Two-photon polymerization of microneedles for transdermal drug delivery.

IMPORTANCE OF THE FIELD: Microneedles are small-scale devices that are finding use for transdermal delivery of protein-based pharmacologic agents and nucleic acid-based pharmacologic agents; however, microneedles prepared using conventional microelectronics-based technologies have several shortcomings, which have limited translation of these devices into widespread clinical use. AREAS COVERED IN THIS REVIEW: Two-photon polymerization is a laser-based rapid prototyping technique that has been used recently for direct fabrication of hollow microneedles with a wide variety of geometries. In addition, an indirect rapid prototyping method that involves two-photon polymerization and polydimethyl siloxane micromolding has been used for fabrication of solid microneedles with exceptional mechanical properties. WHAT THE READER WILL GAIN: In this review, the use of two-photon polymerization for fabricating in-plane and out-of-plane hollow microneedle arrays is described. The use of two-photon polymerization-micromolding for fabrication of solid microneedles is also reviewed. In addition, fabrication of microneedles with antimicrobial properties is discussed; antimicrobial microneedles may reduce the risk of infection associated with the formation of channels through the stratum corneum. TAKE HOME MESSAGE: It is anticipated that the use of two-photon polymerization as well as two-photon polymerization-micromolding for fabrication of microneedles and other microstructured drug delivery devices will increase over the coming years.