SENSORY ANALYSIS OF A CHITOSAN GEL NANOFORMULATION 301 was purchased from Degussa (Darmstadt, Germany). To obtain the hydrogels, chitosan (Sigma-Aldrich, São Paulo, Brazil) and hydroxyethyl cellulose (Embacaps, Porto Alegre, Brazil) were used. Also, lactic acid (85%), decamethylcyclopentasiloxane (volatile silicone fl uid—DC 245) and carboxylic pirrolidon acid sodium salt (PCA-Na), obtained from Via Farma (São Paulo, Brazil) were applied. Acetone of analytical grade [Vetec, Rio de Janeiro, Brazil] and MilliQ® water were used in the preparation of the nanocapsules. METHODS Production of polymeric nanocapsule suspension. The nanocapsule aqueous suspension was prepared by means of the interfacial deposition of preformed polymer, through the preparation of two separate phases. An organic phase was obtained by dissolving the polymer Eudragit RS 100® (500 mg) and the capric/caprylic triglycerides (1.65 ml) in acetone (135 ml) at 40°C, under magnetic stirring. An aqueous phase was ob- tained by dissolving polisorbate 80 (380 mg) in ultrapure water (265 ml). The or- ganic phase was then injected into the aqueous phase, by a controlled rate, and the nanocapsules were formed and maintained under stirring for 10 min. The total amount of organic solvent and a partial amount of water were eliminated under re- duced pressure. The fi nal volume was 50 ml and the suspension was then stored at room temperature protected from light. Production of hydrogels containing, or not, polymeric nanocapsules. Hydrophilic gels based on chitosan or hydroxyethyl cellulose were prepared (Table I). For the hydrogels containing nanocapsules, the colloidal suspensions were incorporated in total substitution of the water. The chitosan hydrogels were obtained through the dispersion of the polymer in water or in nanocapsule suspension. Then, lactic acid was added in order to allow the entangle- ment of the chitosan chains, leading to hydrogels. After incorporation of diazolidinyl urea, the hydrogels were well homogenized and stored under room temperature in plastic semisolid fl asks. They were named CH and CH-NC. Table I Hydrogel Components Component CH CH-NC HEC HEC-NC CH-OPT CH-NC-OPT Hidroxyethyl cellulose — — 2% 2% — — Chitosan 2.50% 2.50% — — 2.50% 2.50% Lactic acid 1% 1% — — 1% 1% Silicone DC 245® — — — — 3% 3% PCA-Na — — — — 2% 2% Diazolidinyl urea 0.50% 0.50% 0.50% 0.50% 0.50% 0.50% NC suspension — qsp — qsp — qsp Ultrapure water qsp — qsp — qsp — CH: chitosan gel, HEC: hydroxyethyl cellulose gel, NC: nanocapsules, OPT: optimized hydrogels, PCA-NA: carboxylic pirrolidon acid sodium salt.

JOURNAL OF COSMETIC SCIENCE 302 The hydroxyethyl cellulose hydrogels were obtained through the dispersion of the poly- mer in water or in nanocapsule suspension. The dispersion was stored for 48 h. Then, the hydrogels were well homogenized, added of diazolidinyl urea, and stored under room temperature in plastic semisolid fl asks. They were named HEC and HEC-NC. On the basis of the results of the sensory analysis (phase I), which aimed to determine the attributes that differentiated the chitosan gels from the hydroxyethyl cellulose gels, the chitosan hydrogel was optimized as described on Table I. The hydrogels were prepared as for the prior chitosan gels, in except for the addition of PCA-Na in the water or nanocap- sules suspension, before the gel formation, and the addition of silicone at the fi nal homog- enization process. They were named CH-OPT and CH-NC-OPT. Presence of nanocapsules in the hydrogels. The presence of nanocapsules in the hydrogels ob- tained by addition of nanocapsule aqueous suspension was confi rmed through size distri- bution analysis (laser diffraction) and electron microscopy analysis (transmission electron microscopy [TEM]). For the size distribution analysis, the hydrogels were diluted in ul- trapure water in the sample container at room temperature. The refraction index applied was 1.38, related to Eudragit RS100®, the former of the nanocapsule shell. The results represent an average measurement from three different batches, in a way that the size distribution was measured by volume and by number of particles. For the electron microscopy analysis, the hydrogels were diluted in ultrapure water (1:100 w:v) and placed on formvar-carbon grids (400 mesh, Electron Microscopy Sciences, Hatfi eld, PA), which were stained with uranyl acetate (2% w:v). The TEM equipment (JEM 1200 Exll, Jeol, Tokyo, Japan) was operated at 80 kV. Analysis of the hydrogels pH. The pH values of the formulations were measured in a calibrated potentiometer, after dilution of hydrogels in distilled water (1:10 w/v), immediately after hydrogels production. The results represent an average measurement from three different batches. Analysis of the hydrogels consistence and fl ow. The rheological analysis was performed in a rota- tional viscosimeter (Brookfi eld® LV-DV-II+Pro, spindle SC4-25, Middleboro, MA), at 25°C. Hydroxyethyl cellulose is a nonionic hydrogel-forming polymer of common use, behaving as non-Newtonian fl uid with pseudoplastic character (22). The chitosan hydro- gel was previously described as presenting pseudoplastic behavior as well (9,23). So, the data obtained from rheological viscosimetry were treated according to the Ostwald fl ow model: τ = Kγn, (1) where τ represents the shear rate, γ represents the shear stress, K is the consistence index, and n is the Power Law index. On the basis of this fl ow model, it is possible to obtain the consistence values of the hydrogels, what enables a better comparison between formula- tions. The results represent an average measurement from three different batches. Sensory analysis. The sensory study was conducted through the analysis of the samples by 60 untrained volunteers (pharmacy undergraduate and postgraduate students), aging be- tween 18 and 35 years. The volunteers performed the analysis in rooms with constant temperature and lightning. This study was approved by the ethics on research national committee. After being introduced to the research and signing of the consent term, the volunteers washed their arms up to the elbows, with neutral soap, without any fragrance. Three circles of 51 mm of diameter were drawn. The samples (approximately 0.3 g) were