In vivo, in situ and ex vivo comparison of porcine skin for microprojection array penetration depth, delivery efficiency and elastic modulus assessment

Jonathan C. J. Wei, Ian D. Cartmill, Mark Anthony Fernance Kendall, Michael Crichton

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Abstract

With the development of wearable technologies, the interfacial properties of skin and devices have become much more important. For research and development purposes, porcine skin is often used to evaluate device performance, but the differences between in vivo, in situ and ex vivo porcine skin mechanical properties can potentially misdirect investigators during the development of their technology. In this study, we investigated the significant changes to mechanical properties with and without perfusion (in vivo versus in vitro tissue). The device focus for this study was a skin-targeting Nanopatch vaccine microneedle device, employed to assess the variance to key skin engagement parameters – penetration depth and delivery efficiency – due to different tissue conditions. The patches were coated with fluorescent or 14C radiolabelled formulations for penetration depth and delivery efficiency quantification in vivo, and at time points up to 4 h post mortem. An immediate cessation of blood circulation saw mean microneedle penetration depth fell from ∼100 μm to ∼55 μm (∼45%). Stiffening of underlying tissues as a result of rigor mortis then augmented the penetration depths at the 4 h timepoint back to ∼100 μm, insignificantly different (p = 0.0595) when compared with in vivo. The highest delivery efficiency of formulation into the skin (dose measured in the skin excluding leftover dose on skin and patch surfaces) was also observed at this time point of ∼25%, up from ∼2% in vivo. Data obtained herein progresses medical device development, highlighting the need to consider the state and muscle tissues when evaluating prototypes on cadavers.
Original languageEnglish
Article number105187
JournalJournal of the Mechanical Behavior of Biomedical Materials
Volume130
Early online date25 Mar 2022
DOIs
Publication statusPublished - Jun 2022

Keywords

  • Elastic modulus
  • Histology
  • Medical device
  • Microneedles
  • Skin
  • Soft tissue biomechanics

ASJC Scopus subject areas

  • Mechanics of Materials
  • Biomedical Engineering
  • Biomaterials

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