Liquid-Crystal Based Formulations for Topical Drug Delivery

Abstract

Monoolein, being a biocompatible and bioadhesive penetration enhancer that can form liquid crystalline (LC) phases, possesses remarkable characteristics for addressing drug delivery systems across the biological membrane. A range of formulations based on LC phases were investigated in this study, which includes lamellar, reverse hexagonal, and bicontinuous cubic phases along with an emulsion stabilized by LC phases. Caffeine was chosen as hydophilic model drug to evaluate in vitro release performance. The different monoolein based caffeine formulations were characterized by techniques such as polarized light microscopy, nuclear magnetic resonance (NMR) and small angle x-ray scattering (SAXS). The release experiments, performed through Franz diffusion cells, revealed that the presence of a liquid crystalline (LC) phase prevented burst release in all cases. In addition, taking into consideration that all ingredients are fully biocompatible, the creamy emulsion formulation stabilized by a hexagonal lipid LC phase can be proposed as a challenging preformulation for topical drug delivery.

Keywords:

• Caffeine
• emulsions
• in vitro release
• liquid crystals
• monoolein

Acknowledgments

P. Hiwale acknowledges MIUR for “Young Indian Scientist Fellowships” for the years 2008 and 2009. MIUR Prin 2008 is thanked for financial support. The Scientific Park “POLARIS” (Pula, CA, Italy) is acknowledged for free access to SAXS.

Notes

Mean ± SD.

*Significant difference of slope of release graph for one formulation from different formulations at P < 0.0001.

Designation of different formulations: a: I; b: II; c: III and d: IV.