Invited Speaker

Self-Assembled Food Mesophases as Delivery Systems in Water Environment: State of the Art & Challenges
Raffaele Mezzenga
Switzerland

In the present talk I will review our personal and other groups contributions to the delivery of active ingredients via self-assembled liquid crystalline mesophases based on water-surfactant systems in the field of food materials. I will present the past work on the use of monoglycerides-based liquid crystals as delivery vehicles and will emphasize our recent quest for the search of alternative molecules to form liquid crystalline mesophases capable to deliver target molecules in water environment. In particular, I will focus on our recent work relating to lyotropic liquid crystals (LC) formed by ternary mixtures of oleoylethanolamide (OEA), water and arginine. OEA, a natural analog of the endogenous cannabinoid anandamide involved in the peripheral regulation of feeding, is selected as a main component of the mesophases due to its capacity to induce efficient decreases in food intake and gains in body mass. Arginine is selected as representative hydrophilic amino acid and added to the OEA-water mixture at different concentrations. The corresponding phase diagrams are determined by combining cross-polarized optical microscopy and small angle X-ray scattering. First, the phase diagram for the OEA-water system is determined. It is shown that these two compounds give rise to reverse Ia3d double gyroid and reverse Pn3m double diamond cubic phases existing in bulk over a large window of temperature and composition, and that for water content beyond 25% Pn3m coexist with excess water. Successively, the influence of arginine as guest molecule in the water channels of the reverse LC is investigated. For the sake of comparison, results for the OEA-water-arginine system are compared with analog series of OEA-water-glucose systems.

The results show that, at a fixed water content and temperature, the phase behavior of the liquid crystalline phases is strongly dependent on arginine concentration. In more detail, arginine can be encapsulated in the bulk OEA-water LC up to 2.0% wt, whereas transitions from Ia3d to Pn3m cubic phase can be observed with increasing arginine concentration. Interestingly, upon an increase of water concentration beyond 20–25%, Pn3m phase starts to coexist with excess water releasing the arginine in external water solution. Quantitative measurements of arginine content inside the LC water channels and in the excess external water solution reveal a complete release of the amino acid, demonstrating that the investigated lyotropic liquid crystalline systems can be used as ideal vehicles for the delivery of functional hydrophilic active molecules in aqueous environment.

References

Mezzenga et al. Nature Materials, 4, 729 (2005)

Mezzenga et al. Curr. Op. Coll. Interf. Sci. 11, 224 (2006)

Mezzenga et al. Biophys. J. 96, 1537 (2009)