JOURNAL OF COSMETIC SCIENCE 60 terms of antioxidant activity. The antioxidant activity of F27 nanogel was found to be low compared with both vitamin C (10 μg/mL) and other vitamin C–loaded nanogels. STABILITY S TUDIES OF FORMULATIONS The formula tions selected optimally for stability studies were placed in two different conditions in the stability chamber containing 60% relative humidity at room tempera- ture at 25°C and 75% relative humidity at 40°C at certain time intervals (15 d, 1, 2, 3, and 6 mo). Selected formulations were stable, and there was no serious change in physical properties during 6 mo (data not shown). CONCLUSION Be cause nanog el-based materials have high drug loading capacity, biocompatibility, stabil- ity, and biodegradability, which are the key points to design a topical drug delivery system, in our study, nanogels were used to develop a formulation, which overcame the stability and absorption problems of vitamin C. And nanogels were successfully prepared by physical self-formation with the polymers, BSA, and CS by a simple green self-assembly technique. The results of in vitro characterization and the antioxidant activity studies were proved that vitamin C–loaded nanogels including CS:BSA with a 1:4 ratio (F19 formulation) presented optimum properties in terms of entrapping vitamin C, formulation homogeneity, pH, viscosity, rheological properties, zeta potential, PI, particle size, in vitro dissolution, and cell culture studies. In light of this study, a stable and an applicable topical nanogel of vitamin C was prepared, and it is promising for clinical studies for antiaging purposes. Figure 5. In vitro antioxidant activity of nanogels. ap 0.05 versus 1 mg vitamin C, F1, F9, F19, F27, and F31, bp 0.05 versus other groups, cp 0.05 versus 10 μg vitamin C, 1 mg vitamin C, F1, F9 F27, and F31, dp 0.05 versus 10 μg vitamin C, 1 mg vitamin C, F1, F9, F19, and F31.

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