Structural aspects of a self-emulsifying multifunctional amphiphilic excipient: Part I. The case of Gelucire® 44/14

The use of lipids and lipid-based excipients in self-emulsifying formulations has been widely reported. Such excipients play an important role to improve solubility of poorly soluble drugs and drug candidates. In the current study, we analysed the micellar behavior of a self-emulsifying multifunctional amphiphilic excipient Gelucire® 44/14 at a range of concentrations above the critical micelle concentration (CMC) and at various temperatures using small angle neutron scattering (SANS). At low temperatures, Gelucire® 44/14 was found to form core-shell spherical micelles with an overall radius of ~50 Å, a hydrophobic core radius of ~23 Å and a shell thickness of ~26 Å with a polydispersity of ~20%. The size of the hydrophobic core, and consequently of the overall micelle, was found to increase by less than 10%, with increasing temperature. At concentrations close to its CMC and at the highest temperature studied, the micellar form was transformed to cylindrical or rod-like structures. This study will aid our understanding of how drugs could interact with lipid excipients and how such drug-excipient mixtures behave during manufacturing, storage and after administration.