Macromolecular delivery into skin using a hollow microneedle.

The objective of the present study was to obtain information to develop an effective delivery device regarding a sophisticated hollow microneedle array-patch system. Thus, the potential of hollow microneedles was investigated for enhancing the transdermal delivery of hydrophilic large molecular compounds, and the effect of variable parameters on drug release behavior was determined from skin. Fluorescein isothiocyanate (FITC)-dextrans (4.3 kDa), FD-4, was used as the main model compound, and it was successfully loaded into the lower epidermis as well as the superficial dermis of the skin in hairless rats by a hollow microneedle. The higher the volume of FD-4 solution injected, the faster the FD-4 release rate from skin. In addition, release rate tended to increase when FD-4 was administered dividedly by multiple injections. These release profiles of FD-4 were expressed by Fick's law of diffusion. Furthermore, a combination of the formulation strategy and hollow microneedle-assisted delivery was useful for controlling the drug release rate from skin. Release profiles from drug-loaded skin were also compared by changing the molecular weights of model compounds. The larger molecular size of compounds caused a lower release rate from skin. These results suggest the utilization of hollow microneedle to enhance transdermal delivery of large molecular compounds and provide useful information for designing an effective hollow microneedle system.