title: Two-photon polymerization of microneedles for transdermal drug delivery.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: University of North Carolina Chapel Hill and North Carolina State University, Joint Department of Biomedical Engineering, CB 7115, 2147 Burlington Labs, Raleigh, NC 27695, USA.
authors.forename: Shaun D
authors.initials: SD
authors.lastname: Gittard
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Ovsianikov
authors.forename: Boris N
authors.initials: BN
authors.lastname: Chichkov
authors.forename: Anand
authors.initials: A
authors.lastname: Doraiswamy
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Narayan
mesh_terms: D000279:Administration, Cutaneous; D001672:Biocompatible Materials; D016503:Drug Delivery Systems / Q000295:instrumentation*; D006801:Humans; D055616:Microtechnology / Q000379:methods*; D009339:Needles; D004364:Pharmaceutical Preparations / Q000008:administration & dosage*
chemical_list: D001672:Biocompatible Materials; D004364:Pharmaceutical Preparations