Gold is one of the precious, softest, and electroconducting metals and, under certain conditions, forms stable colloids with nanoparticles that are easily absorbed by the skin. The bioavailability of those particles can be enhanced with polyethylene glycol, and they can be functionalized with peptides, providing complexes with improved efficiency and performance.
Thanks to their unique properties and versatility, colloidal gold nanoparticles are considered a promising delivery vehicle for pharmaceuticals and active cosmetic ingredients. They can overcome the skin barrier, which can be improved by physical methods such as microneedling or iontophoresis.
In its iconic form, gold (Au+ and Au3+) forms organic complexes and exhibits antimicrobial properties similar to those of silver ions. Studies testing the antimicrobial activity of colloid gold have shown that it is a weak antiseptic, and its effectiveness depends heavily on concentration and the presence of other antimicrobial agents. However, antiseptic or antibiotic agents conjugated to gold nanoparticles exhibited enhanced efficacy and anti-biofilm activity.
Thanks to functional groups such as amine, carboxyl, and thiol, amino acids can be capped onto gold nanoparticles, which opens vast opportunities for the development of gold-conjugated peptides with enhanced stability, permeability, and performance. With conjugation technology, the number of peptide-based complexes has been developed, such as:- MatriGold® - Palmitoyl Pentapeptide-4 (Matrixyl)
- Golden C® - Ascorbic Acid with Glutathione
- Golden Collagenine - Acetyl Heptapeptide-9 (mimics the TGFβ)
Colloidal gold is considered a safe ingredient for external use in cosmetic concentrations. However, the European Scientific Committee on Consumer Safety (SCCS) published an opinion stating that there is insufficient scientific data for its safety assessment, that systemic uptake of gold nanoparticles may lead to accumulation, and that it has the potential for adverse effects. Later in 2024, EC added it to the Annex II listing #1728 without specifying the criteria.
