Abstract
Preparation of monodisperse vesicles is important both for research purposes and for practical applications. While the extrusion of vesicles through small pores (∼100 nm in diameter) results in relatively uniform populations of vesicles, extrusion to larger sizes results in very heterogeneous populations of vesicles. Here we report a simple method for preparing large monodisperse multilamellar vesicles through a combination of extrusion and large-pore dialysis. For example, extrusion of polydisperse vesicles through 5-µm-diameter pores eliminates vesicles larger than 5 µm in diameter. Dialysis of extruded vesicles against 3-µm-pore-size polycarbonate membranes eliminates vesicles smaller than 3 µm in diameter, leaving behind a population of monodisperse vesicles with a mean diameter of ∼4 µm. The simplicity of this method makes it an effective tool for laboratory vesicle preparation with potential applications in preparing large monodisperse liposomes for drug delivery.
Highlights
Vesicles are closed bilayer membranes that encapsulate an aqueous compartment
In studies of vesicle growth, monodisperse vesicle preparations allow for the detection of changes in vesicle size by light scattering or by fluorescence microscopy [2,4]
The extrusion-dialysis method for preparing monodisperse vesicles that we have described is a hybrid preparation/ purification method in which extrusion is used to prepare vesicles that are smaller than a given size, and dialysis is used to eliminate vesicles smaller than a desired size threshold
Summary
Fatty acid vesicles have been studied as a model system for primitive cellular membranes at the origin of life [1,2]. Phospholipid vesicles (liposomes), which are more stable under physiological conditions, have been widely used for drug delivery [3]. In studies of vesicle growth, monodisperse vesicle preparations allow for the detection of changes in vesicle size by light scattering or by fluorescence microscopy [2,4]. The size distribution of vesicles is a crucial factor in determining the efficacy of drug delivery [5]. The accumulation of liposomes in tumors is size-dependent, as tumor capillaries have larger pores (100 to 700 nm in diameter) than normal blood vessels (typically, nm). The drug release profile from liposomes in vivo has been shown to be size-dependent [7]. For inhaled liposomal drug delivery, the ideal liposome size is between 1 and 3 mm [8,9,10], because particles in this size range can be delivered into the deep lung more effectively and avoid phagocytic clearance from the lung periphery [9]
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