Role of Colloidal Silicon Dioxide in Eudragit<i> In-Situ </i>Forming Gel

Abstract

Colloidal silicon dioxide (Aerosil) is fumed silica that has been used as gelling agents, thickening agents and filling agents. The objectives of this study were to characterize the effect of hydrophilic (aerosil 200) and hydrophobic (aerosil R972) colloidal silicon dioxide on physical properties of eudragit gels which N-methyl-pyrrolidone was employed as dispersing medium. The samples were investigated in terms of viscosity, rheology and syringeability. The results indicated that the aerosil 200 and aerosil R972 amount influenced the viscosity, rheology and syringeability of the prepared gels. Viscosity and syringeability of the systems were increased with an increased amount of both aerosils. However, the viscosity and syringeability of the prepared gels containing aerosil 200 were increased higher than that of systems containing aerosil R972. The rheological behaviors of all systems consisting aerosil 200 and R972 were non-Newtonian flow. These studies demonstrated that aerosil 200 and R972 could improve the physical properties of eudragit gels dispersed in N-methyl-pyrrolidone.