Nanoemulsions for Topical Skin Delivery: Recent Advances

The stratum corneum provides an immense physiological impediment to the delivery of pharmaceuticals and cosmeceuticals to the skin and often reduces the effectiveness of conventional topical delivery formulations through insolubility, low skin permeability, and active chemical instability. The excellent nanocarrier capacity to bypass barrier impairments arises with nanoemulsions - isotropic, thermodynamically stable colloidal dispersions containing droplet dispersions within the nanometer range (10-200 nm). The aim herein is to have a cumulative understanding of new progress in the formulation and design of topical nanoemulsions. Principles that make nanoemulsions and microemulsions different especially selection of core excipients, strategies in preparation and physical-chemical characterization methods coupled with the penetration mechanisms are highlighted, followed by the diverse applications in skin disorders (psoriasis, acne, wound healing, oncology) with anti-inflammatory effect, as well as in cosmeceutical product for depigmentation of skin pigment targeting melanogenesis route by stabilized actives, such as kojic dipalmitate, arbutin, bakuchiol and multi-targeted system. Developments on hybrid nanoemulgels, pickering nanoemulsions, ionic liquid-based nanoemulsions together with considerations of intoxication, scale-up, and regulatory affairs, are additionally described.