Sulfasalazine (SSZ) has been recommended for rheumatoid arthritis, ulcerative colitis, and Crohn's disease. However, low aqueous solubility and reduced bioavailability obstruct its clinical application. The aim of this study was to formulate a mixed micelles (MM) system composed of two biocompatible copolymers Soluplus and Pluronic F127 to improve the solubility and oral bioavailability of insoluble drug SSZ. SSZ-MM was prepared by an ethanol solvent evaporation method and optimized using 32 factorial designs with respect to quantity of polymers. The average size, zeta potential and entrapment efficiency of the optimized formulation were found to be 59.12 nm, -16.4 mV and 62.04% respectively. The SSZ-MM showed sustained release up to 24 h in in-vitro release study. Ex-vivo endocytic uptake studies revealed involvement of endocytic pathways in the uptake of mixed micelles from the intestine. The in-vivo oral bioavailability study in Wistar rats showed 2.19 folds higher AUC of SSZ-MM than free SSZ, indicating the mixed micelles of Soluplus and Pluronic F127 is a feasible drug delivery system to promote insoluble drug oral absorption in the gastrointestinal tract.
