Background: Cannabidiol (CBD), a non-psychoactive compound derived from Cannabis sativa, exhibits therapeutic potential for various conditions, including inflammation, pain, and skin disorders, making it a promising candidate for the topical treatment of psoriasis. However, its poor water solubility and instability limit its therapeutic efficacy. This study focuses on the development and characterization of CBD-loaded nanoemulsions using argan oil as the lipid phase, with and without a chitosan coating, which serves as a stabilizing and functional biopolymer. Methods: Nanoemulsions (NE) and chitosan-stabilized nanoemulsions (CS-NE), both without CBD (serving as controls), and CBD-loaded variants (CBD-NE and CBD-CS-NE) were prepared and characterized for their physicochemical properties, including pH, droplet size, polydispersity index (PDI), zeta potential (ζ-potential), and viscosity at various shear rates and temperatures. Stability was assessed over time, and drug release behavior was investigated through in vitro diffusion and ex vivo skin permeation studies, followed by kinetic modeling. Safety was evaluated through in vitro cytotoxicity assays using HaCaT keratinocyte cells, as well as in vivo toxicity studies using Caenorhabditis elegans (C. elegans). Results: The chitosan-coated formulations exhibited enhanced physical stability, nanoscale droplet size, a positive surface charge, and increased viscosity. Release studies demonstrated that CBD-CS-NE enabled controlled and sustained drug release, with a strong correlation to the Higuchi model, indicating diffusion-controlled permeation. Cytotoxicity assays indicated that CBD-CS-NE was non-toxic to cultured cells, while in vivo testing with C. elegans revealed sensitivity to chitosan-coated systems. Conclusions: These findings highlight the potential of CBD-loaded argan oil nanoemulsions, particularly those stabilized with chitosan, as potential topical delivery systems for managing psoriasis.

Homocystinuria type CblC is a congenital error in cobalamin metabolism characterized by increased homocysteine and methylmalonic acid levels, together with a reduced methionine availability. This metabolic imbalance leads to multisystemic pathologies, including ophthalmic pathologies that cause damage to the photoreceptors and oculomotor disorders, such as pigmentary retinopathy and nystagmus, respectively. Current commercial treatment (Megamilbedoce^®) is mainly based on intramuscular hydroxocobalamin administration. Although this approach may improve systemic manifestations, it is ineffective at the ophthalmic level. Given the ophthalmic complications, there is a clear need for new therapeutic strategies capable of significantly reaching the eyeball, improving visual function and patient quality of life. The most convenient and acceptable route for patients is topical–ophthalmic administration. However, treatments administered by this route have significant limitations due to anatomical and physiological ophthalmic barriers. In this context, advanced ophthalmic drug delivery systems have gained increasing interest as strategies to address the low ocular bioavailability of conventional treatments. By increasing ocular residence time, limiting drug loss through tear turnover and nasolacrimal drainage, and improving interaction with ocular tissues, these platforms may enhance local drug availability and therapeutic performance. Nanoparticles, lipid-based carriers, hydrogels, in situ gelling systems, surfactant-based formulations and other multifunctional delivery approaches have shown potential to improve drug retention, tissue penetration and controlled release within the ocular environment. Although reaching posterior ocular tissues through topical administration remains a major pharmacological challenge, these technologies open new possibilities for developing less invasive and more effective treatments for the ocular manifestations of CblC-type homocystinuria.