Effect of lyophilization process on the physical properties and stability of tanshinone IIA microemulsions

Tanshinone IIA microemulsions were successfully prepared by freeze-drying method. Annealing was involved in the freeze-drying process, and the effects of lyophilization process on the physical properties including particle size, surface tension, glass transition temperature, and X-ray diffraction pattern were studied. The lyophilized samples were slightly superior to those untreated with lyophilization in terms of surface properties. Moreover, the physical stabilities of tanshinone IIA microemulsions related to insoluble particles and cloud point thermodynamic were also investigated. The lyophilized samples with annealing showed better physical stabilities than those not lyophilized or lyophilized without annealing.