Gas-propelled microneedles for precision transdermal therapeutics.

Transdermal drug delivery is an appealing approach because it is easy to administer, bypasses first-pass metabolism, and utilizes an extensive surface area of the skin. Microneedles, as an emerging transdermal drug delivery system, offer minimal invasiveness, painlessness, and targeted in-situ treatment. However, the existing microneedle technologies rely on passive diffusion, which can result in unpredictable drug penetration profiles. To enhance the active deep penetration and diffusion of cargoes of the microneedles, gas-propelled microneedles have gradually gained attention from researchers. Gas components can improve transdermal drug delivery efficiency by enhancing drug penetration via pressure effects and bubble generation. Meanwhile, therapeutic gases themselves may function as bioactive components, providing synergistic therapeutic benefits in addition to drug delivery. Hence, Gas-propelled microneedles are promising drug delivery platforms. This review first introduces the structure of the skin and the mechanisms underlying transdermal permeation, followed by a comprehensive overview of recent advances in gas-propelled microneedles for enhancing transdermal drug delivery. We outlined the optimal application strategies based on the distinct properties of different gas-propelled microneedles. It also underscored optimal design strategies for gas-propelled microneedles, assisting formulators in making well-informed decisions. Ultimately, we discussed the current shortcomings of gas-propelled microneedles and future development directions.