Using\nOscillation to Improve the Insertion Depth and\nConsistency of Hollow Microneedles for Transdermal Insulin Delivery\nwith Mechanistic Insights

Microneedles (MNs)\noffer the potential for discrete and painless\ntransdermal drug delivery, yet poor insertion and dosing consistency\nhave hindered their clinical translation. Specifically, hollow MNs\nare appropriate for the administration of liquid modalities, including\ninsulin, which could prove to be beneficial for patients with type\n1 diabetes mellitus. This work aimed to design and manufacture a hollow\nMN with an improved insertion and delivery profile suitable for insulin\nadministration. <i>Ex vivo</i> insertion studies demonstrated\nthat oscillation of MNs upon insertion into skin produced a favorable\ninsertion profile, with reduced variation, compared to static MN insertion.\nHistological staining showed that this could be due to the repeated\nmotion of the oscillating MN disrupting elastic fibers in the dermis.\nAdditionally, permeation studies demonstrated that increased quantities\nof insulin were able to permeate the skin when oscillation was employed\ncompared to static MN insertion. This study has shown that oscillation\nis a valuable tool in improving the transdermal delivery of insulin\nvia a single hollow MN <i>in vitro</i>. Moving forward, <i>in vivo</i> studies should be completed to gain a fuller understanding\nof the benefits of the oscillation of MNs on transdermal drug delivery.