Microneedles for Enhanced Topical Treatment of Skin Disorders: Applications, Challenges, and Prospects

Microneedles (MNs) can be used for the topical treatment of skin disorders as they directly deliver therapeutics to the site of skin lesions, resulting in increased therapeutic efficacy while having minimum side effects. MNs are used to deliver different kinds of therapeutics (e.g., small molecules, macromolecules, nanomedicines, living cells, bacteria, and exosomes) for treating various skin disorders, including superficial tumors, wounds, skin infections, inflammatory skin diseases, and abnormal skin appearance. The therapeutic efficacy of MNs can be improved by integrating the advantages of multiple therapeutics to perform combination therapy. Through careful designing, MNs can be further modified with biomimetic structures for the responsive drug release from internal and external stimuli and to enhance the transdermal delivery efficiency for robust therapeutic outcomes. Some studies have proposed the use of drug-free MNs as a promising mechanotherapeutic strategy to promote wound healing, scar removal, and hair regeneration via a mechanical communication pathway. Although MNs have several advantages, the practical application of MNs suffers from problems related to industrial manufacture and clinical evaluation, making it difficult for clinical translation. In this study, we summarized the various applications, emerging challenges, and developmental prospects of MNs in skin disorders to provide information on ways to advance clinical translation.