Contents lists available at ScienceDirect International Journal of Pharmaceutics journal homepage: www.elsevier.com/locate/ijpharm Nanoemulsion containing 8-methoxypsoralen for topical treatment of dermatoses: Development, characterization and ex vivo permeation in porcine skin Catarina Amorim Oliveira a , Marcos Martins Gouvêa b, ⁎ , Gabriel Ramos Antunes b , Zaida Maria Faria de Freitas c , Flávia Ferreira de Carvalho Marques b , Eduardo Ricci-Junior c a Federal Institute of Education, Science and Technology of Rio de Janeiro – Campus Rio de Janeiro, 20270-021 Rio de Janeiro, RJ, Brazil b Department of Analytical Chemistry – Institute of Chemistry, Fluminense Federal University, 24020-141 Niterói, RJ, Brazil c Department of Drugs and Medicines, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro 21941-972, RJ, Brazil ARTICLE INFO Keywords: 8-Methoxypsoralen Nanoemulsion Formulation characterization Ex vivo permeation HPLC-Fluo ABSTRACT Oral therapy with 8-methoxypsoralen (8-MOP) may cause major side effects, whereas the topical treatment might not be much effective due to the low penetration induced by typical formulations. Therefore, the ob- jectives of this work are the development and characterization of a nanoemulsion (NE) containing 8-MOP to- gether with an ex vivo permeation study, monitored by a validated HPLC-Fluo method, to determine the amount of drug retained in viable skin (epidermis (E) and dermis (D)) and in stratum corneum (SC). The optimized conditions for NE formulation were achieved by full factorial designs (2 5 and 3 2 ): 60 s and 60% of ultrasound time and potency, respectively; 10 mL of final volume; 2% v/v of oil phase (clove essential oil); and 10% m/v of Poloxamer 407. The NE showed mean droplet diameter of 24.98 ± 0.49 nm, polydispersity index (PDI) of 0.091 ± 0.23, pH values of 6.54 ± 0.06, refractive index of 1.3525 ± 0.0001 and apparent viscosity of 51.15 ± 3.66 mPa at 20 °C. Droplets with nanospherical diameters were also observed by transmission electron microscopy (TEM). Ex vivo permeation study showed that 8.5% of the applied 8-MOP dose permeated through the biological membranes, with flux (J) of 1.35 μg cm -2 h -1 . The drug retention in E + D and in SC was 10.15 ± 1.36 and 1.95 ± 0.71 μg cm -2 , respectively. Retention in viable skin induced by the NE was almost two-fold higher than a compounded cream (5.04 ± 0.30 μg cm -2 ). These results suggested that the developed NE is a promising alternative for 8-MOP topical therapy when compared to commercial formulations. 1. Introduction Vitiligo and psoriasis are autoimmune dermatoses that affect up to 5% of the world's population. The immune system of people with these diseases considers the skin cells themselves as pathogens, leading to hypopigmentation due to melanocytes death or appearance of red spots from inflammatory processes (Cohen et al., 2015; Salim et al., 2016). The progression of these dermatoses on the body surface causes social and professional damages, reducing the quality of life and self-esteem of the patients (Taborda et al., 2010). A common therapy for both diseases is the administration of med- icines containing 8-MOP. This substance, also known as methoxsalen or xanthotoxin, is a natural psoralen from the furanocoumarin class and it is characterized by its photosensitizing effect (Santana et al., 2004; Mouli et al., 2013). The light interaction with the drug generates re- active species, making the skin sensitive to radiation. This photo- chemical treatment is commonly called photochemotherapy or PUVA therapy (psoralen + ultraviolet A) (Santana et al., 2004), which is subdivided into systemic PUVA, topical PUVA and PUVA bath (Cestari et al., 2007). Topical PUVA therapy is an easier treatment when compared to PUVA bath. Moreover, it avoids the systemic side effects caused by the oral administration in systemic PUVA therapy. In topical treatments, 8- MOP content is typically 0.1% m/m, incorporated into a variety of https://doi.org/10.1016/j.ijpharm.2018.05.053 Received 10 February 2018; Received in revised form 19 May 2018; Accepted 21 May 2018 ⁎ Corresponding author at: Instituto de Química, Departamento de Química Analítica, Universidade Federal Fluminense, Outeiro São João Batista, s/n, 24020-141 Niterói, Rio de Janeiro, Brazil. E-mail address: mmgouvea@id.uff.br (M.M. Gouvêa). Abbreviations: 8-MOP, 8-methoxypsoralen; ANOVA, Analysis of Variance; CSR, Controlled Shear Rate; DLS, Dynamic Light Scattering; E + D, Epidermis and Dermis; HLB, Hydrophilic- Lipophilic Balance; HPLC, High Performed Liquid Chromatography; ICH, International Conference on Harmonization; LOD, Limit of Detection; LOQ, Limit of Quantification; NE, Nanoemulsion; NLC, Nanostructured Lipid Carriers; SLN, Solid Lipid Nanoparticles; PDI, Polydispersity Index; RSD, Relative Standard Deviation; SD, Standard Deviation; S, Slope; SC, Stratum Corneum; TEM, Transmission Electron Microscopy; PUVA, Psoralen and Ultraviolet A International Journal of Pharmaceutics 547 (2018) 1–9 Available online 22 May 2018 0378-5173/ © 2018 Elsevier B.V. All rights reserved. T