Applications and delivery mechanisms of hyaluronic acid used for topical/transdermal delivery – A review

The purpose of this review is to introduce the functionalities of hyaluronic acid (HA) and its potential application as an effective carrier for topical/transdermal delivery. Specifically, several delivery mechanisms of HA were summarized here in order to explain its potential permeation-enhancing roles for the skin, which includes receptor-based delivery pathway, skin hydration, hydrophobic interaction with stratum corneum, bioadhesive properties, and viscoelastic properties. To achieve the optimum delivery efficacy for bioactive compounds at different target layers of the skin, HA with various molecular weights and chemical modifications were applied to design different delivery systems, including hydrogel, nanoemulsion, microemulsion, prodrug, microneedle, liposome/hyalurosome. Delivery efficacy has been evaluated using in vitro Franz Cell Diffusion method and/or in vivo animal models. Throughout this review, it was confirmed that HA could be an effective carrier for both topical and transdermal deliveries due to its unique viscoelasticity, biocompatibility, biodegradability, non-immunogenicity, and biomedical benefits for the skin.