in cultured normal human fibroblasts in 1992.³

They reported increased synthesis of total glycosaminoglycans, with effects involving dermatan sulfate and heparan sulfate.

The response was again biphasic. At higher experimental concentrations, synthesis progressively returned towards control levels.

The finding is another reminder that experimental GHK-Cu biology does not follow a simple rule in which more peptide necessarily produces a greater response.

Matrix remodeling: MMPs and TIMPs

Evidence level: human fibroblast cell culture

Matrix metalloproteinases, known as MMPs, participate in extracellular matrix turnover. TIMPs, or tissue inhibitors of metalloproteinases, regulate MMP activity.

Siméon et al. reported increased MMP 2 expression after exposing cultured fibroblasts to GHK-Cu. They also reported increased secretion of TIMP 1 and TIMP 2.²

These results should not be reduced to the idea that increasing or decreasing one MMP is necessarily desirable.

They place GHK-Cu within research on both matrix production and matrix turnover.

That broader remodeling context is one of the more distinctive features of the experimental literature around the peptide.

Keratinocyte biology

Evidence level: cultured human keratinocytes and skin equivalent models

Research on GHK-Cu is not limited to fibroblasts.

Kang et al. studied copper GHK in cultured keratinocytes and human skin equivalent models.⁴

They reported increased keratinocyte proliferation and changes in markers including integrin α6, integrin β1, PCNA and p63 under the experimental conditions.

The study adds another dimension to the experimental picture around GHK-Cu.

It does not demonstrate “stem cell activation” or “cellular rejuvenation” in people using topical GHK-Cu. Those interpretations extend beyond the measurements made in the experiment.

What does human topical research show?

The GHK-Cu literature includes human findings as well as laboratory research.

In Abdulghani et al., seven of ten participants receiving a copper peptide cream showed the defined procollagen response after one month.⁷

In Badenhorst et al., a specific GHK-Cu formulation produced larger changes in measured wrinkle parameters than comparator formulations after eight weeks.⁸

These findings are particularly interesting because they move beyond cell culture and into topical human research.

The limitation is scale. The human literature is still too small and formulation specific to establish one universal effect size for topical GHK-Cu.

A systematic review published by Mokhtar et al. in 2026 illustrates this gap. Within its specific search strategy and eligibility criteria, the authors identified 20 eligible studies, of which 18 were preclinical and two were randomized controlled trials.⁶

This is not a census of every historical publication involving copper peptides. It does, however, show how much larger the experimental literature remains than the modern clinical literature.

Key human topical studies

These studies address different questions and used different formulations. Their results should therefore be interpreted individually rather than pooled into a single estimate of what “GHK-Cu does.”

Does GHK-Cu increase collagen in human skin?

There is a human signal connecting topical copper peptide use with procollagen. The evidence does not show that GHK-Cu increased human skin collagen by 70 percent.

The distinction comes from the way the original study reported its results.

What Abdulghani et al. actually found

The 1998 study included 20 healthy participants and lasted one month.⁷

Ten participants applied tretinoin to one thigh and vitamin C to the other.

Another ten applied melatonin to one thigh and a cream containing a glycyl L histidyl L lysine copper tripeptide complex to the other.

Biopsies were used to examine changes including dermal procollagen synthesis.

A significant procollagen response was observed in:

4 of 10 participants treated with tretinoin

5 of 10 participants treated with vitamin C

5 of 10 participants treated with melatonin

7 of 10 participants treated with the copper peptide cream⁷

The last figure appears to be the source of a claim that is now frequently repeated online.

COMMON ONLINE CLAIM

“GHK-Cu increases collagen by 70%.”

WHAT THE STUDY ACTUALLY REPORTED

Seven of ten participants receiving the copper peptide cream showed the defined procollagen response.

The 70 percent figure describes the proportion of participants who showed that response.

It does not describe a 70 percent increase in the quantity of collagen.

The underlying finding remains notable: a small human study detected a procollagen response in most participants receiving the copper peptide cream.

Does topical GHK-Cu reduce wrinkles?

Small human studies provide positive wrinkle related signals for specific GHK-Cu formulations. The size of the reported effects needs to be read together with the study design and the way the numbers were calculated.

