Abstract :
A computer-based technique using a 2(k-p) fractional factorial design was applied for screening the factors affecting the effectiveness of recently described multicomponent protective liposomal formulations. These formulations contain sodium ascorbate (vitamin C) as a model drug, sensitive to photochemical oxidation, in free or complexed with α-cyclodextrin form, as well as oil red O, deoxybenzone and oxybenzone as oil soluble light absorbers, incorporated into the lipid bilayer and sulisobenzone as a water soluble light absorber incorporated into the aqueous phase of liposomes. The presence or absence of these four different light absorbers in multilamellar liposomes containing the vitamin in free or complexed with α-cyclodextrin form, and the liposomesʹ preparation method comprised the six factors of the design, each factor being examined in two levels. The vitaminʹs stabilization ratio and percentage entrapment in liposomes were the two response variables to be optimized. The response variables were predicted by multiple regression equations comprising combinations of the six formulation factors. The entrapment values for all the materials were calculated, spectrophotometrically, using second order derivative spectrophotometry. High entrapment values and high protection of sodium ascorbate should characterize the optimum formulation.
