Stability and Rheological Characteristics of Baicalin Loaded in Microemulsion-based Gel

OBJECTIVE To study the stability and rheological characteristics of baicalin loaded in microemulsion-based gel(B-MBG). METHODS Preliminary stability test was used to study the appearance properties, micromorphology, pH, viscosity, content and particle size of B-MBG. The rheology test was utilized to study the steady-state and dynamic rheological properties of B-MBG. The influencing factor test was used to study the pH, viscosity, content and particle size changes of B-MBG on 0, 5, 10, 15, 20 and 30 d, in high temperature, low temperature, high humidity and light conditions. RESULTS Preliminary stability test showed that B-MBG was yellow, clear and transparent, with uniform texture and obvious Tyndall effect. The pH was 5.12±0.02, the mean particle size was (14.95±0.04)nm and polymer dispersity index was 0.18±0.00, Zeta potential was (-28.6±0.66)mV, viscosity was (3.44±0.09)Pa·s; the entrapment efficiency and drug loading were (95.13±2.74)% and (0.47±0.01)%. Rheological tests showed that B-MBG presented classic pseudoplastic fluid characteristics, the viscoelastic modulus would not change with time, the elastic modulus was greater than the viscous modulus, and B-MBG presented a gel state. Under the conditions of high temperature, low temperature and high humidity, the pH, drug content and particle size within 30 d had been proved by the influencing factors to be no significant different for B-MBG. Viscosity was not significantly affected by light, but pH, particle size and content stability were greatly affected by light. Under high temperature and high humidity conditions, the viscosity was proved to be a significant different after 20 d for B-MBG. CONCLUSION The structure is proved to be stable by rheological tests for B-MBG. The stability of B-MBG is affected by light, high temperature and high humidity. It is recommend that B-MBG should be stored at low temperature and protected from light.