The 2016 Badenhorst study is particularly useful here.⁸

Forty women aged 40 to 65 entered the randomized double blind study. Thirty nine completed it.

The experimental GHK-Cu formulation used a lipid based nanocarrier.

After eight weeks, larger changes in measured wrinkle parameters were reported with the experimental formulation than with its comparators.

For wrinkle volume, the mean change from baseline in the relevant comparison was approximately:

24.1% with the GHK-Cu formulation

compared with

**15.0% with the control formulation.**⁸

The paper also reports a **55.8% relative improvement compared with control.**⁸

Those figures are not interchangeable.

COMMON ONLINE CLAIM

“GHK-Cu reduces wrinkles by 55.8%.”

WHAT THE STUDY ACTUALLY REPORTED

The GHK-Cu formulation showed an approximately 24.1% mean reduction in wrinkle volume from baseline in the relevant comparison. The 55.8% figure describes the relative improvement compared with the response observed with control.⁸

It should not be read as 55.8 percent of an individual's wrinkle volume disappearing.

The formulation is relevant too.

The experiment tested GHK-Cu in a lipid based nanocarrier. The result therefore belongs to that experimental formulation and cannot automatically be assigned to every serum containing GHK-Cu.

What about studies with mixed results?

Not every human study has produced a clear objective advantage for GHK-Cu.

Miller et al. investigated GHK-Cu containing skincare following CO₂ laser resurfacing.¹³

Thirteen participants completed the study.

Computer analysis and blinded evaluation did not show a statistically significant advantage for earlier resolution of erythema.

Both groups improved in wrinkles and overall skin quality following laser resurfacing, but objective assessment did not demonstrate significant differences between the groups for those measures.

Patient reported satisfaction with overall skin quality was higher in the GHK-Cu group.¹³

The result is mixed, but the experimental setting also matters.

Skin following CO₂ laser resurfacing has a disrupted barrier and differs substantially from intact skin during routine cosmetic use. The study therefore answers a different question from a conventional facial skincare trial.

The GHK-Cu Claim Audit

Some of the most familiar numbers associated with GHK-Cu have drifted away from what the original studies actually measured.

The original results are often interesting enough without the inflated interpretation.

Removing the exaggerated versions does not make the research less interesting.

It makes the evidence easier to understand.

Can GHK-Cu penetrate human skin?

Experimental human skin research has demonstrated penetration and retention of the tested copper tripeptide under defined conditions. The amount delivered depends on the experimental system and formulation, and penetration alone does not demonstrate a cosmetic outcome.

Skin is an effective barrier.

Whether a peptide enters it depends on more than molecular weight. Molecular size, charge, hydrophilicity, lipophilicity, chemical form, vehicle, concentration, stability, skin condition and exposure time can all influence delivery.

Hostynek, Dreher and Maibach investigated copper applied as glycyl L histidyl L lysine cuprate diacetate using human skin ex vivo.¹⁵ ¹⁶

Their experiments demonstrated measurable penetration and retention of copper applied as the tripeptide under the conditions studied.

This provides experimental evidence that topical delivery is possible.

It does not show that every commercial GHK-Cu serum produces equivalent penetration, nor does penetration alone demonstrate that a sufficient amount reaches a particular biological target to produce a visible cosmetic result.

A precise reading of the evidence is therefore:

Topical delivery of GHK-Cu has been demonstrated under specific experimental conditions. Its extent and relevance depend on the formulation and exposure conditions.

Why formulation matters

The molecule is only one part of a topical product.

Once GHK-Cu moves from an experimental system into a cosmetic formulation, additional variables enter the equation:

ingredient identity

concentration

vehicle

pH

stability

interactions with other ingredients

preservation

packaging

manufacturing

skin compatibility

actual exposure after application

This is why two products containing the same named ingredient are not necessarily equivalent from an evidence perspective.

What about concentration?

No universally optimal topical concentration of GHK-Cu has been established in robust human dose response trials.

The laboratory literature itself argues against an overly simple interpretation of concentration.

The collagen experiment by Maquart et al. and the glycosaminoglycan study by Wegrowski et al. both reported responses that were not simply linear as experimental GHK-Cu concentrations increased.¹ ³

Those cell culture concentrations cannot be converted directly into percentages for a topical serum.

