Substrate-free dissolving microneedles with barbed shape to increase adhesion and drug-delivery efficiency to skin.

Microneedle drug delivery has recently emerged as a clinical method, and dissolving microneedles (DMNs) offer exclusive simplicity and efficiency, compared to the other kinds of microneedles. The tips of most currently available DMNs are cone/house-shaped to result in a lower penetration force. Penetration of the needle tips into the skin relies mainly on the back tape or external pressure, and their adhesion to the skin is relatively low. In addition, only the drug in the part of tips that are pierced into the dermis can be dissolved, resulting in drug waste. Inspired from the barbed structure of the honeybee stinger, we reported substrate-free DMNs with a barbed structure by a dual-molding process, which is suitable for mass production. Those DMNs showed 3-fold greater adhesion force between the needle tips and the skin, better dissolution and deeper penetration than house-shaped DMNs in vivo under the same conditions. For the in situ treatment of psoriasis in mice, the barbed DMNs required only the half dose of house-shaped DMNs to achieve similar efficacy.