SENSORY ANALYSIS OF A CHITOSAN GEL NANOFORMULATION 313 hydrogel (when comparing to HEC gel in phase I) and no changes occurred after modifi - cations in the gel, the stickiness was considered less important for improving the sensory than the fi lm formation. Regarding the other attributes (spreadability, oiliness), no dif- ferences were found comparing to the basic chitosan hydrogel. Those attributes were not expected to change since the results were considered satisfactory when no differences were detected comparing to the hydroxyethyl cellulose gel. The presence of nanocapsules in the optimized chitosan hydrogel did not lead to higher fi lm formation on the skin, as observed in phase I. This is considered a satisfactory result since the fi lm formation was probably responsible for the low acceptance during phase I, as already mentioned. The nanocapsules, on the other hand, improved the homogeneity of the fi lm formed. Films with greater homogeneity formed on the skin probably induce a more uniform application and a more uniform skin permeation of actives besides a greater skin permanence of the fi lm formed. Another interesting effect of the nanocap- sules could be seen at this point of the study. The nanocapsules decreased the spreadabil- ity and the oiliness of the optimized chitosan gel. This result can be related to changes in the gel network when the adjuvants were added to the chitosan hydrogel. CONCLUSION The chitosan hydrogels were considered innovative and suitable formulations for cosmetic use, with adequate pH, pseudoplastic fl ow, and possibility to incorporate polymeric nanocapsules. Regarding the main questions asked in the introduction section, it was concluded that: (i) For the attributes spreadability, oiliness, and residual stickiness, no signifi cant differences were detected between the chitosan gel and hydroxyethyl cellulose gel. However, the higher im- mediate stickiness and the perception of fi lm formation on the skin, probably led to the low acceptance of this gel, indicating the attributes to be improved. (ii) The addition of adjuvants was essential to turn the gel into a formulation with better sensory properties, demonstrating that the sensory analysis is a suitable tool in the pharmacotechnical development of the novel chitosan hydrogel containing nanoparticles. (iii) For the basic chitosan gel, the nanoparticles increased the perception of residual fi lm on the skin, while for the optimized chitosan gel, the nanocapsules increased the homogeneity of the fi lm formed, without increasing its perception. The work performed showed for the fi rst time the sensory attributes of a chitosan hydrogel for cutaneous use and confi rmed that the nanoparticles may interfere on the sensory attributes of dermatological and cosmetic formulations. ACKNOWLEDGMENTS RVC thanks CNPq/Brazil for her fellowship. The authors thank CNPq/MCTI/Brazil, PRONEX and PRONEM FAPERGS/CNPq, CAPES (Rede Nanotecnologia Farmacêu- tica) for their fi nancial support. REFERENCES (1) C.-C. Lin and A. T. Metters, Hydrogels in controlled release formulations: Network design and math- ematical modeling. Adv. Drug Delivery Rev., 58, 1379–1408 (2006).

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