Microneedles are a promising and minimally invasive transdermal delivery technique effective in promoting peptide permeation through the skin.

The needles have a size ranging from 100 to 1500 μm, which makes them able to pass through the stratum corneum (thickness between 10 and 30 μm).

Furthermore, they are responsible of forming pores in the skin, which are large enough to allow macromolecules to pass through, simply and painlessly.

Despite the advantages of this notable approach, microneedles have an obstacle when it comes to the delivery of substances: the elasticity of the skin. This parameter may hinder the penetration of microneedles in the stratum corneum, since the skin, can deform with the pressure exerted by the needle, without breaking its barrier. Consequently, pore formation and substance permeation are compromised.

There are some studies suggesting that different microneedles allow successful permeation of peptides into the skin. An in vitro study was performed by Zhang et al., to investigate the efficacy of solid microneedle arrays (consisting of 121 needles, attached to an applicator) in delivering hydrophilic peptides, namely acetyl hexapeptide-3, into pig ear skin. The results of the study exhibited not only that this physical system was effective in forming pores, but also in the delivery of the peptides through the skin, since the passive flow of acetyl hexapeptide 3 through the skin, when microneedles were applied was 0.44 ± 0.12 μmoL/cm/h, which was much higher than the passive flow of this peptide in untreated skin (0.014 ± 0.002 μmoL/cm/h).

Source: Journal of Drug Delivery Science and Technology - Anti-aging peptides for advanced skincare: Focus on nanodelivery systems