Non-invasive Intradermal Delivery of Hyaluronic Acid via Iontophoresis.

Hyaluronic acid (HA) is a hydrophilic supra-macromolecule, with a molecular weight (MW) 1000000<. HA is recognized as a biomaterial for skin moisturization. HA solution is typically injected into the skin using a needle. However, needle injection is invasive and does not result in homogeneous distribution of HA over a large area of skin. Therefore, non-invasive and effective technologies for homogenous intradermal delivery of HA are needed. Recently, we demonstrated the use of iontophoresis (ItP) for non-invasive intradermal delivery of various macromolecules, such as small interfering RNA (siRNA) (MW: 12000) and antibodies (MW: 150000). Based on our previous studies, we hypothesized that HA can also be delivered non-invasively into the skin by ItP. In this study, we applied ItP to fluorescence-labeled HA (MW: 600000-1120000 and 1200000-1600000) on rat dorsal skin. Following treatment, fluorescence was observed to be widely distributed in the skin, demonstrating successful intradermal delivery of HA via ItP. In addition, the relative moisture content and elasticity of skin treated with ItP/HA was temporarily higher than that of control skin. This is the first report demonstrating successful non-invasive intradermal delivery of HA and improvement of skin conditions by high-molecular weight HA delivered by ItP. In conclusion, ItP would be a useful technology for non-invasive intradermal delivery of high-molecular weight HA for treatment of skin diseases and cosmetology applications.