Importance of skin biophysical properties relevant to microneedle insertion

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Compiling data on the skin microanatomy was interesting since they provide the basis for the microneedle development for both drug delivery and disease diagnosis. My review not only show why it is paramount to catalogue skin thicknesses from various part of bodies (also from various species used in academia/industry), but also understanding the skin microstructures that provides the biomechanical features. Multiple studies have already showed that microneedles are painless compared to hypodermic needles. The most important characteristic of microneedle technology is its ability to pierce the stratum corneum without breaking or buckling during insertion. Therefore, µNDs designed with an appropriate geometry is not only utmost importance to achieving a successful skin insertion, but also dictates the amount of drug that can be incorporated and rate of its release within the skin. Our understanding of the thickness of the different layers of the skin has increased tremendously in past decade encouraging the development of more advanced µNDs platforms. However, there is further need for investigating the effect of various diseases and pathological conditions on the thickness of various skin layers and their biomechanical properties including viscoelastic behaviour. This knowledge will be crucial in not only designing the future generation of µNDs, but also the applicators personalised for the skin and disease type. More than anything else, and if nothing else, I hope this article sheds some light on the interplay between skin biomechanics and microneedles.

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