Colloids and Surfaces B: Biointerfaces 143 (2016) 64–70 Contents lists available at ScienceDirect Colloids and Surfaces B: Biointerfaces jo ur nal ho me p ag e: www.elsevier.com/locate/colsurfb Diclofenac acid nanocrystals as an effective strategy to reduce in vivo skin inflammation by improving dermal drug bioavailability Rosa Pireddu a , Carla Caddeo a , Donatella Valenti a , Francesca Marongiu a , Alessandra Scano b , Guido Ennas b , Francesco Lai a,∗ , Anna Maria Fadda a , Chiara Sinico a a Dept. Scienze della Vita e dell’Ambiente, University of Cagliari, via Ospedale 72, 09124 Cagliari, Italy b Dept. Scienze Chimiche e Geologiche, Unita di Ricerca del Consorzio Nazionale di Scienze e Tecnologie dei Materiali (INSTM), University of Cagliari, SS 554 Bivio Sestu, 09042 Monserrato (CA), Italy a r t i c l e i n f o Article history: Received 22 January 2016 Received in revised form 8 March 2016 Accepted 9 March 2016 Available online 14 March 2016 Keywords: Nanosuspension Diclofenac acid Nanocrystals Dermal delivery Skin inflammation Poloxamer 188 a b s t r a c t In this work a diclofenac acid nanosuspension formulation was produced as a novel approach for the treatment of skin inflammation. Drug nanocrystals, prepared by the wet media milling technique and sta- bilized using Poloxamer 188, were characterized by different techniques: scanning electron microscopy, differential scanning calorimetry, X-ray powder diffractometry, Fourier transform infrared spectroscopy and photon correlation spectroscopy. The ability of nanocrystals to improve dermal drug bioavailability was investigated ex vivo by using Franz diffusion vertical cells and mouse skin, in comparison with both diclofenac acid coarse suspensions and a commercial formulation. The topical anti-inflammatory activity of the drug nanosuspension was assessed in vivo by testing its effect compared to common inflamma- tory endpoints: i.e. the inhibition of chemically induced oedema and leucocyte infiltration (reflected in myeloperoxidase activity). Following the milling procedure, diclofenac nanocrystals exhibited a mean diameter of approximately 279 nm, a low polydispersity index (∼0.17) and maintained the same poly- morphic form of the starting bulk powder. When the drug nanosuspension was applied on the mouse skin it produced a higher accumulation of diclofenac in the skin compared to both the coarse suspensions and the commercial formulation, as demonstrated by ex vivo transdermal delivery experiments. Moreover, the nanosuspension provided an in vivo oedema inhibition of 50%, which was not statistically different from the commercial formulation. On the contrary, the nanosuspension showed a higher inhibition of myeloperoxidase activity in the damaged tissue (86%) than the commercial formulation (16%). © 2016 Elsevier B.V. All rights reserved. 1. Introduction Inflammation is an essential protective process to preserve the integrity of the body against physical, chemical and infective agents as well as autoimmune responses. However, the inflammatory response to such attacks may erroneously lead to the damaging of normal tissues, due to an overproduction of reactive oxygen species (ROS), nitric oxide (NO) and cytokines, such as tumor necrosis factor-alpha (TNF-ɑ) [10,19,29]. Therapeutic medication involves the treatment of symptoms by interrupting the inflammatory pro- cess and, if possible, the native cause. Usually, inflammation is localized in a specific organ or apparatus, such as the skin, subcuta- neous tissue, muscular or osteoarticular apparatus, and it can often ∗ Corresponding author at: Università degli Studi di Cagliari, Dipartimento di Scienze della Vita e dell’Ambiente, Via Ospedale 72, Cagliari, 09124, Italy. E-mail address: frlai@unica.it (F. Lai). become chronic. Long-term systemic treatments with steroidal or non-steroidal anti- inflammatory drugs can cause the onset of sev- eral side effects as well as a low drug bioavailability at the site of action [18]. Topical administration may represent a valid alterna- tive to the systemic treatment of local inflamed skin or muscle. In particular, nanosized formulations of anti-inflammatory drugs, which are usually poorly soluble in an aqueous media, can be used to improve the drug’s local bioavailability and efficacy, minimizing the side effects [1]. Nanocrystals can be defined as nanoparticles made of pure drug, with no matrix material, and an average diameter below 1 m (typically in the range of 200–500 nm). They are prepared as a sus- pension (nanosuspension) in a liquid dispersion medium, usually water, stabilized by a suitable surfactant and/or polymer. Nanosus- pensions can be delivered to the local inflamed skin or muscle by various routes of administration, the most common and developed being the oral route [20]. The dermal administration of nanocrystals of poorly soluble actives is a recent application. Indeed, the der- http://dx.doi.org/10.1016/j.colsurfb.2016.03.026 0927-7765/© 2016 Elsevier B.V. All rights reserved.