Effect of Cholesterol to Vitamin D3 and Span 60 to Tween 60 Ratios on the Characteristics of Niosomes: Variable Optimization Using Response Surface Methodology (RSM)

The main objective of this research was to evaluate the partial replacement of cholesterol (CSL) with vitamin D3 (VD3) on the niosome structure. The effects of different molar ratios of Span 60 (SP60) : Tween 60 (TW60) and CSL : VD3 were investigated on the physicochemical characteristics of niosomes, including particle size, span (distribution width), stability, and encapsulation efficiency of VD3. The data were then optimized using response surface methodology (RSM). Larger particles were obtained as the ratios of SP60 : TW60 and CSL : VD3 were increased. The smallest particles were obtained at SP60 : TW60 and CSL : VD3 ratios of 40.46 : 59.54 and 38.06 : 61.94, respectively. Increasing the ratio of SP60 : TW60 led to higher values of span. As CSL : VD3 ratio was increased from 0 : 100 to 67.67 : 32.32, value of the span was decreased; however, increasing this ratio further led to the increased value of the span. The lowest values of the span were observed at SP60 : TW60 and CSL : VD3 ratios of 67.90 : 32.10 and 72.41 : 27.59, respectively. The increase in the SP60 : TW60 ratio led to lower values of encapsulation efficiency. The highest values for encapsulation efficiency were observed at ratios of 31.76 : 68.24 and 40.02 : 59.98 for SP60 : TW60 and CSL : VD3, respectively. The highest stability was observed at SP60 : TW60 and CSL : VD3 ratios of 31.72 : 68.28 and 14.65 : 85.35, respectively. The optimum conditions were achieved at ratios of 31.72 : 68.28 and 49.37 : 50.63 for SP60 : TW60 and CSL : VD3, respectively. Finally, it can be concluded that VD3 is a suitable replacement for CSL in terms of stability and encapsulation efficiency of niosome.