Lipid polymorphism in lyotropic liquid crystals for triggered release of bioactives

In this review we present recent progress on lyotropic liquid crystals (LLC) as delivery vehicles for cosmetoceuticals, nutraceuticals, and drugs. LLC have been known for decades and their potential as delivery vehicles is well recognized. Yet, the two major mesophases, reverse hexagonal (H_II) and bicontinuous cubic (primitive, gyroid, and diamond), are relatively hard gels with very slow release kinetics of the bioactives. In recent years a discontinuous cubic micellar mesophase (Q_L) was characterized and studied, showing significant potential as a delivery vehicle. In addition, the H_II mesophase formed could be much more fluid and produced at room temperature. Recent studies concentrated on establishing methods to evaluate solubilization capacity and relationship between the diameter and length of the cylinders and the nature of the solubilizates. Special attention was given to finding methods to target the vehicles to the lumen and to trigger the release of the bioactives. This review summarizes the efforts of our group along with work by numerous other scientists in this area. All these efforts suggest that the lyotropic mesophases and the corresponding dispersed soft particles (cubosomes, hexosomes, micellosomes) are now more than ever ready to become drug delivery vehicles for transport across the skin and the gut.