Phospholipid spherules (liposomes) as a model for biological membranes

TLDR

The lipids, which are in the liquid‑crystal state, trap aqueous solutes such as cations, anions, glucose, or glycine in compartments between a series of lipid bilayers. The review describes the properties of artificial phospholipid spherules composed of phospholipids and various long‑chain anions or cations. The diffusion of solutes from the spherules can be studied in the same way that diffusion across biological membranes is studied. The spherules exhibit ion‑discrimination, osmotic swelling, and responsiveness to steroids, drugs, toxins, and antibiotics, mirroring their effects on erythrocytes, lysosomes, and mitochondria, and thereby serve as a valuable model for studying lipid‑dependent membrane properties.

Abstract

This review describes the properties of artificial spherules composed of phospholipids and various long-chain anions or cations. The lipids, which are in the liquid-crystal state, trap aqueous solutes such as cations, anions, glucose, or glycine in aqueous compartments between a series of lipid bilayers. The diffusion of these solutes from the spherules can be studied in the same way that diffusion across biological membranes is studied. The spherules exhibit many of the properties of natural membrane-bounded structures: they are capable of ion-discrimination, osmotic swelling, and response to a variety of physiologic and pharmacologic agents. These agents (steroids, drugs, toxins, antibiotics) accelerate or retard diffusion of ions or molecules from the spherules in a way that qualitatively mimics their action on erythrocytes, lysosomes, or mitochondria. Thus the spherules constitute a valuable model system with which to study the properties of biological membranes that may be dependent on their lipid components.