The study found that using tiny solid microneedle patches on skin makes it easier for small protein-like molecules, including acetyl‑hexapeptide‑3, to pass through the skin. The effect was stronger for smaller peptides and seemed linked to the flow of water through the skin.

The aims of this study were to investigate the utility of solid microneedle arrays (150 µm in length) in enhancing transdermal delivery of peptides and to examine the relationship between peptide permeation rates and D2O flux. Four model peptides were used (Gly-Gln-Pro-Arg [tetrapeptide-3, 456.6 Da], Val-Gly-Val-Ala-Pro-Gly [hexapeptide, 498.6 Da], AC-Glu-Glu-Met-Gln-Arg-Arg-NH2 [acetyl hexapeptide-3, 889 Da] and Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2 [oxytocin, 1007.2 Da]). The influence of microneedle pretreatment on skin permeation was evaluated using porcine ear skin with Franze diffusion cell. Peptide permeation across the skin was significantly enhanced by microneedle pretreatment, and permeation rates were dependent on peptide molecular weights. A positive correlation between D2O flux and acetyl hexapeptide-3 clearances suggests that convective solvent flow contributes to the enhanced transdermal peptide delivery. It is concluded that solid microneedle arrays are effective devices to enhance skin delivery of peptides.