Pyramid-shaped tips based polymer microneedles for transdermal drug or nanoparticle delivery

This paper reports on polymer solid microneedles with pyramid-shaped tips and titanium shields for transdermal transportation of drug molecules, bio-macromolecules, or nano-particles. Microelectromechanical system (MEMS) techniques, such as masking, etching, alignment, development, sputtering, were adapted to produce polymer microneedles with sharp tips to reduce the force to pierce into skin. Polymer microneedle piecing testing and methylene blue dye experiment revealed that microneedles had enough mechanical stability to destroy the aluminium foils and corneums of mouse ventral skin. Finally, arrays of polymer microneedles were proven to increase permeability of vitro and vivo mice ventral skins to a macromolecular protein, human serum albumin (HSA) and DNA vaccine, by up to three orders of magnitude. In all, the polymer microneedles can be successfully fabricated with an appropriate geometry and sufficient strength to dramatically increase transdermal drug delivery or nanoparticle transportation.