Purpose: Comparison of transcutaneous immunization of ovalbumin (OA) between two-and three-layered dissolving microneedles (MN) in rats. Methods: We prepared 500 μm long two-layered and three-layered dissolving microneedle (2-MN and 3-MN, respectively) arrays from chondroitin sulfate as the base, and OA as the model antigen. The 2-MN containing OA at the acral portion and 3-MN with OA at the second portion were administered to rat skin transcutaneously. As a positive control, OA solution was injected subcutaneously (sc). The OA delivery and diffusion in the rat skin were studied using confocal microscopy with fluorescein-conjugated OA (FL-OA). Results: The formulated positions of OA were 0-155 ± 5 μm for 2-MN and 175 ± 4 – 225 ± 5 μm for 3-MN. The administered doses of OA were 2.2 ± 0.1 μg, 12.0 ± 0.2 μg and 22.0 ± 0.2 μg for 2-MN, 1.8 ± 0.2 μg, 12.6 ± 0.7 μg, and 20.4 ± 0.3 μg for 3-MN, 10 μg, 100 μg and 1000 μg for sc injection. At 4 weeks after the first administration, 3-MN showed about 2.5-7.0 fold and 5.4 fold higher total Ig (G + A + M) antibody than 2-MN and sc injection of the OA solution. Conclusions: The 3-MN, which delivered OA to the epidermis, is a useful drug delivery system for transcutaneous antigen delivery

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