Statistical optimization of dithranol-loaded solid lipid nanoparticles using factorial design

This study describes a 3² full factorial experimental design to optimize the formulation of dithranol (DTH) loaded solid lipid nanoparticles (SLN) by the pre-emulsion ultrasonication method. The variables drug: lipid ratio and sonication time were studied at three levels and arranged in a 3² factorial design to study the influence on the response variables particle size and % entrapment efficiency (%EE). From the statistical analysis of data polynomial equations were generated. The particle size and %EE for the 9 batches (R1 to R9) showed a wide variation of 219-348 nm and 51.33- 71.80 %, respectively. The physical characteristics of DTH-loaded SLN were evaluated using a particle size analyzer, differential scanning calorimetry and X-ray diffraction. The results of the optimized formulation showed an average particle size of 219 nm and entrapment efficiency of 69.88 %. Ex-vivo drug penetration using rat skin showed about a 2-fold increase in localization of DTH in skin as compared to the marketed preparation of DTH.