Controlled Release of Cyclosporine via In-Situ Phase Transformation in A Non-Ionic Microemulsion

Abstract

This study reports structural characterization of a liquid crystalline (LC) phase, formed through water driven transition in a nonionic microemulsion (ME). ME was formulated with α-tocopheryl polyethylene glycol succinate (TPGS)-Span 80 (3:1) as surfactant mixture and Captex 300 as oil phase. LC structures were characterized by polarized light microscopy and differential scanning calorimetry. Transition occurred with 19-23% water addition and it was accompanied with; (a) change of isotropic ME to birefringent LC phase, and (b) improvement in the mechanical properties. However, the transition downshifted to 9.8% water level when the oil phase was loaded with 50 mg/ml cyclosporine. LC structures remained stable at physiological temperature until 72 h and offered controlled release of cyclosporine under artificial sink conditions. We suggest that in situ development of LC phase can be explored to clear long-residing intra-muscular depots capable of discharging the payload at a controlled rate.