Between the concentration in a bottle and exposure within skin are several steps:

formulation → application → skin surface → barrier → distribution → local availability → biological response

A higher concentration can change exposure.

Current evidence does not establish a proportional relationship between the percentage printed on a cosmetic product and the visible result it will produce.

What about the vehicle?

The Badenhorst study offers a useful example of why vehicle deserves attention.⁸

Its GHK-Cu was incorporated into a lipid based nanocarrier.

If a delivery system alters how an ingredient interacts with or enters the skin, the resulting clinical finding belongs to the complete formulation that was tested.

Formulation is part of the evidence.

What does wound research tell us about GHK-Cu?

Experimental wound research forms an important part of the scientific history of GHK-Cu. It does not establish that a cosmetic GHK-Cu serum treats wounds.

Research context. Not a product claim.

In 1993, Maquart et al. investigated GHK-Cu in an experimental wound chamber model in rats.⁵

They reported concentration dependent increases in several measures of connective tissue accumulation, including collagen and glycosaminoglycans.

Alongside the fibroblast research, these experiments helped establish interest in GHK-Cu in biological environments characterized by substantial extracellular matrix activity and remodeling.

The model is useful for understanding the research history of the molecule.

It is not equivalent to routine cosmetic use on intact skin. A wound has a disrupted barrier, different cellular signaling and a different exposure environment.

The wound literature therefore contributes to the mechanistic research around GHK-Cu.

How strong is the evidence overall?

GHK-Cu has a substantial experimental foundation, experimental support for topical delivery and early human signals.

The largest gap lies between this biological research and predictable, independently replicated cosmetic outcomes.

This is the current scientific position of GHK-Cu: a well developed experimental story with encouraging points of translation into human topical research, but important clinical questions still open.

What we still do not know

Many of the open questions around GHK-Cu now concern translation rather than whether the molecule can produce biological effects in experimental systems.

Among the most relevant are:

What topical concentration provides useful exposure in a well designed formulation?

How much intact GHK-Cu reaches biologically relevant targets after normal topical application?

When do specialized delivery systems matter?

How large are cosmetic effects in larger independent trials?

Which experimentally observed mechanisms contribute most to visible outcomes?

How directly can results from one GHK-Cu formulation be compared with another?

Answering these questions would close some of the distance between the experimental literature and routine topical use.

What would a particularly informative GHK-Cu trial look like?

A strong future trial would ideally be independently conducted, preregistered, adequately powered, randomized, vehicle controlled and appropriately blinded.

The formulation and GHK-Cu concentration should be fully characterized. Objective instrumental endpoints, standardized photography and blinded assessments would improve interpretation, while sufficient duration would allow meaningful cosmetic changes to be evaluated.

Connecting formulation analytics and skin exposure with cosmetic outcomes would be especially valuable.

Such a design could begin to answer one of the central questions around topical GHK-Cu:

How reliably can its experimental biology be translated into measurable human cosmetic outcomes?

Safety and tolerability

Available human studies provide some tolerability information for the formulations and exposure periods that were actually studied.

They do not establish universal or long term tolerability for every GHK-Cu formulation.

Ingredient research can provide information about the molecule. Human studies provide information about the specific formulation and exposure period investigated.

A finished cosmetic introduces additional variables including concentration, preservation, pH, supporting ingredients, stability, packaging and manufacturing.

Finished product safety therefore needs to be assessed at the product level rather than inferred solely from research on the ingredient.

What does this evidence mean for Leverium Cu3?

The research discussed above explains the scientific interest surrounding GHK-Cu. Leverium Cu3 contains GHK-Cu within our own finished cosmetic formulation.

Findings from other GHK-Cu formulations should not be interpreted as demonstrated effects of Cu3.

Cu3 Edition 1 is formulated with:

3% GHK-Cu

pH 5.0 to 6.0

Ectoin

Panthenol

Hyaluronic Acid

No fragrance

No alcohol

30 ml

Why did we formulate Cu3 with 3% GHK-Cu?

Three percent is a formulation specification chosen for Cu3 Edition 1.

