Focused Review on Metal Nanoparticles in Hair Regeneration and Alopecia: Insights into Mechanisms, Assessment Techniques, Toxicity, Regulatory and Intellectual Property Perspectives

Abstract Hair loss is characterized by a progressive reduction in hair follicle size, decreased hair diameter and length, and alterations in the hair growth cycle, which remains a significant challenge to treat despite the availability of current therapies. Alopecia, lacking a definitive cure, necessitates the development of novel approaches to address hair follicle-related disorders. The application of metal nanoparticles as nanocarriers has emerged as a promising strategy for treating alopecia, gaining considerable attention in recent years. Metal nanoparticles, including iron, zinc, gold, silver, copper, and molybdenum, not only enhance targeted drug delivery to hair follicles but also promote follicular proliferation, maintain scalp hygiene, facilitate wound healing, improve blood circulation, and offer innovative therapeutic solutions for alopecia. Furthermore, these nanoparticles exhibit antioxidant properties and modulate gene expression associated with alopecia, leveraging their dual effects of scavenging reactive oxygen species and remodeling microvasculature. This review comprehensively explores the efficacy of metal nanoparticles and metal chelates in treating alopecia, elucidating their mechanisms in promoting hair regrowth. It also evaluates various experimental methodologies, including permeation studies targeting hair follicles, advanced imaging techniques to assess nanoparticle penetration, in vitro cell line studies, and in vivo animal models. Additionally, the review highlights regulatory considerations, patent landscapes, toxicity profiles, and potential clinical applications of metal nanoparticles in alopecia treatment and hair regeneration. Notably, few articles have provided an integrated analysis covering all these critical aspects, hence making this review a valuable resource for researchers and clinicians seeking innovative solutions for alopecia management. Graphical Abstract