Transdermal delivery of sinapine thiocyanate by gelatin microspheres and hyaluronic acid microneedles for allergic asthma in guinea pigs

Dissolving microneedles (MNs) are an efficient, safe, and generally painless method for transdermal distribution of poorly permeable medicines. Here, dissolving composite MNs were prepared from sinapine thiocyanate (ST)-loaded gelatin microspheres (GMS) and hyaluronic acid (HA). To immobilize ST in MNs, we used a two-step centrifuging and molding method. When ST-GMS/ST-HA MNs were placed on the skin, they showed extraordinary mechanical strength and dissolved slowly. In vitro, skin implantation ability was assessed with fluorescein isothiocyanate staining, which revealed progressive penetration from the puncture site into deeper tissues. The feasibility of transdermal delivery of ST-GMS/ST-HA MNs in allergic asthma guinea pigs was then determined through in vivo pharmacodynamic and pharmacokinetic tests. The results indicated that ST-GMS/ST-HA MNs, in comparison with the traditional subcutaneous application approach, achieved both high efficiency and continuous release of ST. Therefore, this device is promising for the delivery ST for allergic asthma therapy.