It is not presented as a clinically established optimum or as a concentration demonstrated to produce a particular cosmetic outcome.

Current human evidence does not establish that 3% is the optimal topical concentration, nor that a 3% formulation must produce three times the effect of a 1% formulation.

Concentration is one variable within the complete formulation.

Why a defined pH?

Cu3 is manufactured to a defined pH specification.

This provides a measurable and controlled parameter for the finished formulation.

We do not infer from this that the exact pH range of Cu3 has been clinically demonstrated to maximize GHK-Cu efficacy.

Why Ectoin, Panthenol and Hyaluronic Acid?

These ingredients are included as supporting components of the complete formulation.

Their presence is not presented as evidence of a clinically demonstrated synergy with GHK-Cu.

Why no fragrance or alcohol?

Cu3 is formulated without fragrance and without alcohol.

These are deliberate formulation choices.

They do not establish universal freedom from irritation.

Research on GHK-Cu explains the scientific interest in the ingredient.

Evidence for a finished formulation has to be considered separately.

Research evolves. So can the formula.

Edition 1 represents our current formulation decision based on the evidence, formulation knowledge and quality standards available today.

New research may improve our understanding of concentration, topical delivery, raw materials, analytical methods, stability, formulation interactions or cosmetic outcomes.

Meaningful new evidence can therefore inform future formulation decisions.

Edition 1 is not an experimental or unfinished formula.

It is our current formulation of Cu3, based on what we know today.

Final perspective

GHK-Cu has an unusually rich research history for a cosmetic peptide.

Experimental studies connect it with fibroblasts, collagen, glycosaminoglycans, matrix turnover and keratinocyte biology.¹ ² ³ ⁴ 

Experimental tissue remodeling research adds further biological context.⁵ Human skin experiments show that topical delivery is possible under specific conditions.¹⁵ ¹⁶ Human studies have also reported early signals involving procollagen and measured cosmetic outcomes.⁷ ⁸

That is enough to make GHK-Cu scientifically really interesting.

It is not enough to close every question.

The experimental foundation remains considerably broader than the modern human cosmetic literature. The questions that matter now are increasingly practical:

Which formulation?

Which concentration?

Which delivery profile?

Which measurable human outcome?

How reproducible is the result?

These are the questions that connect ingredient research with formulation science and, eventually, with evidence for finished products.

GHK-Cu does not need exaggerated numbers to make a compelling case for further study.

The research itself already gives us good reasons to keep looking.

Methodology

This article is a critical evidence synthesis, not a formal systematic review or meta analysis.

Its purpose is to examine the scientific basis surrounding topical GHK-Cu while keeping mechanistic research, topical delivery, human evidence, formulation specific findings and finished product claims separate.

Primary publications were prioritized for central scientific claims.

Recent reviews were used to map the wider literature, identify relevant studies and trace commonly repeated claims towards their original sources.

Literature reviewed through: 7 September 2026

Last reviewed: 7 September 2026

Author: Lukas Manfred Heck

References

1. Maquart FX, Pickart L, Laurent M, Gillery P, Monboisse JC, Borel JP. Stimulation of collagen synthesis in fibroblast cultures by the tripeptide copper complex glycyl L histidyl L lysine Cu²⁺. FEBS Letters. 1988;238(2):343 to 346. DOI: 10.1016/0014-5793(88)80509-X. PMID: 3169264.

2. Siméon A, Emonard H, Hornebeck W, Maquart FX. The tripeptide copper complex glycyl L histidyl L lysine Cu²⁺ stimulates matrix metalloproteinase 2 expression by fibroblast cultures. Life Sciences. 2000;67(18):2257 to 2265. DOI: 10.1016/S0024-3205(00)00803-1. PMID: 11045606.

3. Wegrowski Y, Maquart FX, Borel JP. Stimulation of sulfated glycosaminoglycan synthesis by the tripeptide copper complex glycyl L histidyl L lysine Cu²⁺. Life Sciences. 1992;51(13):1049 to 1056. DOI: 10.1016/0024-3205(92)90504-I. PMID: 1522753.

