Formation and Closure of Microchannels in Skin Following Microporation

ABSTRACTPurposeTo characterize the microchannels created in hairless rat skin by microneedles and investigate their closure following exposure to different occlusive conditions.MethodsMaltose microneedles were characterized by scanning electron microscopy. The microchannels created and their closure when exposed to different conditions was investigated using a variety of techniques.ResultsMicroscopic imaging indicates a pyramidal geometry of maltose microneedles with an average length of 559 ± 14 μm and tip radius of 4 μm. Upon insertion into skin, they created microchannels with an average surface diameter of 60 μm and an average depth of 160 ± 20 μm as observed by histological sectioning and confocal microscopy. Skin recovers its barrier function within 3–4 hrs, and microchannels closed within 15 hrs of poration when exposed to environment. However, when occluded, the microchannels remained open for up to 72 hrs in vivo, as observed by calcein imaging, transepidermal water loss measurements and methylene blue staining.ConclusionMaltose microneedles penetrated the stratum corneum barrier and created microchannels in skin which completely close within 15 hrs after poration. However, under occluded conditions, barrier recovery can be delayed for up to 72 hrs in vivo.

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