The substance applied to a sample and the analyte measured afterward are not always the same thing. This skin experiment applied a copper–peptide preparation but quantified copper. Primary study
What the experiment showed
Researchers used flow-through diffusion cells and different preparations of excised human skin. Under sustained donor-exposure conditions, copper was detected in receiver fluid and retained in tissue after application of a GHK-Cu preparation. Inductively coupled plasma mass spectrometry provided elemental copper measurements. The experiment did not measure clinical anti-inflammatory benefit. Primary report
Our appraisal: follow the analyte
An elemental copper signal does not establish that all measured copper remained bound to the original peptide. Establishing intact-complex transport requires chemical-species information, not only total elemental abundance. Changes in binding partners within tissue are therefore relevant possibilities, not details that can be ignored.
Retention and passage through tissue are also different quantities. Copper remaining in a skin layer is not the same as copper recovered beyond that layer. Neither automatically equals systemic exposure in a living person.
The skin preparation matters. Isolated stratum corneum, separated epidermis, and dermatomed tissue have different structures and experimental vulnerabilities. Their permeability estimates should not be mixed as if they described one identical barrier.
The sustained donor conditions also differ from a finite application that dries, is rubbed off, or is washed away. Laboratory transport estimates therefore need careful translation to a finished product and intended use.
This study supports investigation of copper distribution under defined experimental conditions. It does not prove delivery of an unchanged complex to a therapeutic target, clinical efficacy, or a safe systemic exposure. The accessible report contains differing retention figures in its abstract and results; numerical depot estimates are withheld here pending reconciliation. Analytical identity and tissue preparation should remain central to any future quantitative summary.
Frequently asked questions
Was excised human skin used?
Yes.
What did the elemental assay measure?
Copper.
Does total copper identify intact GHK-Cu?
Not by itself.
Are retention and permeation the same quantity?
No.
Are all skin-layer preparations interchangeable?
No.
Was clinical anti-inflammatory efficacy tested?
No.
Why are depot quantities not reproduced here?
The accessible report's numerical presentation requires reconciliation.