(4od) Triglycerides Stabilize Water/Organic Interfaces of Changing Area Via Conformational Flexibility

The role of Triglycerides (TGs) in both natural and synthetic biological membranes has long been the subject of study, involving metabolism, disease, and colloidal synthesis. TGs have been found to be critical components for successful liposomal encapsulation via Water/Oil/Water double emulsion, which this work endeavors to explain.

TGs can occupy multiple positions in biological membranes. The glycerol backbone can reside at the Water/Organic interface, adjacent to phospholipid headgroups (“m” conformation), typically with relatively low (<3%) solubility. The glycerol backbone can also occupy hydrophobic regions, where it is isolated from water (“h” or “oil” conformation). This can occur either mid-membrane positions or phospholipid-coated lipid droplets (LDs). These conformations can be distinguished using 13C-Nuclear Magnetic Resonance Spectroscopy (NMR), which determines the degree of hydration of the TG backbone.

Using this method, it was revealed that TGs transition from “m” to “h” conformation as the organic solvent is removed via evaporation. A new, transitional TG backbone position has been identified, with a level of hydration between “m” and “h”. These results suggest that TGs are able to temporarily coat and stabilize the large water/organic interfaces present after emulsification. As the organic solvent is removed and interfaces shrink, the TGs recede into mid-membrane spaces or bud off into Lipid Droplets (LDs), which are confirmed via Transmission Electron Microscopy (TEM) and can be removed via centrifugation. Encapsulation efficiency is found to be inversely related to both the saturation and length of the TG acyl chains, indicating that membrane fluidization is a key property arising from the presence of TGs. Beyond clarification of a mechanism for high-efficiency liposomal encapsulation, these results implicate TGs as components that are able to stabilize biological membrane transitions involving changing interfacial area and curvature. This role for TGs may be of use in the formulation of drug delivery systems, as well as in the investigation of membrane transitions in life sciences.

Research Interests: Colloid Science, Biological Membranes, Drug Delivery, Synthetic Biology, Ultrasound, Fluorescence Spectroscopy, Biological Fluorescence