Yadong Wang

Transdermal delivery is an attractive delivery method that increases bioavailability, is suitable for a wide variety of therapeutics, and offers stable delivery outcomes. However, many therapeutics are unable to readily cross the stratum corneum. Microneedles mechanically disrupt the cutaneous barrier to deliver small molecules, proteins, and vaccines. To date, microneedles have not been used in conjunction with coacervate, a liquid–liquid phase separation that protects unstable proteins. A three‐layer microneedle for the controlled release of three different molecules is designed. Through micromolding, microneedles are efficiently generated, which benefits product scalability. The microneedles have good mechanical integrity and effectively penetrate porcine skin ex vivo. The three layers, in the microneedles, release the cargo in a three‐phase manner. The released protein maintains its structure well. Moreover, layer thickness can be controlled by varying fabrication parameters. The microneedles can incorporate both small molecule drugs and protein therapeutics, thus promising uses in multi‐drug therapies through a single treatment.