Development of curcuminoids hydrogel patch using chitosan from various sources as controlled-release matrix.

In this study, we developed the hydrogel patch containing curcuminoids for application in cosmetic purpose. The powder of curcuminoids extracted from rhizome of Curcuma longa Linn. was first formulated into o/w microemulsions before incorporating into the polymer solution. The polymer solutions consisted of chitosan derived from various sources or the blended chitosan starch. We found that chitosan from squid pen gave the patch with highest strength and flexibility. After incorporation of curcuminoids microemulsion into the polymer solution of squid chitosan in ratio of 1 : 1 by weight, values of tensile strength and per cent elongation at break of the obtained patch decreased (from 4.55 +/- 0.41 N mm(-2) to 2.26 +/- 0.01 N mm(-2) for tensile strength and from 40.27 +/- 1.46% to 29.65 +/- 2.77% for elongation at break). The DSC thermogram of the squid patch containing curcuminoids implied non-crystalline structure of polymeric network, corresponding to porous characteristics of the patch surface. The results showed that the curcumin content remained at a concentration of 96% and 40% of the initial content after being kept at 4 degrees C and room temperature, respectively. When the patch was kept at 50 degrees C, the remaining curcumin could not be detected. According to vertical diffusion cell method, we found a rapid rate of curcumin release from the patch. The curcumin release pattern, which fitted well to the Higuchi's model, exhibited two distinct phases: the rapid phase (0-15 min), where the release rate of the curcumin averaged 0.74 microg min(-1) mm(-2), and the slow phase (15-120 min), where the release rate averaged 0.13 microg min(-1) mm(-2). Any sign of skin irritation was not observed in volunteers after single application of the curcuminoids patch in the under-eye area for 30 min. This finding indicates mildness to skin of the developed patch.