Carbopol 934p

To prepare a formulation of curcumin appropriate for topical administration, 200 mg of carbopol (carbopol 934P; Lubrizol, USA) was added to 2.5 mL of distilled water and 200 mg of curcumin was solubilized in 2 mL of ethanol. The ethanolic dispersion of curcumin and an appropriate amount of ethanol were transferred to an aqueous dispersion of carbopol. Methanol (1.25 mL) was mixed with 1 mL of ethanol and added to the curcumin and carbopol mixture, which was gradually stirred, and carbopol was allowed to soak for 2 h. Triethanolamine (100 mg; Sigma-Aldrich, USA) was added to neutralize the carbopol solution and facilitate the formation of a gel, after which the pH was adjusted to 6.8. The vehicle cream was prepared using the same ingredients and identical methods as the curcumin cream, but curcumin was omitted from the mixture. This topical gel formulation was previously shown to result in the highest permeability of curcumin without causing skin irritation or anti-inflammatory effects [26 (link)]. For topical treatment, curcumin or the vehicle cream (concentration, 200 mg/cm²) was spread on the irradiated skin of pigs twice daily for 35 days, and the first application was performed immediately after irradiation.

Sodium chloride was purchased from Tomita Pharmaceutical Co., Ltd. (Tokushima, Japan). Potassium chloride, calcium chloride, and magnesium chloride were obtained from Duksan Pure Chemicals Co. (Gyeonggi-do, Korea). Lactoperoxidase and glucose oxidase were provided from Biopole (Les Isnes, Belgium) and Amano enzyme Inc. (Nagoya, Japan), respectively. Lactoferrin and lysozyme were purchased from Tatua (Morrinsville, New Zealand) and Dalian Greensnow Egg Products Development Co., Ltd. (Dalian City, People’s Republic of China), respectively. Xylitol and potassium thiocyanate were supplied from Namyung Commercial Co., Ltd. (Seoul, Korea) and Friends Union Enterprises Ltd. (Tianjin, People’s Republic of China), respectively. Carbopol 934P and HEC hhx250 were provided from Lubrizol Corporation (Wickliffe, OH, USA) and Hercules Inc. (Wilmington, DE, USA), respectively. Streptozotocin was purchased from Sigma-Aldrich Chemical Co. (St Louis, MO, USA). All other reagents were of analytical grade and were used without further purification. Double-distilled water was used for all experiments.