4. Kang YA, Choi HR, Na JI, Huh CH, Kim MJ, Youn SW, Kim KH, Park KC. Copper GHK increases integrin expression and p63 positivity by keratinocytes. Archives of Dermatological Research. 2009;301(4):301 to 306. DOI: 10.1007/s00403-009-0942-X. PMID: 19319546.

5. Maquart FX, Bellon G, Chaqour B, Wegrowski J, Patt LM, Trachy RE, Monboisse JC, Chastang F, Birembaut P, Gillery P, et al. In vivo stimulation of connective tissue accumulation by the tripeptide copper complex glycyl L histidyl L lysine Cu²⁺ in rat experimental wounds. Journal of Clinical Investigation. 1993;92(5):2368 to 2376. DOI: 10.1172/JCI116842. PMID: 8227353.

6. Mokhtar J, et al. The Regenerative Potential of GHK-Cu in Aesthetic Medicine. Aesthetic Surgery Journal. Published online August 20, 2026. DOI: 10.1093/asj/sjag169. PMID: 42619529.

7. Abdulghani AA, Sherr A, Shirin S, Solodkina G, Morales Tapia E, Wolf B, Gottlieb AB. Effects of topical creams containing vitamin C, a copper binding peptide cream and melatonin compared with tretinoin on the ultrastructure of normal skin. Disease Management and Clinical Outcomes. 1998;1(4):136 to 141. DOI: 10.1016/S1088-3371(98)00011-4.

8. Badenhorst T, Svirskis D, Merrilees M, Bolke L, Wu Z. Effects of GHK-Cu on MMP and TIMP expression, collagen and elastin production, and facial wrinkle parameters. Journal of Aging Science. 2016;4:166. DOI: 10.4172/2329-8847.1000166.

9. Pickart L, Thaler MM. Tripeptide in human serum which prolongs survival of normal liver cells and stimulates growth in neoplastic liver. Nature New Biology. 1973;243:85 to 87. PMID: 4349963.

10. Pickart L, Freedman JH, Loker WJ, Peisach J, Perkins CM, Stenkamp RE, Weinstein B. Growth modulating plasma tripeptide may function by facilitating copper uptake into cells. Nature. 1980;288:715 to 717. DOI: 10.1038/288715a0. PMID: 7453802.

11. Leyden J, Stephens T, Finkey M, Barkovic S. Skin Care Benefits of Copper Peptide Containing Eye Creams. Proceedings of the American Academy of Dermatology 60th Annual Meeting. New Orleans; 2002. Conference proceedings.

12. Leyden J, Stephens T, Finkey M, Appa Y, Barkovic S. Skin Care Benefits of Copper Peptide Containing Facial Cream. Proceedings of the American Academy of Dermatology 60th Annual Meeting. New Orleans; 2002. Conference proceedings.

13. Miller TR, Wagner JD, Baack BR, Eisbach KJ. Effects of topical copper tripeptide complex on CO₂ laser resurfaced skin. Archives of Facial Plastic Surgery. 2006;8(4):252 to 259. DOI: 10.1001/archfaci.8.4.252. PMID: 16847171.

14. Pickart L, Margolina A. Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. International Journal of Molecular Sciences. 2018;19(7):1987. DOI: 10.3390/ijms19071987. PMID: 29986520.

15. Hostynek JJ, Dreher F, Maibach HI. Human skin retention and penetration of a copper tripeptide in vitro as function of skin layer towards anti inflammatory therapy. Inflammation Research. 2010;59(11):983 to 988. DOI: 10.1007/s00011-010-0214-4. PMID: 20703511.

16. Hostynek JJ, Dreher F, Maibach HI. Human skin penetration of a copper tripeptide in vitro as a function of skin layer. Inflammation Research. 2011;60(1):79 to 86. DOI: 10.1007/s00011-010-0238-9.

17. López Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G. Hallmarks of Aging: An Expanding Universe. Cell. 2023;186(2):243 to 278. DOI: 10.1016/j.cell.2022.11.001. PMID: 36599349.

18. Mortazavi SM, Mohammadi Vadoud SA, Moghimi HR. Topically applied GHK as an anti wrinkle peptide: advantages, problems and prospective. BioImpacts. 2025;15:30071. Published online 2024. DOI: 10.34172/bi.30071. PMID: 39963574.