Natural food-derived materials fabricated nanocapsules-dissolving microneedles system for treating primary dysmenorrhea

Low solubility, poor physicochemical stability and unpleasant odor are the main limitations for the application of some essential oils in the pharmaceutical and food industries. In this work, cinnamon oil (CIO) was encapsulated as oil phase with soya phospholipids as emulsifiers in sodium alginate-formed nanocapsules (NCs), which were further reinforced with acid-processed gelatin by electrostatic adsorption, and then incorporated into hyaluronic acid (HA)-fabricated microneedles (MNs) to construct a new transdermal drug delivery system (HAMNs-CIO@NCs). The obtained CIO-loaded nanocapsules (CIO@NCs) with optimized formulation showed 246.5 ± 4.2 nm in diameter, −24.5 ± 1.7 mV in zeta potential, 22.60% in drug loading, and kept physical stability. In HAMNs-CIO@NCs, the CIO@NCs were homogeneously distributed, and the HAMNs-CIO@NCs with sufficient mechanical hardness were successfully pierced into skin. Compared with the free CIO application, the transdermal fluxes of cinnamaldehyde and cinnamic acid in HAMNs-CIO@NCs group were increased to 8.5 and 6.3 times, and the application was completed within 1 min with no essential oil residue on skin, which improved patient compliance. Further more, HAMNs-CIO@NCs effectively alleviated the symptoms of primary dysmenorrhea in rats and reduced the expression ratio of PGF2α/PGE2 in uterus. This newly designed drug delivery system is formulated with natural food-derived materials, and CIO is served as drug and carrier excipient for self-assembling nanocapsules in a green manufacturing process, thus providing a new strategy for efficiently using essential oils and contributing to a simple and safe treatment for relieving pain of primary dysmenorrhoea.