Microchannels created by sugar and metal microneedles: Characterization by microscopy, macromolecular flux and other techniques

The objective of this study was to investigate the feasibility of using microneedle technology to enhance transcutaneous permeation of human immunoglobulin G (IgG) across hairless rat skin. Microchannels created by maltose and metal (DermaRoller™) microneedles were characterized by techniques such as methylene blue staining, histological examination, and calcein imaging. Methylene blue staining and histological sections of treated skin showed that maltose microneedles and DermaRoller™ breached the skin barrier by creating microchannels in the skin with an average depth of ∼150 µm, as imaged by confocal microscopy. Calcein imaging and pore permeability index values suggested the uniformity of the created pores in microneedle-treated skin. Transdermal studies with IgG indicated a flux rate of 45.96 ng/cm2/h, in vitro, and a Cmax of 7.27 ng/mL, in vivo, for maltose microneedles-treated skin while a flux rate of 353.17 ng/cm2/h, in vitro, and a Cmax of 9.33 ng/mL, in vivo, was achieved for DermaRoller™-treated skin. Transepidermal water loss measurements and methylene blue staining, in vivo, indicated the presence of microchannels for upto 24 h, when occluded. In conclusion, the microchannels created by maltose microneedles and DermaRoller™ resulted in the percutaneous enhancement of a macromolecule, human IgG. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1931-1941, 2010