Characterisation of bicontinuous cubic liquid crystalline systems of phytantriol and water using cryo field emission scanning electron microscopy (cryo FESEM)

Abstract

Cubosomes are a novel lipid particulate delivery system currently being investigated for drug delivery purposes. The present study investigates bicontinuous cubic liquid crystalline systems (bulk phase and cubosomes) formed by phytantriol and water using cryo field emission scanning electron microscopy (cryo FESEM). Previously cubosomes have been characterized by cryo transmission electron microscopy (cryo TEM) with small angle X-ray diffraction (SAXS) confirming the bicontinuous liquid crystalline type. Bulk cubic phase and cubosomes were prepared from phytantriol and Pluronic F127 and analysed using cryo FESEM and SAXS. The micrographs showed the cubic phase had a tortuous, bicontinuous nature with a non-intersecting network of water channels. The cubosomes also show the same underlying tortuous structure entirely consistent with that of the bulk cubic phase and closely resemble the mathematical description of cubosomes described using nodal surface representation. The structure of both systems was confirmed using SAXS as a bicontinuous cubic liquid crystalline phase with Pn3 m geometry. Cryo FESEM provides valuable insights into the morphological features of bicontinuous cubic liquid crystalline systems. The unique details shown provide strength to support the nodal surface representation of bicontinuous cubic liquid crystalline systems. Cryo FESEM provides a new technique to complement cryo TEM and SAXS for investigating their structure and function.