Challenges, Unmet Needs, and Future Directions for Nanocrystals in Dermal Drug Delivery.

Nanocrystals, defined as crystalline particles with dimensions in the nanometer range (<1000 nm), exhibit unique properties that enhance the efficacy of poorly soluble active compounds. This review explores the fundamental aspects of nanocrystals, including their characteristics and various preparation methods, while addressing critical factors that influence their stability and incorporation into final products. A key focus of the review is the advantages offered by nanocrystals in dermal applications. It also highlights their ability to enhance passive diffusion into the skin and facilitate penetration via particle-assisted dermal penetration. Additionally, the review discusses their capacity to penetrate into hair follicles, enabling targeted drug delivery, and their synergistic potential when combined with microneedles, which further enhance the dermal absorption of active compounds. The review also addresses several commercial products that successfully employ nanocrystal technology, showcasing its practical applications. Summary: Nanocrystals with their special properties are an emerging trend for dermal applications, particularly the development of plantCrystals-natural nanocrystals sourced from plant materials-which represent a promising path for future research and formulation strategies. These advancements could lead to more sustainable and effective dermal products.