Skin is the versatile target for macromolecular medicines. However, since stratum corneum is tight barrier of skin, non-invasive transdermal delivery of macromolecules is difficult. Recently, iontophoresis is known as a non-invasive transdermal delivery technology. Iontophoresis can deliver ionic molecules by using faint electricity (0.3-0.5 mA/cm2). Although it has been considered that iontophoresis delivers only small ionic molecules, we succeeded in the delivery of macromolecules and nanoparticles by iontophoresis (Kajimoto et al., Int J Pharm 2011). In addition, we found that faint electricity opens intercellular junction via activation of cell signaling pathway (Hama e t al., J Biol Chem 2014). Based on these findings, we examined transdermal delivery of various polymer nanoparticles by iontophoresis. We tried the iontophoresis of antigen peptide-loaded nanogels, which are polymer-based nanoparticle, for anti-cancer vaccination. Iontophoresis resulted in the accumulation of the peptide and nanogels in the epidermis, and subsequent increase in the number of Langerhans cells in the epidermis. Moreover, tumor growth was significantly suppressed by iontophoresis of the antigen peptide-loaded nanogels (Fig.A, Toyoda et al., Int J Pharm 2015). Alternatively, we tried the iontophoresis of redox nanoparticles (RNPs) for prevention of UV-induced melanin production in the skin. RNPs containing nitroxide radicals as free radical scavengers were previously developed, and shown to be effective ROS scavengers in the body. RNPs are therefore expected to be useful for effective protection against UV-induced melanin production. RNPs were accumulated in the epidermal layer upon application of iontophoresis. Further, the combination of RNPs with iontophoresis decreased UV-induced melanin spots and melanin content in the skin (Fig. B, Shiota et al., Biol Pharm Bull 2017). In conclusion, iontophoresis of polymer nanoparticles, such as peptide-loaded nanogels and RNPs, would serve as an effective transdermal delivery system for various skin disorders.

Transdermal delivery of polymer nanoparticles via faint electricity

2019 Spring National Meeting

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