Stratum corneum, the protective barrier of the skin, is the principal obstacle for drugs to pass through the skin, especially macromolecular drugs or hydrophilic drugs. Micron-sized microneedles in transdermal drug delivery system can permeabilize the stratum corneum to promote the penetration of skin-impermeant drugs by creating reversible microchannels in the skin in a minimally invasive manner, which can overcome low permeability of traditional transdermal drug delivery system. What's more, percutaneous microneedle insertion can cause less or even no pain because it has limited insertion depth without touching nerves in the skin. Polymeric microneedles not only have sufficient strength to puncture the stratum corneum but also exhibit other outstanding performances such as biocompatibility and relatively lager drug loading capacity. It is safe even if polymeric microneedles rupture in the skin. Polymeric microneedles have so many advantages that they have an extensive prospect in transdermal drug delivery system, which has received abroad attention. In this paper, the recent advances of polymeric microneedles are reviewed in detail from the following aspects:microneedle types, manufacturing methods, and applications in transdermal drug delivery system. Challenges and prospects of polymeric microneedles are also discussed.
Contents
1 Introduction
2 Types of polymeric microneedles
3 Manufacturing methods of polymeric microneedles
4 Applications of polymeric microneedles in transdermal drug delivery system
4.1 Rapid drug release
4.2 Extended drug release
4.3 Stimuli-responsive drug release
5 Conclusion and outlook