Vesicles made by several methods contain the ratio of phospholipids in the stock solution.

Abstract

In this project, we measured the lipid composition of five-component vesicles produced via different methods. When making vesicles, it is typically assumed that the final lipid composition of the vesicles is identical to that of the stock solution. However, it is known that cholesterol incorporates poorly into vesicles made by emulsion phase transfer, and there is some evidence that PE lipids may not fully incorporate into vesicles made by electroformation. Here, we made a stock solution of a five-component mixture of DPPC, DOPC, DLPE, DOPG, and cholesterol. We produced vesicles from this stock solution using some of the most common methods: electroformation, gentle hydration, extrusion, and emulsion phase transfer. We then extracted the lipids from these vesicles using the Bligh and Dyer technique and used mass spectrometry to quantify the amount of each lipid type in the sample. We find that DOPC incorporates less readily into vesicles produced via emulsion phase transfer than other lipids do. For most of the methods we tested, the lipid composition of the vesicles is close to that of the stock solution, implying that results can be compared for vesicles made by these methods.