The purpose of this work is to characterize microchannels created by polymeric microneedles, applied by hand, and to demonstrate enhanced delivery of topically applied formulations of lidocaine hydrochloride and methylprednisolone sodium succinate (MPSS). 3M's Microstructured Transdermal System (MTS) arrays were applied to domestic swine to demonstrate reliability of penetration, depth of penetration and durability of the structures to repeat application and high force. Tissue levels of lidocaine and MPSS following topical application with and without microneedle pretreatment were determined by HPLC-MS analysis following digestion of biopsies. Almost all microneedles penetrate the stratum corneum upon hand force application. The depth of penetration varies from <100µm to nearly 150µm depending on the application force and the firmness of the underlying tissue. The arrays show excellent durability to repeated in-vivo application, with less than 5% of the structures evidencing even minimal tip bending after 16 applications. Under extreme force against a rigid surface, the microneedles bend but do not break. A lidocaine hydrochloride formulation applied topically in-vivo showed ~340% increase in local tissue levels when the MTS arrays were used to twice pre-treat the skin prior to applying the drug. Local delivery of a topically applied formulation of MPSS was over one order of magnitude higher when the application site was twice pre-treated with the MTS array. 3M's MTS array (marketed as 3M(TM) Microchannel Skin System) provides repeatable and robust penetration of the stratum corneum and epidermis and enhances delivery of some formulations such as lidocaine hydrochloride.

The detection and localization of iodine in biological tissues have traditionally presented problems associated with sample preparation of soluble elements. Standard sample preparation for biological tissue involves methods which solubilize or extract iodine.Furthermore, analytical methods for detection of elements typically have been studied in smooth flat materials. We describe two methods using frozen pig skin for detecting iodine in tissue, creating digital color maps of iodine concentrations in cross sections of pig skin, and visualizing flow properties of an iodine-releasing coating at skin surfaces.Biological samples were analyzed with the Philips XL30 SEM integrated EDAX systems using peak identification and digital color mapping software packages. Iodine-releasing coatings were applied to pig skin explants and processed by freeze-drying. The stratum corneum and hair follicle regions of pig skin remained undistorted and identifiable after dissection and processing. Iodine was detected in the coating, in the stratum corneum, and in the tissue surrounding hair follicles (Fig. 1).