Dissolvable layered microneedles with core-shell structures for transdermal drug delivery.

Microneedle (MN) systems for painless transdermal drug delivery have been developed in the past few years to overcome the issues of hypodermic injections. This study introduces a novel dissolvable layered microneedle (LMN) with core-shell structure for efficient transdermal drug delivery. Fabricated by three-step-casting method, the LMNs encapsulated the drug into the HA layer as a "shell", which is supported by PVA layer as core and base. When the LMNs are inserted into the skin, the drug would be released immediately once the HA layer were separated or dissolved. What's more, little drug would be wasted on the residual base after insertion. It is demonstrated that the mechanical property of LMNs is kept well with 100% insertion percentage at 60% relative humidity. Moreover, in the transdermal delivery in vivo test, almost 90% of drug in LMNs could be successful delivered into the skin with 10s, while the homogeneous HA MNs with wide drug distribution need more than 120s to reach the same efficiency. Owing to the advantages of stable mechanical property and rapid efficient drug delivery, the LMNs are more reliable and satisfied for the self-administration in the future.