Asymmetric Unilamellar Vesicles Research Articles

Assembly methods for asymmetric lipid and polymer-lipid vesicles.

Asymmetric unilamellar vesicles are aqueous bodies surrounded by two dissimilar leaflets made from lipids, polymers, or both. They are great models for cell membranes and attractive vehicles in potential biomedicine applications. Despite their promise, asymmetric unilamellar vesicles are not widely studied or adopted in applications. This is largely due to the complexity in generating asymmetric membranes. Recent technical advances in microfluidics have opened doors to high throughput fabrication of asymmetric unilamellar vesicles. In this review, we focus on microfluidic methods for generating asymmetric lipid vesicles, with two dissimilar lipid leaflets, and asymmetric lipid-polymer vesicles, with one lipid leaflet and one polymer leaflet. We also review a few standard non-microfluidic methods for generating asymmetric vesicles. We hope to highlight the improved capability in obtaining asymmetric vesicles through a variety of methods and encourage the wider scientific community to adopt some of these for their own work.

Short-chain lecithin/long-chain phospholipid unilamellar vesicles: asymmetry, dynamics, and enzymatic hydrolysis of the short-chain component.

Asymmetric unilamellar vesicles are produced when short-chain phospholipids (fatty acyl chain lengths of 6-8 carbons) are mixed with long-chain phospholipids (fatty acyl chain lengths of 14 carbons or longer) in ratios of 1:4 short-chain/long-chain component. Short-chain lecithins are preferentially distributed on the outer monolayer, while a short-chain phosphatidylethanolamine derivative appears to localize on the inner monolayer of these spontaneously forming vesicles. Lanthanide NMR shift experiments clearly show a difference in head-group/ion interactions between the short-chain and long-chain species. Two-dimensional 1H NMR studies reveal efficient spin diffusion networks for the short-chain species embedded in the long-chain bilayer matrix. The short-chain lecithin is considerably more mobile than the long-chain component but has hindered motion compared to short-chain lecithin micelles. This differentiation in physical characteristics of the two phospholipid components is critical to understanding the activity of phospholipases toward these binary systems.