Roxithromycin-loaded lipid nanoparticles for follicular targeting Hanna Wosicka-Fra ˛ckowiak a , Krzysztof Cal b, *, Justyna Stefanowska b , Eliza Glówka a , Magdalena Nowacka c , Wiktoria Struck-Lewicka d , Biljana Govedarica e , Monika Pasikowska f , Renata De ˛bowska f , Teofil Jesionowski c , Stane Sr9 ci9 c e , Michal Jan Markuszewski d a Department of Pharmaceutical Technology, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Pozna n, Poland b Department of Pharmaceutical Technology, Medical University of Gdansk, Hallera 107, 80-416 Gda nsk, Poland c Institute of Chemical Technology and Engineering, Poznan University of Technology, Berdychowo 4, 60-695 Pozna n, Poland d Department of Biopharmaceutics and Pharmacodynamics, Medical University of Gdansk, Hallera 107, 80-416 Gda nsk, Poland e Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Ljubljana, Ašker9 ceva 7, SI-1000 Ljubljana, Slovenia f Dr Irena Eris Centre for Science and Research, Pulawska 107 A, 02-595 Warsaw, Poland A R T I C L E I N F O Article history: Received 29 June 2015 Received in revised form 27 September 2015 Accepted 30 September 2015 Available online xxx Keywords: Hair follicles Roxithromycin Lipid nanoparticles Ex vivo skin penetration In vivo skin penetration Differential stripping A B S T R A C T Particulate drug carriers e.g. nanoparticles (NPs) have been shown to penetrate and accumulate preferentially in skin hair follicles creating high local concentration of a drug. In order to develop such a follicle targeting system we obtained and characterized solid lipid nanoparticles (SLN) loaded with roxithromycin (ROX). The mean particle size (172  2 nm), polydisperisty index (0.237  0.007), zeta potential (31.68  3.10 mV) and incorporation efficiency (82.1  3.0%) were measured. The long term stability of ROX-loaded SLN suspensions was proved up to 26 weeks. In vitro drug release study was performed using apparatus 4 dialysis adapters. Skin irritation test conducted using the EpiDerm TM tissue model demonstrated no irritation potential for ROX-loaded SLN. Ex vivo human skin penetration studies, employing rhodamine B hexyl ester perchlorate (RBHE) as a fluorescent dye to label the particles, revealed fluorescence deep in the skin, specifically around the hair follicles up to over 1 mm depth. The comparison of fluorescence intensities after application of RBHE solution and RBHE-labelled ROX-loaded SLN was done. Then cyanoacrylate follicular biopsies were obtained in vivo and analyzed for ROX content, proving the possibility of penetration to human pilosebaceous units and delivering ROX by using SLN with the size below 200 nm. ã 2015 Elsevier B.V. All rights reserved. 1. Introduction Follicular penetration of active substances applied topically has for years been undervalued because of the minute area that hair follicles occupy compared to the skin area of the entire body. However, there are body areas where hair density is high enough for the follicles to offer a major drug penetration path, or for the targeted delivery to the specific sites in the follicle. The hair follicle density and the volume of the follicular openings on the forehead and head are the highest on the human body. The combined area of the follicular openings in these locations can be as much as 10% of the total skin area in these body regions. The same body sites frequently suffer from dermatological disorders such as androgen- ic hair loss and common acne, the etiology of which is closely related to the pilosebaceous apparatus. In such cases targeted drug delivery to the hair follicles becomes the key element of the therapy (Blume-Peytavi and Vogt, 2011; Knorr et al., 2009; Wosicka and Cal, 2010). The pilosebaceous unit is a complex structure that includes the hair follicle, hair shaft, adjoining arrector pili muscle and associated sebaceous gland(s) (Fig. 1). Pilosebaceous units can be utilized as reservoirs for localized therapy or as a transport pathway for systemic drug delivery. Various attempts to increase the distribution of active pharma- ceutical ingredient (API) in that region have already been made for such active substances as adapalene, erythromycin–zinc com- plexes, isotretinoin, anti-androgens, diphencyprone and minoxidil (Aljuffali et al., 2014; Morgen et al., 2011; Patzelt et al., 2011; Tschan et al., 1997). Preferential follicular deposition is highly dependent on a type of the vehicle used in the formulation, application way and physicochemical properties of the drug itself. What is even more important this transport pathway especially favors particu- late drug carriers e.g. nanoparticles (NPs) (Glówka et al., 2014; * Corresponding author. Fax: +58 349 10 90. E-mail address: kcal@wp.pl (K. Cal). http://dx.doi.org/10.1016/j.ijpharm.2015.09.068 0378-5173/ ã 2015 Elsevier B.V. All rights reserved. International Journal of Pharmaceutics 495 (2015) 807–815 Contents lists available at ScienceDirect International Journal of Pharmaceutics journal homepage: www.elsev ier.com/locate /ijpharm