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Skin-targeted drug delivery is broadly employed for both local and systemic therapeutics and is an important tool for discovery efforts in cutaneous biology. Recently, emerging technologies support efforts toward skin-targeted biocargo delivery for local and systemic therapeutic benefit. Effective targeting of bioactive molecules, including large (molecular weight > 500 Da) or complex (hydrophilic and charged) molecules, to defined cutaneous microenvironments is intrinsically challenging owing to the protective barrier function of the skin. Dissolvable microneedle arrays (MNAs) have proven to be a promising technology to address the unmet need for controlled, minimally invasive, and reliable delivery of a wide range of biocargos to the skin. In this paper, we describe the unique properties of the skin that make it an attractive target for vaccine delivery, for immune-modulating therapies, and for systemic drug delivery and the structural characteristics of the skin that present obstacles to efficient intracutaneous and transdermal delivery of bioactive molecules. We provide an overview of MNA fabrication and the characteristics and mechanisms of dissolvable MNA cargo delivery to the cutaneous microenvironment. We present a representative example of a clinical application of MNAs and discuss future directions for MNA development and applications., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Systemically delivered targeted biologics have revolutionized the treatment of moderate-to-severe psoriasis. For milder forms of psoriasis, topical therapies, primarily corticosteroids, remain the mainstay of treatment to reduce the risks and off-target side effects associated with systemic therapies. Most newly developed biologics, including monoclonal antibodies, are structurally complex and are unable to penetrate the skin barrier. Recently developed liposomal spherical nucleic acids overcome this barrier and enable topical delivery of antisense oligonucleotides capable of specifically targeting inflammatory pathways underlying psoriasis pathogenesis., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)