TOPICAL DELIVERY OF ANTI-INFLAMMATORY COMPOUNDS 343 Chemical Co., LTD. (Tokyo, Japan). Silicol® 200 (dimethicone) was obtained by Esperis (Milan, Italy). Compritol® 888 ATO (glyceryl behenate, tribehenin), a mixture of mono-, di- and triglycerides of behenic acid (C22), was a gift of Gattefossè (Milan, Italy). Carbopol® Ultrez 20 (acrylates/C10-30 alkyl acrylate crosspolymer) was obtained by The Lubrizol Corporation (Wickliffe, OH). All other materials were of analytical grade. PREPARATION OF DG AND SG FORMULATIONS The composition of emulsions A,C and B,D containing 0.5% of DG and SG, respectively, is reported in Table I. Briefl y, the ingredients of the emulsion oily phase (cetearyl alcohol, Myritol® 318, Silicol® 200, colonial monolaurin, Brij® 721P, Brij® 72, Arlamol® E, Cetiol® SB45) were mixed at 60°C and then slowly added to the water phase (Dermosoft® OMP and water) using a turbomixer and maintaining the temperature of 60°C during the preparation. The water phases of C and D formulations contained 1% of Lecinol® S-10. Final formulations were made viscous by Carbopol® Ultrez 20 and arginine. The composition of gel formulations E,G and F,H containing 0.5% of DG and SG, re- spectively, is reported in Table II. The gel formulations were prepared by dispersing Carbopol® Ultrez 20 in water at 60°C and then adding Dermosoft® OMP, DG and argi- nine with constant stirring. The water phases of G and H formulations contained 1% of Lecinol® S-10. All the formulations were stored at 4°C before use. SLN PREPARATION Blank and drug-loaded SLNs were prepared by ultrasonication (US) method following the procedure reported elsewhere (15). Briefl y, Compritol® 888 ATO (5 g) was melted at Table I Composition of A–D emulsions (% w/w) Trade name INCI name A B C D Cetearyl alcohol Cetearyl alcohol 2.5 2.5 2.5 2.5 Myritol® 318 Caprylic/capric triglyceride 4 4 4 4 Silicol® 200 Dimethicone 1.5 1.5 1.5 1.5 Colonial monolaurin Glyceryl laurate 1.5 1.5 1.5 1.5 Dermosoft® OMP Methylpropandiol, caprylyl glycol, phenylpropanol 2.5 2.5 2.5 2.5 Brij® 721P Steareth-21 2 2 2 2 Brij® 72 Steareth-2 3 3 3 3 Arlamol® E PPG-15 stearyl ether, BHT 4 4 4 4 Arginine Arginine 1 1 1 1 Cetiol® SB45 Butyrospermum parkii 5 5 5 5 Lecinol® S-10 Hydrogenated lecithin — — 1 1 Potassium glycyrrhizinate Potassium glycyrrhizinate 0.5 — 0.5 — Stearyl glycyrrhetinate Stearyl glycyrrhetinate — 0.5 — 0.5 Carbopol® Ultrez 20 Acrylates/C10-30, alkyl acrylate crosspolymer 0.3 0.3 0.3 0.3 Water Aqua 72.2 72.2 71.2 71.2

JOURNAL OF COSMETIC SCIENCE 344 85°C and SG (1 g) was added. The melted lipid phase was dispersed in the hot (85°C) surfactant solution (Pluronic® F68, 1.5 g) by using a high-speed stirrer (UltraTurrax T25 IKA-Werke GmbH & Co. KG, Staufen, Germany) at 8000 rpm. The obtained preemul- sion was ultrasonifi ed by using a UP 400 S (Ultraschallprozessor, Dr. Hielscher GmbH, Teltow, Germany) maintaining the temperature at least 5°C above the lipid melting point. After US method, the obtained dispersion was cooled in an ice bath to solidify the lipid matrix and to form SLNs. To acquire insights about the mechanism involving SG release from SLN, we prepared two different hydrogels (SLN-IN and SLN-OUT) using glycerol and xanthan gum as excipients (12). Briefl y, SLN-IN formulation was produced adding to SG-loaded SLN suspensions (89%, w/w), 10% (w/w) of glycerol, and 1% (w/w) of xanthan gum, whereas SLN-OUT was produced adding to a suspension of not loaded SLN and free SG (89%, w/w), 10 (w/w) of glycerol, and 1% (w/w) of xanthan gum. Hydrogels were stirred at 1000 rpm for 5 min and then stored at 4°C before use. CHARACTERIZATION OF SG-LOADED SLN Particle size distribution. Mean particle size of the lipid dispersions was measured by photon correlation spectroscopy (PCS). A Zetamaster (Malvern Instrument Ltd., Worcs, England), equipped with a solid-state laser having a nominal power of 4.5 mW with a maximum output of 5 mW at 670 nm, was used. Analyses were performed using a 90° scattering angle at 20 ± 0.2°C. Samples were prepared by diluting 10 μl of SLN suspension with 2 ml of deionized water previously fi ltered through a 0.2-μm Acrodisc LC 13 PVDF fi lter (Pall-Gelman Laboratory, Ann Harbor, MI). During the experiment, refractive index of the samples always matched the liquid (toluene) to avoid stray light. Determination of drug loading. The percentage of SG entrapped in the lipid matrix was determined as follows: a fi xed amount of SLN dispersion was fi ltered using a Pellicon XL tangential ultrafi ltration system (Millipore, Milan, Italy) equipped with a polyethersul- fone Biomax 1000 membrane (Millipore) with a 1,000,000 daltons molecular weight cutoff. An amount of retained material was freeze dried, dissolved in dichloromethane, and analyzed by ultraviolet (UV) spectrophotometry at 240 nm (Spectrophotometer Table II Composition of E–H Gel Formulations (% w/w) Trade name INCI name E F G H Dermosoft® OMP Methylpropandiol, caprylyl glycol, phenylpropanol 2.5 2.5 2.5 2.5 Arginine Arginine 1 1 1 1 Lecinol® S-10 Hydrogenated lecithin — — 1 1 Potassium glycyrrhizinate Potassium glycyrrhizinate 0.5 — 0.5 — Stearyl glycyrrhetinate Stearyl glycyrrhetinate — 0.5 — 0.5 Carbopol® Ultrez 20 Acrylates/C10-30 Alkyl acrylate crosspolymer 0.6 0.6 0.6 0.6 Water Aqua 95.4 95.4 94.4 94.4