Preparation and Microstructural Characterization of Griseofulvin Microemulsions Using Different Experimental Methods: SAXS and DSC

The objective of the present study is to formulate and evaluate a new microemulsion (ME) for topical delivery of griseofulvin.
The solubilities of griseofulvin in different combinations of surfactant to cosurfactant (S/Co ratio) were determined. Accordingly, based on their phase diagrams, eight microemulsions were formulated and then evaluated with respect to their particle size, surface tension, viscosity, conductivity, zeta potential and stability. Their release behavior, Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), refractory index (RI), pH and Small-angle-X-ray scattering (SAXS) were also assessed.
The results indicated that the mean droplet size of the MEs ranged from 30.9 to 84.3 nm. Their zeta potential varied from -4.5 to -20.8. Other determined characteristics were viscosity: 254-381 cps, pH: 5.34-6.57, surface tension: 41.16- 42.83 dyne.cm-1, conductivity: 0.0442 – 0.111 ms.cm-1. The drug release was in the range of 22.4 to 43.69 percent. Also, hexagonal, cubic and lamellar liquid crystals were observed in SAXS experiments.
It can be concluded that any alteration in MEs constituents directly affects their microstructure, shape, droplet size and their other physicochemical properties.