Nanoscale Res Lett (2010) 5:224–230 DOI 10.1007/s11671-009-9469-5 N A N O E X P R E S S Preparation and Characterization of a Lecithin Nanoemulsion as a Topical Delivery System Huafeng Zhou • Yang Yue • Guanlan Liu • Yan Li • Jing Zhang • Qiu Gong • Zemin Yan • Mingxing Duan Received: 16 July 2009 / Accepted: 14 October 2009 / Published online: 29 October 2009 to the authors 2009 Abstract Purpose of this study was to establish a lecithin nanoemulsion (LNE) without any synthetic surfactant as a topical delivery vehicle and to evaluate its topical delivery potential by the following factors: particle size, morphol- ogy, viscosity, stability, skin hydration and skin penetra- tion. Experimental results demonstrated that an increasing concentration of soybean lecithin and glycerol resulted in a smaller size LNE droplet and increasing viscosity, respectively. The droplet size of optimized LNE, with the glycerol concentration above 75% (w/w), changed from 92 (F10) to 58 nm (F14). Additionally, LNE, incorporated into o/w cream, improved the skin hydration capacity of the cream signiﬁcantly with about 2.5-fold increase when the concentration of LNE reached 10%. LNE was also demonstrated to improve the penetrability of Nile red (NR) dye into the dermis layer, when an o/w cream, incorporated with NR-loaded LNE, applied on the abdominal skin of rat in vivo. Speciﬁcally, the arbitrary unit (ABU) of ﬂuores- cence in the dermis layer that had received the cream with a NR-loaded LNE was about 9.9-fold higher than the cream with a NR-loaded general emulsion (GE). These observa- tions suggest that LNE could be used as a promising topical delivery vehicle for lipophilic compounds. H. Zhou Y. Yue G. Liu Y. Li J. Zhang Q. Gong M. Duan (&) State-Key Laboratory of Biomembrane and Membrane, Biotechnology, School of Life Sciences, Tsinghua University, 100084 Beijing, China e-mail: duanmx@mail.tsinghua.edu.cn H. Zhou e-mail: zhfforever@yahoo.com.cn H. Zhou Z. Yan Jiangsu Longliqi Bioscience Co., Ltd., 215555 Suzhou, China 123 Keywords Lecithin Nanoemulsion Fluorescence Topical delivery system Skin hydration Introduction Topical delivery systems (TDS) have received increased attention during the past few years. TDS could avoid a variety of disadvantages compared with the oral adminis- tration including drastic pH changes, deleterious presence of food and enzymes and ﬁrst-pass effect of the liver. TDS also eschewed injection inconvenience and needle phobia. In addition, TDS were noninvasive and can be self- administered with the minimization of side-effects in the topical drug therapy. However, the paucity of candidates for TDS was presented in the market because few mole- cules yielded skin permeability coefﬁcients sufﬁciently high to meet the clinical therapeutic needs, and TDS was even less applicable for large hydrophilic molecules because of their very low skin permeation rates. The con- tinuous stratum corneum (the outer layer of skin) provided a major barricade for drug penetration to the deeper skin layers and was therefore the usual target for attempts to strength topical drug permeation ability [1–5]. Various kinds of vesicular carriers had been suggested as topical delivery vehicles, including liposomes, micro- emulsions and lipid nanoparticles [6–10]. However, lipo- some formulations had certain limitations such as drug loading and stability. Microemulsions, which consisted of synthetic surfactant, oil, water and co-surfactant, exhibited a lower drug-loading capacity relative to the high con- centration of surfactant, which had been generally acknowledged to induce skin irritation [11, 12]. Recently, due to advantages such as a controlled droplet size, lower concentration of surfactant and the ability to efﬁciently