Solid state characterisation of a dry emulsion: a potential drug delivery system

Abstract

Dry emulsions were prepared by spray drying liquid emulsions in a laboratory spray dryer. Lactose alone, and lactose in combination with maltodextrine, was used as a water soluble, solid carrier. Sodium caseinate was used as emulsifying agent and griseofulvin was used as an oil soluble model drug substance in very low concentration. Different fats were applied; soybean oil (liquid), hardened coconut oil (semisolid) and hardened rapeseed oil, being solid at room temperature. The surface of the powder particles was mainly made up of sodium caseinate, while the core was made up of fat dispersed in a carrier matrix of amorphous lactose. Amorphous lactose is very sensitive to moisture, and during moisture uptake recrystallisation of lactose takes place and the physical structure of the powder particle was changed. By addition of maltodextrine as carrier, the physical structure of the spray dried powders was tried to be maintained during recrystallisation of lactose. Reconstitution properties of the spray dried powders were investigated and correlated to solid state characterisation of the powders performed by Scanning Electron Microscope (SEM), Differential Scanning Calorimetry (DSC), X-ray powder diffraction and Electron Spectroscopy for Chemical Analysis (ESCA).